rfc4646.txt   rfc5646.txt 
Network Working Group A. Phillips, Ed. Network Working Group A. Phillips, Ed.
Request for Comments: 4646 Yahoo! Inc. Request for Comments: 5646 Lab126
BCP: 47 M. Davis, Ed. BCP: 47 M. Davis, Ed.
Obsoletes: 3066 Google Obsoletes: 4646 Google
Category: Best Current Practice September 2006 Category: Best Current Practice September 2009
Tags for Identifying Languages Tags for Identifying Languages
Abstract
This document describes the structure, content, construction, and
semantics of language tags for use in cases where it is desirable to
indicate the language used in an information object. It also
describes how to register values for use in language tags and the
creation of user-defined extensions for private interchange.
Status of This Memo Status of This Memo
This document specifies an Internet Best Current Practices for the This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited. improvements. Distribution of this memo is unlimited.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
Abstract This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
This document describes the structure, content, construction, and This document may contain material from IETF Documents or IETF
semantics of language tags for use in cases where it is desirable to Contributions published or made publicly available before November
indicate the language used in an information object. It also 10, 2008. The person(s) controlling the copyright in some of this
describes how to register values for use in language tags and the material may not have granted the IETF Trust the right to allow
creation of user-defined extensions for private interchange. This modifications of such material outside the IETF Standards Process.
document, in combination with RFC 4647, replaces RFC 3066, which Without obtaining an adequate license from the person(s) controlling
replaced RFC 1766. the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents Table of Contents
1. Introduction ....................................................3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Language Tag ................................................4 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Syntax .....................................................4 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Language Subtag Sources and Interpretation .................7 2.1.1. Formatting of Language Tags . . . . . . . . . . . . . 6
2.2.1. Primary Language Subtag .............................8 2.2. Language Subtag Sources and Interpretation . . . . . . . . 8
2.2.2. Extended Language Subtags ..........................10 2.2.1. Primary Language Subtag . . . . . . . . . . . . . . . . 9
2.2.3. Script Subtag ......................................11 2.2.2. Extended Language Subtags . . . . . . . . . . . . . . 11
2.2.4. Region Subtag ......................................11 2.2.3. Script Subtag . . . . . . . . . . . . . . . . . . . . 12
2.2.5. Variant Subtags ....................................13 2.2.4. Region Subtag . . . . . . . . . . . . . . . . . . . . 13
2.2.6. Extension Subtags ..................................14 2.2.5. Variant Subtags . . . . . . . . . . . . . . . . . . . 15
2.2.7. Private Use Subtags ................................16 2.2.6. Extension Subtags . . . . . . . . . . . . . . . . . . 16
2.2.8. Preexisting RFC 3066 Registrations .................16 2.2.7. Private Use Subtags . . . . . . . . . . . . . . . . . 18
2.2.9. Classes of Conformance .............................17 2.2.8. Grandfathered and Redundant Registrations . . . . . . 18
3. Registry Format and Maintenance ................................18 2.2.9. Classes of Conformance . . . . . . . . . . . . . . . . 19
3.1. Format of the IANA Language Subtag Registry ...............18 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 21
3.2. Language Subtag Reviewer ..................................24 3.1. Format of the IANA Language Subtag Registry . . . . . . . 21
3.3. Maintenance of the Registry ...............................24 3.1.1. File Format . . . . . . . . . . . . . . . . . . . . . 21
3.4. Stability of IANA Registry Entries ........................25 3.1.2. Record and Field Definitions . . . . . . . . . . . . . 23
3.5. Registration Procedure for Subtags ........................29 3.1.3. Type Field . . . . . . . . . . . . . . . . . . . . . . 26
3.6. Possibilities for Registration ............................32 3.1.4. Subtag and Tag Fields . . . . . . . . . . . . . . . . 26
3.7. Extensions and Extensions Registry ........................34 3.1.5. Description Field . . . . . . . . . . . . . . . . . . 26
3.8. Initialization of the Registries ..........................37 3.1.6. Deprecated Field . . . . . . . . . . . . . . . . . . . 28
4. Formation and Processing of Language Tags ......................38 3.1.7. Preferred-Value Field . . . . . . . . . . . . . . . . 28
4.1. Choice of Language Tag ....................................38 3.1.8. Prefix Field . . . . . . . . . . . . . . . . . . . . . 31
4.2. Meaning of the Language Tag ...............................40 3.1.9. Suppress-Script Field . . . . . . . . . . . . . . . . 32
4.3. Length Considerations .....................................41 3.1.10. Macrolanguage Field . . . . . . . . . . . . . . . . . 32
4.3.1. Working with Limited Buffer Sizes ..................42 3.1.11. Scope Field . . . . . . . . . . . . . . . . . . . . . 33
4.3.2. Truncation of Language Tags ........................43 3.1.12. Comments Field . . . . . . . . . . . . . . . . . . . . 34
4.4. Canonicalization of Language Tags .........................44 3.2. Language Subtag Reviewer . . . . . . . . . . . . . . . . . 35
4.5. Considerations for Private Use Subtags ....................45 3.3. Maintenance of the Registry . . . . . . . . . . . . . . . 35
5. IANA Considerations ............................................46 3.4. Stability of IANA Registry Entries . . . . . . . . . . . . 36
5.1. Language Subtag Registry ..................................46 3.5. Registration Procedure for Subtags . . . . . . . . . . . . 41
5.2. Extensions Registry .......................................47 3.6. Possibilities for Registration . . . . . . . . . . . . . . 46
6. Security Considerations ........................................48 3.7. Extensions and the Extensions Registry . . . . . . . . . . 49
7. Character Set Considerations ...................................48 3.8. Update of the Language Subtag Registry . . . . . . . . . . 52
8. Changes from RFC 3066 ..........................................49 3.9. Applicability of the Subtag Registry . . . . . . . . . . . 52
9. References .....................................................52 4. Formation and Processing of Language Tags . . . . . . . . . . 53
9.1. Normative References ......................................52 4.1. Choice of Language Tag . . . . . . . . . . . . . . . . . . 53
9.2. Informative References ....................................53 4.1.1. Tagging Encompassed Languages . . . . . . . . . . . . 58
Appendix A. Acknowledgements ......................................55 4.1.2. Using Extended Language Subtags . . . . . . . . . . . 59
Appendix B. Examples of Language Tags (Informative) ...............56 4.2. Meaning of the Language Tag . . . . . . . . . . . . . . . 61
4.3. Lists of Languages . . . . . . . . . . . . . . . . . . . . 63
4.4. Length Considerations . . . . . . . . . . . . . . . . . . 63
4.4.1. Working with Limited Buffer Sizes . . . . . . . . . . 64
4.4.2. Truncation of Language Tags . . . . . . . . . . . . . 65
4.5. Canonicalization of Language Tags . . . . . . . . . . . . 66
4.6. Considerations for Private Use Subtags . . . . . . . . . . 68
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 69
5.1. Language Subtag Registry . . . . . . . . . . . . . . . . . 69
5.2. Extensions Registry . . . . . . . . . . . . . . . . . . . 71
6. Security Considerations . . . . . . . . . . . . . . . . . . . 71
7. Character Set Considerations . . . . . . . . . . . . . . . . . 72
8. Changes from RFC 4646 . . . . . . . . . . . . . . . . . . . . 73
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 76
9.1. Normative References . . . . . . . . . . . . . . . . . . . 76
9.2. Informative References . . . . . . . . . . . . . . . . . . 78
Appendix A. Examples of Language Tags (Informative) . . . . . . . 80
Appendix B. Examples of Registration Forms . . . . . . . . . . . 82
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 83
1. Introduction 1. Introduction
Human beings on our planet have, past and present, used a number of Human beings on our planet have, past and present, used a number of
languages. There are many reasons why one would want to identify the languages. There are many reasons why one would want to identify the
language used when presenting or requesting information. language used when presenting or requesting information.
A user's language preferences often need to be identified so that The language of an information item or a user's language preferences
appropriate processing can be applied. For example, the user's often need to be identified so that appropriate processing can be
language preferences in a Web browser can be used to select Web pages applied. For example, the user's language preferences in a Web
appropriately. Language preferences can also be used to select among browser can be used to select Web pages appropriately. Language
tools (such as dictionaries) to assist in the processing or information can also be used to select among tools (such as
understanding of content in different languages. dictionaries) to assist in the processing or understanding of content
in different languages. Knowledge about the particular language used
In addition, knowledge about the particular language used by some by some piece of information content might be useful or even required
piece of information content might be useful or even required by some by some types of processing, for example, spell-checking, computer-
types of processing; for example, spell-checking, computer-
synthesized speech, Braille transcription, or high-quality print synthesized speech, Braille transcription, or high-quality print
renderings. renderings.
One means of indicating the language used is by labeling the One means of indicating the language used is by labeling the
information content with an identifier or "tag". These tags can be information content with an identifier or "tag". These tags can also
used to specify user preferences when selecting information content, be used to specify the user's preferences when selecting information
or for labeling additional attributes of content and associated content or to label additional attributes of content and associated
resources. resources.
Tags can also be used to indicate additional language attributes of Sometimes language tags are used to indicate additional language
content. For example, indicating specific information about the attributes of content. For example, indicating specific information
dialect, writing system, or orthography used in a document or about the dialect, writing system, or orthography used in a document
resource may enable the user to obtain information in a form that or resource may enable the user to obtain information in a form that
they can understand, or it can be important in processing or they can understand, or it can be important in processing or
rendering the given content into an appropriate form or style. rendering the given content into an appropriate form or style.
This document specifies a particular identifier mechanism (the This document specifies a particular identifier mechanism (the
language tag) and a registration function for values to be used to language tag) and a registration function for values to be used to
form tags. It also defines a mechanism for private use values and form tags. It also defines a mechanism for private use values and
future extension. future extensions.
This document, in combination with [RFC4647], replaces [RFC3066], This document replaces [RFC4646] (which obsoleted [RFC3066] which, in
which replaced [RFC1766]. For a list of changes in this document, turn, replaced [RFC1766]). This document, in combination with
[RFC4647], comprises BCP 47. For a list of changes in this document,
see Section 8. see Section 8.
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. The Language Tag 2. The Language Tag
Language tags are used to help identify languages, whether spoken, Language tags are used to help identify languages, whether spoken,
written, signed, or otherwise signaled, for the purpose of written, signed, or otherwise signaled, for the purpose of
communication. This includes constructed and artificial languages, communication. This includes constructed and artificial languages
but excludes languages not intended primarily for human but excludes languages not intended primarily for human
communication, such as programming languages. communication, such as programming languages.
2.1. Syntax 2.1. Syntax
The language tag is composed of one or more parts, known as A language tag is composed from a sequence of one or more "subtags",
"subtags". Each subtag consists of a sequence of alphanumeric each of which refines or narrows the range of language identified by
characters. Subtags are distinguished and separated from one another the overall tag. Subtags, in turn, are a sequence of alphanumeric
by a hyphen ("-", ABNF [RFC4234] %x2D). A language tag consists of a characters (letters and digits), distinguished and separated from
"primary language" subtag and a (possibly empty) series of subsequent other subtags in a tag by a hyphen ("-", [Unicode] U+002D).
subtags, each of which refines or narrows the range of languages
identified by the overall tag.
Usually, each type of subtag is distinguished by length, position in There are different types of subtag, each of which is distinguished
the tag, and content: subtags can be recognized solely by these by length, position in the tag, and content: each subtag's type can
features. The only exception to this is a fixed list of be recognized solely by these features. This makes it possible to
grandfathered tags registered under RFC 3066 [RFC3066]. This makes extract and assign some semantic information to the subtags, even if
it possible to construct a parser that can extract and assign some the specific subtag values are not recognized. Thus, a language tag
semantic information to the subtags, even if the specific subtag processor need not have a list of valid tags or subtags (that is, a
values are not recognized. Thus, a parser need not have an up-to- copy of some version of the IANA Language Subtag Registry) in order
date copy (or any copy at all) of the subtag registry to perform most to perform common searching and matching operations. The only
searching and matching operations. exceptions to this ability to infer meaning from subtag structure are
the grandfathered tags listed in the productions 'regular' and
'irregular' below. These tags were registered under [RFC3066] and
are a fixed list that can never change.
The syntax of the language tag in ABNF [RFC4234] is: The syntax of the language tag in ABNF [RFC5234] is:
Language-Tag = langtag Language-Tag = langtag ; normal language tags
/ privateuse ; private use tag / privateuse ; private use tag
/ grandfathered ; grandfathered registrations / grandfathered ; grandfathered tags
langtag = (language langtag = language
["-" script] ["-" script]
["-" region] ["-" region]
*("-" variant) *("-" variant)
*("-" extension) *("-" extension)
["-" privateuse]) ["-" privateuse]
language = (2*3ALPHA [ extlang ]) ; shortest ISO 639 code language = 2*3ALPHA ; shortest ISO 639 code
/ 4ALPHA ; reserved for future use ["-" extlang] ; sometimes followed by
/ 5*8ALPHA ; registered language subtag ; extended language subtags
/ 4ALPHA ; or reserved for future use
/ 5*8ALPHA ; or registered language subtag
extlang = *3("-" 3ALPHA) ; reserved for future use extlang = 3ALPHA ; selected ISO 639 codes
*2("-" 3ALPHA) ; permanently reserved
script = 4ALPHA ; ISO 15924 code script = 4ALPHA ; ISO 15924 code
region = 2ALPHA ; ISO 3166 code region = 2ALPHA ; ISO 3166-1 code
/ 3DIGIT ; UN M.49 code / 3DIGIT ; UN M.49 code
variant = 5*8alphanum ; registered variants variant = 5*8alphanum ; registered variants
/ (DIGIT 3alphanum) / (DIGIT 3alphanum)
extension = singleton 1*("-" (2*8alphanum)) extension = singleton 1*("-" (2*8alphanum))
singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT ; Single alphanumerics
; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" ; "x" reserved for private use
; Single letters: x/X is reserved for private use singleton = DIGIT ; 0 - 9
/ %x41-57 ; A - W
/ %x59-5A ; Y - Z
/ %x61-77 ; a - w
/ %x79-7A ; y - z
privateuse = ("x"/"X") 1*("-" (1*8alphanum)) privateuse = "x" 1*("-" (1*8alphanum))
grandfathered = 1*3ALPHA 1*2("-" (2*8alphanum)) grandfathered = irregular ; non-redundant tags registered
; grandfathered registration / regular ; during the RFC 3066 era
; Note: i is the only singleton
; that starts a grandfathered tag
alphanum = (ALPHA / DIGIT) ; letters and numbers irregular = "en-GB-oed" ; irregular tags do not match
/ "i-ami" ; the 'langtag' production and
/ "i-bnn" ; would not otherwise be
/ "i-default" ; considered 'well-formed'
/ "i-enochian" ; These tags are all valid,
/ "i-hak" ; but most are deprecated
/ "i-klingon" ; in favor of more modern
/ "i-lux" ; subtags or subtag
/ "i-mingo" ; combination
/ "i-navajo"
/ "i-pwn"
/ "i-tao"
/ "i-tay"
/ "i-tsu"
/ "sgn-BE-FR"
/ "sgn-BE-NL"
/ "sgn-CH-DE"
regular = "art-lojban" ; these tags match the 'langtag'
/ "cel-gaulish" ; production, but their subtags
/ "no-bok" ; are not extended language
/ "no-nyn" ; or variant subtags: their meaning
/ "zh-guoyu" ; is defined by their registration
/ "zh-hakka" ; and all of these are deprecated
/ "zh-min" ; in favor of a more modern
/ "zh-min-nan" ; subtag or sequence of subtags
/ "zh-xiang"
alphanum = (ALPHA / DIGIT) ; letters and numbers
Figure 1: Language Tag ABNF Figure 1: Language Tag ABNF
Note: There is a subtlety in the ABNF for 'variant': variants For examples of language tags, see Appendix A.
starting with a digit MAY be four characters long, while those
starting with a letter MUST be at least five characters long.
All subtags have a maximum length of eight characters and whitespace All subtags have a maximum length of eight characters. Whitespace is
is not permitted in a language tag. For examples of language tags, not permitted in a language tag. There is a subtlety in the ABNF
see Appendix B. production 'variant': a variant starting with a digit has a minimum
length of four characters, while those starting with a letter have a
minimum length of five characters.
Note that although [RFC4234] refers to octets, the language tags Although [RFC5234] refers to octets, the language tags described in
described in this document are sequences of characters from the this document are sequences of characters from the US-ASCII [ISO646]
US-ASCII [ISO646] repertoire. Language tags MAY be used in documents repertoire. Language tags MAY be used in documents and applications
and applications that use other encodings, so long as these encompass that use other encodings, so long as these encompass the relevant
the US-ASCII repertoire. An example of this would be an XML document part of the US-ASCII repertoire. An example of this would be an XML
that uses the UTF-16LE [RFC2781] encoding of [Unicode]. document that uses the UTF-16LE [RFC2781] encoding of [Unicode].
The tags and their subtags, including private use and extensions, are 2.1.1. Formatting of Language Tags
to be treated as case insensitive: there exist conventions for the
capitalization of some of the subtags, but these MUST NOT be taken to
carry meaning.
For example: At all times, language tags and their subtags, including private use
and extensions, are to be treated as case insensitive: there exist
conventions for the capitalization of some of the subtags, but these
MUST NOT be taken to carry meaning.
Thus, the tag "mn-Cyrl-MN" is not distinct from "MN-cYRL-mn" or "mN-
cYrL-Mn" (or any other combination), and each of these variations
conveys the same meaning: Mongolian written in the Cyrillic script as
used in Mongolia.
The ABNF syntax also does not distinguish between upper- and
lowercase: the uppercase US-ASCII letters in the range 'A' through
'Z' are always considered equivalent and mapped directly to their US-
ASCII lowercase equivalents in the range 'a' through 'z'. So the tag
"I-AMI" is considered equivalent to that value "i-ami" in the
'irregular' production.
Although case distinctions do not carry meaning in language tags,
consistent formatting and presentation of language tags will aid
users. The format of subtags in the registry is RECOMMENDED as the
form to use in language tags. This format generally corresponds to
the common conventions for the various ISO standards from which the
subtags are derived.
These conventions include:
o [ISO639-1] recommends that language codes be written in lowercase o [ISO639-1] recommends that language codes be written in lowercase
('mn' Mongolian). ('mn' Mongolian).
o [ISO3166-1] recommends that country codes be capitalized ('MN'
Mongolia).
o [ISO15924] recommends that script codes use lowercase with the o [ISO15924] recommends that script codes use lowercase with the
initial letter capitalized ('Cyrl' Cyrillic). initial letter capitalized ('Cyrl' Cyrillic).
However, in the tags defined by this document, the uppercase US-ASCII o [ISO3166-1] recommends that country codes be capitalized ('MN'
letters in the range 'A' through 'Z' are considered equivalent and Mongolia).
mapped directly to their US-ASCII lowercase equivalents in the range
'a' through 'z'. Thus, the tag "mn-Cyrl-MN" is not distinct from
"MN-cYRL-mn" or "mN-cYrL-Mn" (or any other combination), and each of
these variations conveys the same meaning: Mongolian written in the
Cyrillic script as used in Mongolia.
Although case distinctions do not carry meaning in language tags, An implementation can reproduce this format without accessing the
consistent formatting and presentation of the tags will aid users. registry as follows. All subtags, including extension and private
The format of the tags and subtags in the registry is RECOMMENDED. use subtags, use lowercase letters with two exceptions: two-letter
In this format, all non-initial two-letter subtags are uppercase, all and four-letter subtags that neither appear at the start of the tag
non-initial four-letter subtags are titlecase, and all other subtags nor occur after singletons. Such two-letter subtags are all
are lowercase. uppercase (as in the tags "en-CA-x-ca" or "sgn-BE-FR") and four-
letter subtags are titlecase (as in the tag "az-Latn-x-latn").
Note: Case folding of ASCII letters in certain locales, unless
carefully handled, sometimes produces non-ASCII character values.
The Unicode Character Database file "SpecialCasing.txt"
[SpecialCasing] defines the specific cases that are known to cause
problems with this. In particular, the letter 'i' (U+0069) in
Turkish and Azerbaijani is uppercased to U+0130 (LATIN CAPITAL LETTER
I WITH DOT ABOVE). Implementers SHOULD specify a locale-neutral
casing operation to ensure that case folding of subtags does not
produce this value, which is illegal in language tags. For example,
if one were to uppercase the region subtag 'in' using Turkish locale
rules, the sequence U+0130 U+004E would result, instead of the
expected 'IN'.
2.2. Language Subtag Sources and Interpretation 2.2. Language Subtag Sources and Interpretation
The namespace of language tags and their subtags is administered by The namespace of language tags and their subtags is administered by
the Internet Assigned Numbers Authority (IANA) [RFC2860] according to the Internet Assigned Numbers Authority (IANA) according to the rules
the rules in Section 5 of this document. The Language Subtag in Section 5 of this document. The Language Subtag Registry
Registry maintained by IANA is the source for valid subtags: other maintained by IANA is the source for valid subtags: other standards
standards referenced in this section provide the source material for referenced in this section provide the source material for that
that registry. registry.
Terminology in this section: Terminology used in this document:
o Tag or tags refers to a complete language tag, such as o "Tag" refers to a complete language tag, such as "sr-Latn-RS" or
"fr-Latn-CA". Examples of tags in this document are enclosed in "az-Arab-IR". Examples of tags in this document are enclosed in
double-quotes ("en-US"). double-quotes ("en-US").
o Subtag refers to a specific section of a tag, delimited by hyphen, o "Subtag" refers to a specific section of a tag, delimited by a
such as the subtag 'Latn' in "fr-Latn-CA". Examples of subtags in hyphen, such as the subtags 'zh', 'Hant', and 'CN' in the tag "zh-
this document are enclosed in single quotes ('Latn'). Hant-CN". Examples of subtags in this document are enclosed in
single quotes ('Hant').
o Code or codes refers to values defined in external standards (and
that are used as subtags in this document). For example, 'Latn'
is an [ISO15924] script code that was used to define the 'Latn'
script subtag for use in a language tag. Examples of codes in
this document are enclosed in single quotes ('en', 'Latn').
The definitions in this section apply to the various subtags within o "Code" refers to values defined in external standards (and that
the language tags defined by this document, excepting those are used as subtags in this document). For example, 'Hant' is an
"grandfathered" tags defined in Section 2.2.8. [ISO15924] script code that was used to define the 'Hant' script
subtag for use in a language tag. Examples of codes in this
document are enclosed in single quotes ('en', 'Hant').
Language tags are designed so that each subtag type has unique length Language tags are designed so that each subtag type has unique length
and content restrictions. These make identification of the subtag's and content restrictions. These make identification of the subtag's
type possible, even if the content of the subtag itself is type possible, even if the content of the subtag itself is
unrecognized. This allows tags to be parsed and processed without unrecognized. This allows tags to be parsed and processed without
reference to the latest version of the underlying standards or the reference to the latest version of the underlying standards or the
IANA registry and makes the associated exception handling when IANA registry and makes the associated exception handling when
parsing tags simpler. parsing tags simpler.
Subtags in the IANA registry that do not come from an underlying Some of the subtags in the IANA registry do not come from an
standard can only appear in specific positions in a tag. underlying standard. These can only appear in specific positions in
Specifically, they can only occur as primary language subtags or as a tag: they can only occur as primary language subtags or as variant
variant subtags. subtags.
Note that sequences of private use and extension subtags MUST occur Sequences of private use and extension subtags MUST occur at the end
at the end of the sequence of subtags and MUST NOT be interspersed of the sequence of subtags and MUST NOT be interspersed with subtags
with subtags defined elsewhere in this document. defined elsewhere in this document. These sequences are introduced
by single-character subtags, which are reserved as follows:
Single-letter and single-digit subtags are reserved for current or o The single-letter subtag 'x' introduces a sequence of private use
future use. These include the following current uses: subtags. The interpretation of any private use subtag is defined
solely by private agreement and is not defined by the rules in
this section or in any standard or registry defined in this
document.
o The single-letter subtag 'x' is reserved to introduce a sequence o The single-letter subtag 'i' is used by some grandfathered tags,
of private use subtags. The interpretation of any private use such as "i-default", where it always appears in the first position
subtags is defined solely by private agreement and is not defined and cannot be confused with an extension.
by the rules in this section or in any standard or registry
defined in this document.
o All other single-letter subtags are reserved to introduce o All other single-letter and single-digit subtags are reserved to
standardized extension subtag sequences as described in introduce standardized extension subtag sequences as described in
Section 3.7. Section 3.7.
The single-letter subtag 'i' is used by some grandfathered tags, such
as "i-enochian", where it always appears in the first position and
cannot be confused with an extension.
2.2.1. Primary Language Subtag 2.2.1. Primary Language Subtag
The primary language subtag is the first subtag in a language tag The primary language subtag is the first subtag in a language tag and
(with the exception of private use and certain grandfathered tags) cannot be omitted, with two exceptions:
and cannot be omitted. The following rules apply to the primary
language subtag:
1. All two-character language subtags were defined in the IANA o The single-character subtag 'x' as the primary subtag indicates
registry according to the assignments found in the standard ISO that the language tag consists solely of subtags whose meaning is
639 Part 1, "ISO 639-1:2002, Codes for the representation of defined by private agreement. For example, in the tag "x-fr-CH",
names of languages -- Part 1: Alpha-2 code" [ISO639-1], or using the subtags 'fr' and 'CH' do not represent the French language or
assignments subsequently made by the ISO 639 Part 1 maintenance the country of Switzerland (or any other value in the IANA
agency or governing standardization bodies. registry) unless there is a private agreement in place to do so.
See Section 4.6.
2. All three-character language subtags were defined in the IANA o The single-character subtag 'i' is used by some grandfathered tags
registry according to the assignments found in ISO 639 Part 2, (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other
"ISO 639-2:1998 - Codes for the representation of names of grandfathered tags have a primary language subtag in their first
languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2], or position.)
assignments subsequently made by the ISO 639 Part 2 maintenance
agency or governing standardization bodies. The following rules apply to the primary language subtag:
1. Two-character primary language subtags were defined in the IANA
registry according to the assignments found in the standard "ISO
639-1:2002, Codes for the representation of names of languages --
Part 1: Alpha-2 code" [ISO639-1], or using assignments
subsequently made by the ISO 639-1 registration authority (RA) or
governing standardization bodies.
2. Three-character primary language subtags in the IANA registry
were defined according to the assignments found in one of these
additional ISO 639 parts or assignments subsequently made by the
relevant ISO 639 registration authorities or governing
standardization bodies:
A. "ISO 639-2:1998 - Codes for the representation of names of
languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2]
B. "ISO 639-3:2007 - Codes for the representation of names of
languages -- Part 3: Alpha-3 code for comprehensive coverage
of languages" [ISO639-3]
C. "ISO 639-5:2008 - Codes for the representation of names of
languages -- Part 5: Alpha-3 code for language families and
groups" [ISO639-5]
3. The subtags in the range 'qaa' through 'qtz' are reserved for 3. The subtags in the range 'qaa' through 'qtz' are reserved for
private use in language tags. These subtags correspond to codes private use in language tags. These subtags correspond to codes
reserved by ISO 639-2 for private use. These codes MAY be used reserved by ISO 639-2 for private use. These codes MAY be used
for non-registered primary language subtags (instead of using for non-registered primary language subtags (instead of using
private use subtags following 'x-'). Please refer to Section 4.5 private use subtags following 'x-'). Please refer to Section 4.6
for more information on private use subtags. for more information on private use subtags.
4. All four-character language subtags are reserved for possible 4. Four-character language subtags are reserved for possible future
future standardization. standardization.
5. All language subtags of 5 to 8 characters in length in the IANA
registry were defined via the registration process in Section 3.5
and MAY be used to form the primary language subtag. At the time
this document was created, there were no examples of this kind of
subtag and future registrations of this type will be discouraged:
primary languages are strongly RECOMMENDED for registration with
ISO 639, and proposals rejected by ISO 639/RA will be closely
scrutinized before they are registered with IANA.
6. The single-character subtag 'x' as the primary subtag indicates 5. Any language subtags of five to eight characters in length in the
that the language tag consists solely of subtags whose meaning is IANA registry were defined via the registration process in
defined by private agreement. For example, in the tag "x-fr-CH", Section 3.5 and MAY be used to form the primary language subtag.
the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the An example of what such a registration might include is the
French language or the country of Switzerland (or any other value grandfathered IANA registration "i-enochian". The subtag
in the IANA registry) unless there is a private agreement in 'enochian' could be registered in the IANA registry as a primary
place to do so. See Section 4.5. language subtag (assuming that ISO 639 does not register this
language first), making tags such as "enochian-AQ" and "enochian-
Latn" valid.
7. The single-character subtag 'i' is used by some grandfathered At the time this document was created, there were no examples of
tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other this kind of subtag. Future registrations of this type are
grandfathered tags have a primary language subtag in their first discouraged: an attempt to register any new proposed primary
position.) language MUST be made to the ISO 639 registration authority.
Proposals rejected by the ISO 639 registration authority are
unlikely to meet the criteria for primary language subtags and
are thus unlikely to be registered.
8. Other values MUST NOT be assigned to the primary subtag except by 6. Other values MUST NOT be assigned to the primary subtag except by
revision or update of this document. revision or update of this document.
Note: For languages that have both an ISO 639-1 two-character code When languages have both an ISO 639-1 two-character code and a three-
and an ISO 639-2 three-character code, only the ISO 639-1 two- character code (assigned by ISO 639-2, ISO 639-3, or ISO 639-5), only
character code is defined in the IANA registry. the ISO 639-1 two-character code is defined in the IANA registry.
Note: For languages that have no ISO 639-1 two-character code and for
which the ISO 639-2/T (Terminology) code and the ISO 639-2/B
(Bibliographic) codes differ, only the Terminology code is defined in
the IANA registry. At the time this document was created, all
languages that had both kinds of three-character code were also
assigned a two-character code; it is not expected that future
assignments of this nature will occur.
Note: To avoid problems with versioning and subtag choice as When a language has no ISO 639-1 two-character code and the ISO
experienced during the transition between RFC 1766 and RFC 3066, as 639-2/T (Terminology) code and the ISO 639-2/B (Bibliographic) code
well as the canonical nature of subtags defined by this document, the for that language differ, only the Terminology code is defined in the
ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ IANA registry. At the time this document was created, all languages
RA-JAC) has included the following statement in [iso639.prin]: that had both kinds of three-character codes were also assigned a
two-character code; it is expected that future assignments of this
nature will not occur.
"A language code already in ISO 639-2 at the point of freezing ISO
639-1 shall not later be added to ISO 639-1. This is to ensure
consistency in usage over time, since users are directed in Internet
applications to employ the alpha-3 code when an alpha-2 code for that
language is not available."
In order to avoid instability in the canonical form of tags, if a In order to avoid instability in the canonical form of tags, if a
two-character code is added to ISO 639-1 for a language for which a two-character code is added to ISO 639-1 for a language for which a
three-character code was already included in ISO 639-2, the two- three-character code was already included in either ISO 639-2 or ISO
character code MUST NOT be registered. See Section 3.4. 639-3, the two-character code MUST NOT be registered. See
Section 3.4.
For example, if some content were tagged with 'haw' (Hawaiian), which For example, if some content were tagged with 'haw' (Hawaiian), which
currently has no two-character code, the tag would not be invalidated currently has no two-character code, the tag would not need to be
if ISO 639-1 were to assign a two-character code to the Hawaiian changed if ISO 639-1 were to assign a two-character code to the
language at a later date. Hawaiian language at a later date.
For example, one of the grandfathered IANA registrations is To avoid these problems with versioning and subtag choice (as
"i-enochian". The subtag 'enochian' could be registered in the IANA experienced during the transition between RFC 1766 and RFC 3066), as
registry as a primary language subtag (assuming that ISO 639 does not well as to ensure the canonical nature of subtags defined by this
register this language first), making tags such as "enochian-AQ" and document, the ISO 639 Registration Authority Joint Advisory Committee
"enochian-Latn" valid. (ISO 639/RA-JAC) has included the following statement in
[iso639.prin]:
2.2.2. Extended Language Subtags "A language code already in ISO 639-2 at the point of freezing ISO
639-1 shall not later be added to ISO 639-1. This is to ensure
consistency in usage over time, since users are directed in
Internet applications to employ the alpha-3 code when an alpha-2
code for that language is not available."
The following rules apply to the extended language subtags: 2.2.2. Extended Language Subtags
1. Three-letter subtags immediately following the primary subtag are Extended language subtags are used to identify certain specially
reserved for future standardization, anticipating work that is selected languages that, for various historical and compatibility
currently under way on ISO 639. reasons, are closely identified with or tagged using an existing
primary language subtag. Extended language subtags are always used
with their enclosing primary language subtag (indicated with a
'Prefix' field in the registry) when used to form the language tag.
All languages that have an extended language subtag in the registry
also have an identical primary language subtag record in the
registry. This primary language subtag is RECOMMENDED for forming
the language tag. The following rules apply to the extended language
subtags:
2. Extended language subtags MUST follow the primary subtag and 1. Extended language subtags consist solely of three-letter subtags.
precede any other subtags. All extended language subtag records defined in the registry were
defined according to the assignments found in [ISO639-3].
Language collections and groupings, such as defined in
[ISO639-5], are specifically excluded from being extended
language subtags.
3. There MAY be up to three extended language subtags. 2. Extended language subtag records MUST include exactly one
'Prefix' field indicating an appropriate subtag or sequence of
subtags for that extended language subtag.
4. Extended language subtags MUST NOT be registered or used to form 3. Extended language subtag records MUST include a 'Preferred-
language tags. Their syntax is described here so that Value'. The 'Preferred-Value' and 'Subtag' fields MUST be
implementations can be compatible with any future revision of identical.
this document that does provide for their registration.
Extended language subtag records, once they appear in the registry, 4. Although the ABNF production 'extlang' permits up to three
MUST include exactly one 'Prefix' field indicating an appropriate extended language tags in the language tag, extended language
language subtag or sequence of subtags that MUST always appear as a subtags MUST NOT include another extended language subtag in
prefix to the extended language subtag. their 'Prefix'. That is, the second and third extended language
subtag positions in a language tag are permanently reserved and
tags that include those subtags in that position are, and will
always remain, invalid.
Example: In a future revision or update of this document, the tag For example, the macrolanguage Chinese ('zh') encompasses a number of
"zh-gan" (registered under RFC 3066) might become a valid non- languages. For compatibility reasons, each of these languages has
grandfathered (that is, redundant) tag in which the subtag 'gan' both a primary and extended language subtag in the registry. A few
might represent the Chinese dialect 'Gan'. selected examples of these include Gan Chinese ('gan'), Cantonese
Chinese ('yue'), and Mandarin Chinese ('cmn'). Each is encompassed
by the macrolanguage 'zh' (Chinese). Therefore, they each have the
prefix "zh" in their registry records. Thus, Gan Chinese is
represented with tags beginning "zh-gan" or "gan", Cantonese with
tags beginning either "yue" or "zh-yue", and Mandarin Chinese with
"zh-cmn" or "cmn". The language subtag 'zh' can still be used
without an extended language subtag to label a resource as some
unspecified variety of Chinese, while the primary language subtag
('gan', 'yue', 'cmn') is preferred to using the extended language
form ("zh-gan", "zh-yue", "zh-cmn").
2.2.3. Script Subtag 2.2.3. Script Subtag
Script subtags are used to indicate the script or writing system Script subtags are used to indicate the script or writing system
variations that distinguish the written forms of a language or its variations that distinguish the written forms of a language or its
dialects. The following rules apply to the script subtags: dialects. The following rules apply to the script subtags:
1. All four-character subtags were defined according to 1. Script subtags MUST follow any primary and extended language
[ISO15924]--"Codes for the representation of names of scripts": subtags and MUST precede any other type of subtag.
alpha-4 script codes, or subsequently assigned by the ISO 15924
maintenance agency or governing standardization bodies, denoting
the script or writing system used in conjunction with this
language.
2. Script subtags MUST immediately follow the primary language 2. Script subtags consist of four letters and were defined according
subtag and all extended language subtags and MUST occur before to the assignments found in [ISO15924] ("Information and
any other type of subtag described below. documentation -- Codes for the representation of names of
scripts"), or subsequently assigned by the ISO 15924 registration
authority or governing standardization bodies. Only codes
assigned by ISO 15924 will be considered for registration.
3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private
use in language tags. These subtags correspond to codes reserved use in language tags. These subtags correspond to codes reserved
by ISO 15924 for private use. These codes MAY be used for non- by ISO 15924 for private use. These codes MAY be used for non-
registered script values. Please refer to Section 4.5 for more registered script values. Please refer to Section 4.6 for more
information on private use subtags. information on private use subtags.
4. Script subtags MUST NOT be registered using the process in 4. There MUST be at most one script subtag in a language tag, and
Section 3.5 of this document. Variant subtags MAY be considered
for registration for that purpose.
5. There MUST be at most one script subtag in a language tag, and
the script subtag SHOULD be omitted when it adds no the script subtag SHOULD be omitted when it adds no
distinguishing value to the tag or when the primary language distinguishing value to the tag or when the primary or extended
subtag's record includes a Suppress-Script field listing the language subtag's record in the subtag registry includes a
applicable script subtag. 'Suppress-Script' field listing the applicable script subtag.
Example: "sr-Latn" represents Serbian written using the Latin script. For example: "sr-Latn" represents Serbian written using the Latin
script.
2.2.4. Region Subtag 2.2.4. Region Subtag
Region subtags are used to indicate linguistic variations associated Region subtags are used to indicate linguistic variations associated
with or appropriate to a specific country, territory, or region. with or appropriate to a specific country, territory, or region.
Typically, a region subtag is used to indicate regional dialects or Typically, a region subtag is used to indicate variations such as
usage, or region-specific spelling conventions. A region subtag can regional dialects or usage, or region-specific spelling conventions.
also be used to indicate that content is expressed in a way that is It can also be used to indicate that content is expressed in a way
appropriate for use throughout a region, for instance, Spanish that is appropriate for use throughout a region, for instance,
content tailored to be useful throughout Latin America. Spanish content tailored to be useful throughout Latin America.
The following rules apply to the region subtags: The following rules apply to the region subtags:
1. Region subtags MUST follow any language, extended language, or 1. Region subtags MUST follow any primary language, extended
script subtags and MUST precede all other subtags. language, or script subtags and MUST precede any other type of
subtag.
2. All two-character subtags following the primary subtag were 2. Two-letter region subtags were defined according to the
defined in the IANA registry according to the assignments found assignments found in [ISO3166-1] ("Codes for the representation
in [ISO3166-1] ("Codes for the representation of names of of names of countries and their subdivisions -- Part 1: Country
countries and their subdivisions -- Part 1: Country codes") using codes"), using the list of alpha-2 country codes or using
the list of alpha-2 country codes, or using assignments assignments subsequently made by the ISO 3166-1 maintenance
subsequently made by the ISO 3166 maintenance agency or governing agency or governing standardization bodies. In addition, the
standardization bodies. codes that are "exceptionally reserved" (as opposed to
"assigned") in ISO 3166-1 were also defined in the registry, with
the exception of 'UK', which is an exact synonym for the assigned
code 'GB'.
3. All three-character subtags consisting of digit (numeric) 3. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are
characters following the primary subtag were defined in the IANA reserved for private use in language tags. These subtags
registry according to the assignments found in UN Standard correspond to codes reserved by ISO 3166 for private use. These
Country or Area Codes for Statistical Use [UN_M.49] or codes MAY be used for private use region subtags (instead of
assignments subsequently made by the governing standards body. using a private use subtag sequence). Please refer to
Note that not all of the UN M.49 codes are defined in the IANA Section 4.6 for more information on private use subtags.
registry. The following rules define which codes are entered
into the registry as valid subtags: 4. Three-character region subtags consist solely of digit (number)
characters and were defined according to the assignments found in
the UN Standard Country or Area Codes for Statistical Use
[UN_M.49] or assignments subsequently made by the governing
standards body. Not all of the UN M.49 codes are defined in the
IANA registry. The following rules define which codes are
entered into the registry as valid subtags:
A. UN numeric codes assigned to 'macro-geographical A. UN numeric codes assigned to 'macro-geographical
(continental)' or sub-regions MUST be registered in the (continental)' or sub-regions MUST be registered in the
registry. These codes are not associated with an assigned registry. These codes are not associated with an assigned
ISO 3166 alpha-2 code and represent supra-national areas, ISO 3166-1 alpha-2 code and represent supra-national areas,
usually covering more than one nation, state, province, or usually covering more than one nation, state, province, or
territory. territory.
B. UN numeric codes for 'economic groupings' or 'other B. UN numeric codes for 'economic groupings' or 'other
groupings' MUST NOT be registered in the IANA registry and groupings' MUST NOT be registered in the IANA registry and
MUST NOT be used to form language tags. MUST NOT be used to form language tags.
C. UN numeric codes for countries or areas with ambiguous ISO C. When ISO 3166-1 reassigns a code formerly used for one
3166 alpha-2 codes, when entered into the registry, MUST be country or area to another country or area and that code
defined according to the rules in Section 3.4 and MUST be already is present in the registry, the UN numeric code for
used to form language tags that represent the country or that country or area MUST be registered in the registry as
region for which they are defined. described in Section 3.4 and MUST be used to form language
tags that represent the country or region for which it is
defined (rather than the recycled ISO 3166-1 code).
D. UN numeric codes for countries or areas for which there is an D. UN numeric codes for countries or areas for which there is an
associated ISO 3166 alpha-2 code in the registry MUST NOT be associated ISO 3166-1 alpha-2 code in the registry MUST NOT
entered into the registry and MUST NOT be used to form be entered into the registry and MUST NOT be used to form
language tags. Note that the ISO 3166-based subtag in the language tags. Note that the ISO 3166-based subtag in the
registry MUST actually be associated with the UN M.49 code in registry MUST actually be associated with the UN M.49 code in
question. question.
E. UN numeric codes and ISO 3166 alpha-2 codes for countries or E. For historical reasons, the UN numeric code 830 (Channel
areas listed as eligible for registration in [RFC4645] but Islands), which was not registered at the time this document
not presently registered MAY be entered into the IANA was adopted and had, at that time, no corresponding ISO
registry via the process described in Section 3.5. Once 3166-1 code, MAY be entered into the IANA registry via the
registered, these codes MAY be used to form language tags. process described in Section 3.5, provided no ISO 3166-1 code
with that exact meaning has been previously registered.
F. All other UN numeric codes for countries or areas that do not F. All other UN numeric codes for countries or areas that do not
have an associated ISO 3166 alpha-2 code MUST NOT be entered have an associated ISO 3166-1 alpha-2 code MUST NOT be
into the registry and MUST NOT be used to form language tags. entered into the registry and MUST NOT be used to form
For more information about these codes, see Section 3.4. language tags. For more information about these codes, see
Section 3.4.
4. Note: The alphanumeric codes in Appendix X of the UN document 5. The alphanumeric codes in Appendix X of the UN document MUST NOT
MUST NOT be entered into the registry and MUST NOT be used to be entered into the registry and MUST NOT be used to form
form language tags. (At the time this document was created, language tags. (At the time this document was created, these
these values matched the ISO 3166 alpha-2 codes.) values matched the ISO 3166-1 alpha-2 codes.)
5. There MUST be at most one region subtag in a language tag and the 6. There MUST be at most one region subtag in a language tag and the
region subtag MAY be omitted, as when it adds no distinguishing region subtag MAY be omitted, as when it adds no distinguishing
value to the tag. value to the tag.
6. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are For example:
reserved for private use in language tags. These subtags
correspond to codes reserved by ISO 3166 for private use. These
codes MAY be used for private use region subtags (instead of
using a private use subtag sequence). Please refer to
Section 4.5 for more information on private use subtags.
"de-CH" represents German ('de') as used in Switzerland ('CH'). "de-AT" represents German ('de') as used in Austria ('AT').
"sr-Latn-CS" represents Serbian ('sr') written using Latin script "sr-Latn-RS" represents Serbian ('sr') written using Latin script
('Latn') as used in Serbia and Montenegro ('CS'). ('Latn') as used in Serbia ('RS').
"es-419" represents Spanish ('es') appropriate to the UN-defined "es-419" represents Spanish ('es') appropriate to the UN-defined
Latin America and Caribbean region ('419'). Latin America and Caribbean region ('419').
2.2.5. Variant Subtags 2.2.5. Variant Subtags
Variant subtags are used to indicate additional, well-recognized Variant subtags are used to indicate additional, well-recognized
variations that define a language or its dialects that are not variations that define a language or its dialects that are not
covered by other available subtags. The following rules apply to the covered by other available subtags. The following rules apply to the
variant subtags: variant subtags:
1. Variant subtags are not associated with any external standard. 1. Variant subtags MUST follow any primary language, extended
Variant subtags and their meanings are defined by the language, script, or region subtags and MUST precede any
registration process defined in Section 3.5. extension or private use subtag sequences.
2. Variant subtags MUST follow all of the other defined subtags, but 2. Variant subtags, as a collection, are not associated with any
precede any extension or private use subtag sequences. particular external standard. The meaning of variant subtags in
the registry is defined in the course of the registration process
defined in Section 3.5. Note that any particular variant subtag
might be associated with some external standard. However,
association with a standard is not required for registration.
3. More than one variant MAY be used to form the language tag. 3. More than one variant MAY be used to form the language tag.
4. Variant subtags MUST be registered with IANA according to the 4. Variant subtags MUST be registered with IANA according to the
rules in Section 3.5 of this document before being used to form rules in Section 3.5 of this document before being used to form
language tags. In order to distinguish variants from other types language tags. In order to distinguish variants from other types
of subtags, registrations MUST meet the following length and of subtags, registrations MUST meet the following length and
content restrictions: content restrictions:
1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be
at least five characters long. at least five characters long.
2. Variant subtags that begin with a digit (0-9) MUST be at 2. Variant subtags that begin with a digit (0-9) MUST be at
least four characters long. least four characters long.
Variant subtag records in the language subtag registry MAY include 5. The same variant subtag MUST NOT be used more than once within a
one or more 'Prefix' fields, which indicate the language tag or tags language tag.
that would make a suitable prefix (with other subtags, as
appropriate) in forming a language tag with the variant. For
example, the subtag 'nedis' has a Prefix of "sl", making it suitable
to form language tags such as "sl-nedis" and "sl-IT-nedis", but not
suitable for use in a tag such as "zh-nedis" or "it-IT-nedis".
"sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. * For example, the tag "de-DE-1901-1901" is not valid.
"de-CH-1996" represents German as used in Switzerland and as written Variant subtag records in the Language Subtag Registry MAY include
using the spelling reform beginning in the year 1996 C.E. one or more 'Prefix' (Section 3.1.8) fields. Each 'Prefix' indicates
a suitable sequence of subtags for forming (with other subtags, as
appropriate) a language tag when using the variant.
Most variants that share a prefix are mutually exclusive. For Most variants that share a prefix are mutually exclusive. For
example, the German orthographic variations '1996' and '1901' SHOULD example, the German orthographic variations '1996' and '1901' SHOULD
NOT be used in the same tag, as they represent the dates of different NOT be used in the same tag, as they represent the dates of different
spelling reforms. A variant that can meaningfully be used in spelling reforms. A variant that can meaningfully be used in
combination with another variant SHOULD include a 'Prefix' field in combination with another variant SHOULD include a 'Prefix' field in
its registry record that lists that other variant. For example, if its registry record that lists that other variant. For example, if
another German variant 'example' were created that made sense to use another German variant 'example' were created that made sense to use
with '1996', then 'example' should include two Prefix fields: "de" with '1996', then 'example' should include two 'Prefix' fields: "de"
and "de-1996". and "de-1996".
2.2.6. Extension Subtags For example:
Extensions provide a mechanism for extending language tags for use in "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian.
various applications. See Section 3.7. The following rules apply to
extensions:
1. Extension subtags are separated from the other subtags defined "de-CH-1996" represents German as used in Switzerland and as
in this document by a single-character subtag ("singleton"). written using the spelling reform beginning in the year 1996 C.E.
The singleton MUST be one allocated to a registration authority
via the mechanism described in Section 3.7 and MUST NOT be the
letter 'x', which is reserved for private use subtag sequences.
2. Note: Private use subtag sequences starting with the singleton 2.2.6. Extension Subtags
subtag 'x' are described in Section 2.2.7 below.
3. An extension MUST follow at least a primary language subtag. Extensions provide a mechanism for extending language tags for use in
That is, a language tag cannot begin with an extension. various applications. They are intended to identify information that
Extensions extend language tags, they do not override or replace is commonly used in association with languages or language tags but
them. For example, "a-value" is not a well-formed language tag, that is not part of language identification. See Section 3.7. The
while "de-a-value" is. following rules apply to extensions:
4. Each singleton subtag MUST appear at most one time in each tag 1. An extension MUST follow at least a primary language subtag.
(other than as a private use subtag). That is, singleton That is, a language tag cannot begin with an extension.
subtags MUST NOT be repeated. For example, the tag Extensions extend language tags, they do not override or replace
"en-a-bbb-a-ccc" is invalid because the subtag 'a' appears them. For example, "a-value" is not a well-formed language tag,
twice. Note that the tag "en-a-bbb-x-a-ccc" is valid because while "de-a-value" is. Note that extensions cannot be used in
the second appearance of the singleton 'a' is in a private use tags that are entirely private use (that is, tags starting with
sequence. "x-").
5. Extension subtags MUST meet all of the requirements for the 2. Extension subtags are separated from the other subtags defined in
content and format of subtags defined in this document. this document by a single-character subtag (called a
"singleton"). The singleton MUST be one allocated to a
registration authority via the mechanism described in Section 3.7
and MUST NOT be the letter 'x', which is reserved for private use
subtag sequences.
6. Extension subtags MUST meet whatever requirements are set by the 3. Each singleton subtag MUST appear at most one time in each tag
document that defines their singleton prefix and whatever (other than as a private use subtag). That is, singleton subtags
requirements are provided by the maintaining authority. MUST NOT be repeated. For example, the tag "en-a-bbb-a-ccc" is
invalid because the subtag 'a' appears twice. Note that the tag
"en-a-bbb-x-a-ccc" is valid because the second appearance of the
singleton 'a' is in a private use sequence.
7. Each extension subtag MUST be from two to eight characters long 4. Extension subtags MUST meet whatever requirements are set by the
and consist solely of letters or digits, with each subtag document that defines their singleton prefix and whatever
separated by a single '-'. requirements are provided by the maintaining authority. Note
that there might not be a registry of these subtags and
validating processors are not required to validate extensions.
8. Each singleton MUST be followed by at least one extension 5. Each extension subtag MUST be from two to eight characters long
subtag. For example, the tag "tlh-a-b-foo" is invalid because and consist solely of letters or digits, with each subtag
the first singleton 'a' is followed immediately by another separated by a single '-'. Case distinctions are ignored in
singleton 'b'. extensions (as with any language subtag) and normalized subtags
of this type are expected to be in lowercase.
9. Extension subtags MUST follow all language, extended language, 6. Each singleton MUST be followed by at least one extension subtag.
script, region, and variant subtags in a tag. For example, the tag "tlh-a-b-foo" is invalid because the first
singleton 'a' is followed immediately by another singleton 'b'.
10. All subtags following the singleton and before another singleton 7. Extension subtags MUST follow all primary language, extended
are part of the extension. Example: In the tag "fr-a-Latn", the language, script, region, and variant subtags in a tag and MUST
subtag 'Latn' does not represent the script subtag 'Latn' precede any private use subtag sequences.
defined in the IANA Language Subtag Registry. Its meaning is
defined by the extension 'a'.
11. In the event that more than one extension appears in a single 8. All subtags following the singleton and before another singleton
tag, the tag SHOULD be canonicalized as described in are part of the extension. Example: In the tag "fr-a-Latn", the
Section 4.4. subtag 'Latn' does not represent the script subtag 'Latn' defined
in the IANA Language Subtag Registry. Its meaning is defined by
the extension 'a'.
For example, if the prefix singleton 'r' and the shown subtags were 9. In the event that more than one extension appears in a single
defined, then the following tag would be a valid example: tag, the tag SHOULD be canonicalized as described in Section 4.5,
"en-Latn-GB-boont-r-extended-sequence-x-private". by ordering the various extension sequences into case-insensitive
ASCII order.
For example, if an extension were defined for the singleton 'r' and
it defined the subtags shown, then the following tag would be a valid
example: "en-Latn-GB-boont-r-extended-sequence-x-private".
2.2.7. Private Use Subtags 2.2.7. Private Use Subtags
Private use subtags are used to indicate distinctions in language Private use subtags are used to indicate distinctions in language
important in a given context by private agreement. The following that are important in a given context by private agreement. The
rules apply to private use subtags: following rules apply to private use subtags:
1. Private use subtags are separated from the other subtags defined 1. Private use subtags are separated from the other subtags defined
in this document by the reserved single-character subtag 'x'. in this document by the reserved single-character subtag 'x'.
2. Private use subtags MUST conform to the format and content 2. Private use subtags MUST conform to the format and content
constraints defined in the ABNF for all subtags. constraints defined in the ABNF for all subtags; that is, they
MUST consist solely of letters and digits and not exceed eight
characters in length.
3. Private use subtags MUST follow all language, extended language, 3. Private use subtags MUST follow all primary language, extended
script, region, variant, and extension subtags in the tag. language, script, region, variant, and extension subtags in the
Another way of saying this is that all subtags following the tag. Another way of saying this is that all subtags following
singleton 'x' MUST be considered private use. Example: The the singleton 'x' MUST be considered private use. Example: The
subtag 'US' in the tag "en-x-US" is a private use subtag. subtag 'US' in the tag "en-x-US" is a private use subtag.
4. A tag MAY consist entirely of private use subtags. 4. A tag MAY consist entirely of private use subtags.
5. No source is defined for private use subtags. Use of private use 5. No source is defined for private use subtags. Use of private use
subtags is by private agreement only. subtags is by private agreement only.
6. Private use subtags are NOT RECOMMENDED where alternatives exist 6. Private use subtags are NOT RECOMMENDED where alternatives exist
or for general interchange. See Section 4.5 for more information or for general interchange. See Section 4.6 for more information
on private use subtag choice. on private use subtag choice.
For example: Users who wished to utilize codes from the Ethnologue For example, suppose a group of scholars is studying some texts in
publication of SIL International for language identification might medieval Greek. They might agree to use some collection of private
agree to exchange tags such as "az-Arab-x-AZE-derbend". This example use subtags to identify different styles of writing in the texts.
contains two private use subtags. The first is 'AZE' and the second For example, they might use 'el-x-koine' for documents in the
is 'derbend'. "common" style while using 'el-x-attic' for other documents that
mimic the Attic style. These subtags would not be recognized by
outside processes or systems, but might be useful in categorizing
various texts for study by those in the group.
2.2.8. Preexisting RFC 3066 Registrations In the registry, there are also subtags derived from codes reserved
by ISO 639, ISO 15924, or ISO 3166 for private use. Do not confuse
these with private use subtag sequences following the subtag 'x'.
See Section 4.6.
Existing IANA-registered language tags from RFC 1766 and/or RFC 3066 2.2.8. Grandfathered and Redundant Registrations
maintain their validity. These tags will be maintained in the
registry in records of either the "grandfathered" or "redundant"
type. Grandfathered tags contain one or more subtags that are not
defined in the Language Subtag Registry (see Section 3). Redundant
tags consist entirely of subtags defined above and whose independent
registration is superseded by this document. For more information,
see Section 3.8.
It is important to note that all language tags formed under the Prior to RFC 4646, whole language tags were registered according to
guidelines in this document were either legal, well-formed tags or the rules in RFC 1766 and/or RFC 3066. All of these registered tags
could have been registered under RFC 3066. remain valid as language tags.
Many of these registered tags were made redundant by the advent of
either RFC 4646 or this document. A redundant tag is a grandfathered
registration whose individual subtags appear with the same semantic
meaning in the registry. For example, the tag "zh-Hant" (Traditional
Chinese) can now be composed from the subtags 'zh' (Chinese) and
'Hant' (Han script traditional variant). These redundant tags are
maintained in the registry as records of type 'redundant', mostly as
a matter of historical curiosity.
The remainder of the previously registered tags are "grandfathered".
These tags are classified into two groups: 'regular' and 'irregular'.
Grandfathered tags that (appear to) match the 'langtag' production in
Figure 1 are considered 'regular' grandfathered tags. These tags
contain one or more subtags that either do not individually appear in
the registry or appear but with a different semantic meaning: each
tag, in its entirety, represents a language or collection of
languages.
Grandfathered tags that do not match the 'langtag' production in the
ABNF and would otherwise be invalid are considered 'irregular'
grandfathered tags. With the exception of "en-GB-oed", which is a
variant of "en-GB", each of them, in its entirety, represents a
language.
Many of the grandfathered tags have been superseded by the subsequent
addition of new subtags: each superseded record contains a
'Preferred-Value' field that ought to be used to form language tags
representing that value. For example, the tag "art-lojban" is
superseded by the primary language subtag 'jbo'.
2.2.9. Classes of Conformance 2.2.9. Classes of Conformance
Implementations sometimes need to describe their capabilities with Implementations sometimes need to describe their capabilities with
regard to the rules and practices described in this document. There regard to the rules and practices described in this document. Tags
are two classes of conforming implementations described by this can be checked or verified in a number of ways, but two particular
document: "well-formed" processors and "validating" processors. classes of tag conformance are formally defined here.
Claims of conformance SHOULD explicitly reference one of these
definitions.
An implementation that claims to check for well-formed language tags A tag is considered "well-formed" if it conforms to the ABNF
MUST: (Section 2.1). Language tags may be well-formed in terms of syntax
but not valid in terms of content. However, many operations
involving language tags work well without knowing anything about the
meaning or validity of the subtags.
o Check that the tag and all of its subtags, including extension and A tag is considered "valid" if it satisfies these conditions:
private use subtags, conform to the ABNF or that the tag is on the
list of grandfathered tags.
o Check that singleton subtags that identify extensions do not o The tag is well-formed.
repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not well-
formed.
Well-formed processors are strongly encouraged to implement the o Either the tag is in the list of grandfathered tags or all of its
canonicalization rules contained in Section 4.4. primary language, extended language, script, region, and variant
subtags appear in the IANA Language Subtag Registry as of the
particular registry date.
An implementation that claims to be validating MUST: o There are no duplicate variant subtags.
o Check that the tag is well-formed. o There are no duplicate singleton (extension) subtags.
o Specify the particular registry date for which the implementation Note that a tag's validity depends on the date of the registry used
performs validation of subtags. to validate the tag. A more recent copy of the registry might
contain a subtag that an older version does not.
o Check that either the tag is a grandfathered tag, or that all A tag is considered valid for a given extension (Section 3.7) (as of
language, script, region, and variant subtags consist of valid a particular version, revision, and date) if it meets the criteria
codes for use in language tags according to the IANA registry as for "valid" above and also satisfies this condition:
of the particular date specified by the implementation.
o Specify which, if any, extension RFCs as defined in Section 3.7 Each subtag used in the extension part of the tag is valid
are supported, including version, revision, and date. according to the extension.
o For any such extensions supported, check that all subtags used in Older specifications or language tag implementations sometimes
that extension are valid. reference [RFC3066]. A wider array of tags was considered well-
formed under that document. Any tags that were valid for use under
RFC 3066 are both well-formed and valid under this document's syntax;
only invalid or illegal tags were well-formed under the earlier
definition but no longer are. The language tag syntax under RFC 3066
was:
o For variant and extended language subtags, if the registry obs-language-tag = primary-subtag *( "-" subtag )
contains one or more 'Prefix' fields for that subtag, check that primary-subtag = 1*8ALPHA
the tag matches at least one prefix. The tag matches if all the subtag = 1*8(ALPHA / DIGIT)
subtags in the 'Prefix' also appear in the tag. For example, the
prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both Figure 2: RFC 3066 Language Tag Syntax
the 'es' language subtag and 'CO' region subtag appear in the tag.
Subtags designated for private use as well as private use sequences
introduced by the 'x' subtag are available for cases in which no
assigned subtags are available and registration is not a suitable
option. For example, one might use a tag such as "no-QQ", where 'QQ'
is one of a range of private use ISO 3166-1 codes to indicate an
otherwise undefined region. Users MUST NOT assign language tags that
use subtags that do not appear in the registry other than in private
use sequences (such as the subtag 'personal' in the tag "en-x-
personal"). Besides not being valid, the user also risks collision
with a future possible assignment or registrations.
Note well: although the 'Language-Tag' production appearing in this
document is functionally equivalent to the one in [RFC4646], it has
been changed to prevent certain errors in well-formedness arising
from the old 'grandfathered' production.
3. Registry Format and Maintenance 3. Registry Format and Maintenance
This section defines the Language Subtag Registry and the maintenance The IANA Language Subtag Registry ("the registry") contains a
and update procedures associated with it, as well as a registry for comprehensive list of all of the subtags valid in language tags.
extensions to language tags (Section 3.7). This allows implementers a straightforward and reliable way to
validate language tags. The registry will be maintained so that,
except for extension subtags, it is possible to validate all of the
subtags that appear in a language tag under the provisions of this
document or its revisions or successors. In addition, the meaning of
the various subtags will be unambiguous and stable over time. (The
meaning of private use subtags, of course, is not defined by the
registry.)
The Language Subtag Registry contains a comprehensive list of all of This section defines the registry along with the maintenance and
the subtags valid in language tags. This allows implementers a update procedures associated with it, as well as a registry for
straightforward and reliable way to validate language tags. The extensions to language tags (Section 3.7).
Language Subtag Registry will be maintained so that, except for
extension subtags, it is possible to validate all of the subtags that
appear in a language tag under the provisions of this document or its
revisions or successors. In addition, the meaning of the various
subtags will be unambiguous and stable over time. (The meaning of
private use subtags, of course, is not defined by the IANA registry.)
3.1. Format of the IANA Language Subtag Registry 3.1. Format of the IANA Language Subtag Registry
The IANA Language Subtag Registry ("the registry") consists of a text The IANA Language Subtag Registry is a machine-readable file in the
file that is machine readable in the format described in this format described in this section, plus copies of the registration
section, plus copies of the registration forms approved in accordance forms approved in accordance with the process described in
with the process described in Section 3.5. The existing registration Section 3.5.
forms for grandfathered and redundant tags taken from RFC 3066 will
be maintained as part of the obsolete RFC 3066 registry. The
remaining set of initial subtags will not have registration forms
created for them.
The registry is in the text format described below. This format was The existing registration forms for grandfathered and redundant tags
based on the record-jar format described in [record-jar]. taken from RFC 3066 have been maintained as part of the obsolete RFC
3066 registry. The subtags added to the registry by either [RFC4645]
or [RFC5645] do not have separate registration forms (so no forms are
archived for these additions).
Each line of text is limited to 72 characters, including all 3.1.1. File Format
whitespace. Records are separated by lines containing only the
sequence "%%" (%x25.25).
Each field can be viewed as a single, logical line of ASCII The registry is a [Unicode] text file and consists of a series of
characters, comprising a field-name and a field-body separated by a records in a format based on "record-jar" (described in
COLON character (%x3A). For convenience, the field-body portion of [record-jar]). Each record, in turn, consists of a series of fields
this conceptual entity can be split into a multiple-line that describe the various subtags and tags. The actual registry file
representation; this is called "folding". The format of the registry is encoded using the UTF-8 [RFC3629] character encoding.
is described by the following ABNF (per [RFC4234]):
Each field can be considered a single, logical line of characters.
Each field contains a "field-name" and a "field-body". These are
separated by a "field-separator". The field-separator is a COLON
character (U+003A) plus any surrounding whitespace. Each field is
terminated by the newline sequence CRLF. The text in each field MUST
be in Unicode Normalization Form C (NFC).
A collection of fields forms a "record". Records are separated by
lines containing only the sequence "%%" (U+0025 U+0025).
Although fields are logically a single line of text, each line of
text in the file format is limited to 72 bytes in length. To
accommodate this, the field-body can be split into a multiple-line
representation; this is called "folding". Folding is done according
to customary conventions for line-wrapping. This is typically on
whitespace boundaries, but can occur between other characters when
the value does not include spaces, such as when a language does not
use whitespace between words. In any event, there MUST NOT be breaks
inside a multibyte UTF-8 sequence or in the middle of a combining
character sequence. For more information, see [UAX14].
Although the file format uses the Unicode character set and the file
itself is encoded using the UTF-8 encoding, fields are restricted to
the printable characters from the US-ASCII [ISO646] repertoire unless
otherwise indicated in the description of a specific field
(Section 3.1.2).
The format of the registry is described by the following ABNF
[RFC5234]. Character numbers (code points) are taken from Unicode,
and terminals in the ABNF productions are in terms of characters
rather than bytes.
registry = record *("%%" CRLF record) registry = record *("%%" CRLF record)
record = 1*( field-name *SP ":" *SP field-body CRLF ) record = 1*field
field = ( field-name field-sep field-body CRLF )
field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)] field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)]
field-body = *(ASCCHAR/LWSP) field-sep = *SP ":" *SP
ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26 field-body = *([[*SP CRLF] 1*SP] 1*CHARS)
UNICHAR = "&#x" 2*6HEXDIG ";" CHARS = (%x21-10FFFF) ; Unicode code points
Figure 2: Registry Format ABNF Figure 3: Registry Format ABNF
The sequence '..' (%x2E.2E) in a field-body denotes a range of The sequence '..' (U+002E U+002E) in a field-body denotes a range of
values. Such a range represents all subtags of the same length that values. Such a range represents all subtags of the same length that
are in alphabetic or numeric order within that range, including the are in alphabetic or numeric order within that range, including the
values explicitly mentioned. For example 'a..c' denotes the values values explicitly mentioned. For example, 'a..c' denotes the values
'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and 'a', 'b', and 'c', and '11..13' denotes the values '11', '12', and
'13'. '13'.
Characters from outside the US-ASCII [ISO646] repertoire, as well as
the AMPERSAND character ("&", %x26) when it occurs in a field-body,
are represented by a "Numeric Character Reference" using hexadecimal
notation in the style used by [XML10] (see
<http://www.w3.org/TR/REC-xml/#dt-charref>). This consists of the
sequence "&#x" (%x26.23.78) followed by a hexadecimal representation
of the character's code point in [ISO10646] followed by a closing
semicolon (%x3B). For example, the EURO SIGN, U+20AC, would be
represented by the sequence "&#x20AC;". Note that the hexadecimal
notation MAY have between two and six digits.
All fields whose field-body contains a date value use the "full-date" All fields whose field-body contains a date value use the "full-date"
format specified in [RFC3339]. For example: "2004-06-28" represents format specified in [RFC3339]. For example, "2004-06-28" represents
June 28, 2004, in the Gregorian calendar. June 28, 2004, in the Gregorian calendar.
The first record in the file contains the single field whose field- 3.1.2. Record and Field Definitions
name is "File-Date" (see Figure 3). The field-body of this record
contains the last modification date of this copy of the registry, There are three types of records in the registry: "File-Date",
making it possible to compare different versions of the registry. "Subtag", and "Tag".
The registry on the IANA website is the most current. Versions with
an older date than that one are not up-to-date. The first record in the registry is always the "File-Date" record.
This record occurs only once in the file and contains a single field
whose field-name is "File-Date". The field-body of this record
contains a date (see Section 5.1), making it possible to easily
recognize different versions of the registry.
File-Date: 2004-06-28 File-Date: 2004-06-28
%% %%
Figure 3: Example of the File-Date Record Figure 4: Example of the File-Date Record
Subsequent records represent subtags in the registry. Each of the Subsequent records contain multiple fields and represent information
fields in each record MUST occur no more than once, unless otherwise about either subtags or tags. Both types of records have an
noted below. Each record MUST contain the following fields: identical structure, except that "Subtag" records contain a field
with a field-name of "Subtag", while, unsurprisingly, "Tag" records
contain a field with a field-name of "Tag". Field-names MUST NOT
occur more than once per record, with the exception of the
'Description', 'Comments', and 'Prefix' fields.
Each record MUST contain at least one of each of the following
fields:
o 'Type' o 'Type'
* Type's field-value MUST consist of one of the following * Type's field-body MUST consist of one of the following strings:
strings: "language", "extlang", "script", "region", "variant", "language", "extlang", "script", "region", "variant",
"grandfathered", and "redundant" and denotes the type of tag or "grandfathered", and "redundant"; it denotes the type of tag or
subtag. subtag.
o Either 'Subtag' or 'Tag' o Either 'Subtag' or 'Tag'
* Subtag's field-value contains the subtag being defined. This * Subtag's field-body contains the subtag being defined. This
field MUST only appear in records of whose 'Type' has one of field MUST appear in all records whose 'Type' has one of these
these values: "language", "extlang", "script", "region", or values: "language", "extlang", "script", "region", or
"variant". "variant".
* Tag's field-value contains a complete language tag. This field * Tag's field-body contains a complete language tag. This field
MUST only appear in records whose 'Type' has one of these MUST appear in all records whose 'Type' has one of these
values: "grandfathered" or "redundant". Note that the field- values: "grandfathered" or "redundant". If the 'Type' is
value will always follow the 'grandfathered' production in the "grandfathered", then the 'Tag' field-body will be one of the
ABNF in Section 2.1 tags listed in either the 'regular' or 'irregular' production
found in Section 2.1.
o Description o 'Description'
* Description's field-value contains a non-normative description * Description's field-body contains a non-normative description
of the subtag or tag. of the subtag or tag.
o Added o 'Added'
* Added's field-value contains the date the record was added to * Added's field-body contains the date the record was registered
the registry. or, in the case of grandfathered or redundant tags, the date
the corresponding tag was registered under the rules of
[RFC1766] or [RFC3066].
The 'Subtag' or 'Tag' field MUST use lowercase letters to form the Each record MAY also contain the following fields:
subtag or tag, with two exceptions. Subtags whose 'Type' field is
'script' (in other words, subtags defined by ISO 15924) MUST use
titlecase. Subtags whose 'Type' field is 'region' (in other words,
subtags defined by ISO 3166) MUST use uppercase. These exceptions
mirror the use of case in the underlying standards.
The field 'Description' MAY appear more than one time and contains a o 'Deprecated'
description of the tag or subtag in the record. At least one of the
'Description' fields MUST be written or transcribed into the Latin
script; the same or additional fields MAY also include a description
in a non-Latin script. The 'Description' field is used for
identification purposes and SHOULD NOT be taken to represent the
actual native name of the language or variation or to be in any
particular language. Most descriptions are taken directly from
source standards such as ISO 639 or ISO 3166.
Note: Descriptions in registry entries that correspond to ISO 639, * Deprecated's field-body contains the date the record was
ISO 15924, ISO 3166, or UN M.49 codes are intended only to indicate deprecated. In some cases, this value is earlier than that of
the meaning of that identifier as defined in the source standard at the 'Added' field in the same record. That is, the date of
the time it was added to the registry. The description does not deprecation preceded the addition of the record to the
replace the content of the source standard itself. The descriptions registry.
are not intended to be the English localized names for the subtags.
Localization or translation of language tag and subtag descriptions
is out of scope of this document.
Each record MAY also contain the following fields: o 'Preferred-Value'
o Preferred-Value * Preferred-Value's field-body contains a canonical mapping from
this record's value to a modern equivalent that is preferred in
its place. Depending on the value of the 'Type' field, this
value can take different forms:
* For fields of type 'language', 'extlang', 'script', 'region', + For fields of type 'language', 'Preferred-Value' contains
and 'variant', 'Preferred-Value' contains the subtag of the the primary language subtag that is preferred when forming
same 'Type' that is preferred for forming the language tag. the language tag.
* For fields of type 'grandfathered' and 'redundant', a canonical + For fields of type 'script', 'region', or 'variant',
mapping to a complete language tag. 'Preferred-Value' contains the subtag of the same type that
is preferred for forming the language tag.
o Deprecated + For fields of type 'extlang', 'grandfathered', or
'redundant', 'Preferred-Value' contains an "extended
language range" [RFC4647] that is preferred for forming the
language tag. That is, the preferred language tag will
contain, in order, each of the subtags that appears in the
'Preferred-Value'; additional fields can be included in a
language tag, as described elsewhere in this document. For
example, the replacement for the grandfathered tag "zh-min-
nan" (Min Nan Chinese) is "nan", which can be used as the
basis for tags such as "nan-Hant" or "nan-TW" (note that the
extended language subtag form such as "zh-nan-Hant" or "zh-
nan-TW" can also be used).
* Deprecated's field-value contains the date the record was o 'Prefix'
deprecated.
o Prefix * Prefix's field-body contains a valid language tag that is
RECOMMENDED as one possible prefix to this record's subtag.
This field MAY appear in records whose 'Type' field-body is
either 'extlang' or 'variant' (it MUST NOT appear in any other
record type).
* Prefix's field-value contains a language tag with which this o 'Suppress-Script'
subtag MAY be used to form a new language tag, perhaps with
other subtags as well. This field MUST only appear in records
whose 'Type' field-value is 'variant' or 'extlang'. For
example, the 'Prefix' for the variant 'nedis' is 'sl', meaning
that the tags "sl-nedis" and "sl-IT-nedis" might be appropriate
while the tag "is-nedis" is not.
o Comments * Suppress-Script's field-body contains a script subtag that
SHOULD NOT be used to form language tags with the associated
primary or extended language subtag. This field MUST appear
only in records whose 'Type' field-body is 'language' or
'extlang'. See Section 4.1.
* Comments contains additional information about the subtag, as o 'Macrolanguage'
deemed appropriate for understanding the registry and
implementing language tags using the subtag or tag.
o Suppress-Script * Macrolanguage's field-body contains a primary language subtag
defined by ISO 639 as the "macrolanguage" that encompasses this
language subtag. This field MUST appear only in records whose
'Type' field-body is either 'language' or 'extlang'.
* Suppress-Script contains a script subtag that SHOULD NOT be o 'Scope'
used to form language tags with the associated primary language
subtag. This field MUST only appear in records whose 'Type'
field-value is 'language'. See Section 4.1.
The field 'Deprecated' MAY be added to any record via the maintenance * Scope's field-body contains information about a primary or
process described in Section 3.3 or via the registration process extended language subtag indicating the type of language code
described in Section 3.5. Usually, the addition of a 'Deprecated' according to ISO 639. The values permitted in this field are
field is due to the action of one of the standards bodies, such as "macrolanguage", "collection", "special", and "private-use".
ISO 3166, withdrawing a code. In some historical cases, it might not This field only appears in records whose 'Type' field-body is
have been possible to reconstruct the original deprecation date. For either 'language' or 'extlang'. When this field is omitted,
these cases, an approximate date appears in the registry. Although the language is an individual language.
valid in language tags, subtags and tags with a 'Deprecated' field
are deprecated and validating processors SHOULD NOT generate these o 'Comments'
* Comments's field-body contains additional information about the
subtag, as deemed appropriate for understanding the registry
and implementing language tags using the subtag or tag.
Future versions of this document might add additional fields to the
registry; implementations SHOULD ignore fields found in the registry
that are not defined in this document.
3.1.3. Type Field
The field 'Type' contains the string identifying the record type in
which it appears. Values for the 'Type' field-body are: "language"
(Section 2.2.1); "extlang" (Section 2.2.2); "script" (Section 2.2.3);
"region" (Section 2.2.4); "variant" (Section 2.2.5); "grandfathered"
or "redundant" (Section 2.2.8).
3.1.4. Subtag and Tag Fields
The field 'Subtag' contains the subtag defined in the record. The
field 'Tag' appears in records whose 'Type' is either 'grandfathered'
or 'redundant' and contains a tag registered under [RFC3066].
The 'Subtag' field-body MUST follow the casing conventions described
in Section 2.1.1. All subtags use lowercase letters in the field-
body, with two exceptions:
Subtags whose 'Type' field is 'script' (in other words, subtags
defined by ISO 15924) MUST use titlecase.
Subtags whose 'Type' field is 'region' (in other words, the non-
numeric region subtags defined by ISO 3166-1) MUST use all
uppercase.
The 'Tag' field-body MUST be formatted according to the rules
described in Section 2.1.1.
3.1.5. Description Field
The field 'Description' contains a description of the tag or subtag
in the record. The 'Description' field MAY appear more than once per
record. The 'Description' field MAY include the full range of
Unicode characters. At least one of the 'Description' fields MUST be
written or transcribed into the Latin script; additional
'Description' fields MAY be in any script or language.
The 'Description' field is used for identification purposes.
Descriptions SHOULD contain all and only that information necessary
to distinguish one subtag from others with which it might be
confused. They are not intended to provide general background
information or to provide all possible alternate names or
designations. 'Description' fields don't necessarily represent the
actual native name of the item in the record, nor are any of the
descriptions guaranteed to be in any particular language (such as
English or French, for example).
Descriptions in the registry that correspond to ISO 639, ISO 15924,
ISO 3166-1, or UN M.49 codes are intended only to indicate the
meaning of that identifier as defined in the source standard at the
time it was added to the registry or as subsequently modified, within
the bounds of the stability rules (Section 3.4), via subsequent
registration. The 'Description' does not replace the content of the
source standard itself. 'Description' fields are not intended to be
the localized English names for the subtags. Localization or
translation of language tag and subtag descriptions is out of scope
of this document.
For subtags taken from a source standard (such as ISO 639 or ISO
15924), the 'Description' fields in the record are also initially
taken from that source standard. Multiple descriptions in the source
standard are split into separate 'Description' fields. The source
standard's descriptions MAY be edited or modified, either prior to
insertion or via the registration process, and additional or
extraneous descriptions omitted or removed. Each 'Description' field
MUST be unique within the record in which it appears, and formatting
variations of the same description SHOULD NOT occur in that specific
record. For example, while the ISO 639-1 code 'fy' has both the
description "Western Frisian" and the description "Frisian, Western"
in that standard, only one of these descriptions appears in the
registry.
To help ensure that users do not become confused about which subtag
to use, 'Description' fields assigned to a record of any specific
type ('language', 'extlang', 'script', and so on) MUST be unique
within that given record type with the following exception: if a
particular 'Description' field occurs in multiple records of a given
type, then at most one of the records can omit the 'Deprecated'
field. All deprecated records that share a 'Description' MUST have
the same 'Preferred-Value', and all non-deprecated records MUST be
that 'Preferred-Value'. This means that two records of the same type
that share a 'Description' are also semantically equivalent and no
more than one record with a given 'Description' is preferred for that
meaning.
For example, consider the 'language' subtags 'zza' (Zaza) and 'diq'
(Dimli). It so happens that 'zza' is a macrolanguage enclosing 'diq'
and thus also has a description in ISO 639-3 of "Dimli". This
description was edited to read "Dimli (macrolanguage)" in the
registry record for 'zza' to prevent a collision.
By contrast, the subtags 'he' and 'iw' share a 'Description' value of
"Hebrew"; this is permitted because 'iw' is deprecated and its
'Preferred-Value' is 'he'.
For fields of type 'language', the first 'Description' field
appearing in the registry corresponds whenever possible to the
Reference Name assigned by ISO 639-3. This helps facilitate cross-
referencing between ISO 639 and the registry.
When creating or updating a record due to the action of one of the
source standards, the Language Subtag Reviewer MAY edit descriptions
to correct irregularities in formatting (such as misspellings,
inappropriate apostrophes or other punctuation, or excessive or
missing spaces) prior to submitting the proposed record to the
ietf-languages@iana.org list for consideration.
3.1.6. Deprecated Field
The field 'Deprecated' contains the date the record was deprecated
and MAY be added, changed, or removed from any record via the
maintenance process described in Section 3.3 or via the registration
process described in Section 3.5. Usually, the addition of a
'Deprecated' field is due to the action of one of the standards
bodies, such as ISO 3166, withdrawing a code. Although valid in
language tags, subtags and tags with a 'Deprecated' field are
deprecated, and validating processors SHOULD NOT generate these
subtags. Note that a record that contains a 'Deprecated' field and subtags. Note that a record that contains a 'Deprecated' field and
no corresponding 'Preferred-Value' field has no replacement mapping. no corresponding 'Preferred-Value' field has no replacement mapping.
In some historical cases, it might not have been possible to
reconstruct the original deprecation date. For these cases, an
approximate date appears in the registry. Some subtags and some
grandfathered or redundant tags were deprecated before the initial
creation of the registry. The exact rules for this appear in Section
2 of [RFC4645]. Note that these records have a 'Deprecated' field
with an earlier date then the corresponding 'Added' field!
3.1.7. Preferred-Value Field
The field 'Preferred-Value' contains a mapping between the record in The field 'Preferred-Value' contains a mapping between the record in
which it appears and another tag or subtag. The value in this field which it appears and another tag or subtag (depending on the record's
is STRONGLY RECOMMENDED as the best choice to represent the value of 'Type'). The value in this field is used for canonicalization (see
this record when selecting a language tag. These values form three Section 4.5). In cases where the subtag or tag also has a
'Deprecated' field, then the 'Preferred-Value' is RECOMMENDED as the
best choice to represent the value of this record when selecting a
language tag.
Records containing a 'Preferred-Value' fall into one of these four
groups: groups:
1. ISO 639 language codes that were later withdrawn in favor of 1. ISO 639 language codes that were later withdrawn in favor of
other codes. These values are mostly a historical curiosity. other codes. These values are mostly a historical curiosity.
The 'he'/'iw' pairing above is an example of this.
2. ISO 3166 region codes that have been withdrawn in favor of a new 2. Subtags (with types other than language or extlang) taken from
code. This sometimes happens when a country changes its name or codes or values that have been withdrawn in favor of a new code.
administration in such a way that warrants a new region code. In particular, this applies to region subtags taken from ISO
3166-1, because sometimes a country will change its name or
administration in such a way that warrants a new region code. In
some cases, countries have reverted to an older name, which might
already be encoded. For example, the subtag 'ZR' (Zaire) was
replaced by the subtag 'CD' (Democratic Republic of the Congo)
when that country's name was changed.
3. Tags grandfathered from RFC 3066. In many cases, these tags have 3. Tags or subtags that have become obsolete because the values they
become obsolete because the values they represent were later represent were later encoded. Many of the grandfathered or
encoded by ISO 639. redundant tags were later encoded by ISO 639, for example, and
fall into this grouping. For example, "i-klingon" was deprecated
when the subtag 'tlh' was added. The record for "i-klingon" has
a 'Preferred-Value' of 'tlh'.
Records that contain a 'Preferred-Value' field MUST also have a 4. Extended language subtags always have a mapping to their
'Deprecated' field. This field contains a date of deprecation. identical primary language subtag. For example, the extended
Thus, a language tag processor can use the registry to construct the language subtag 'yue' (Cantonese) can be used to form the tag
valid, non-deprecated set of subtags for a given date. In addition, "zh-yue". It has a 'Preferred-Value' mapping to the primary
for any given tag, a processor can construct the set of valid language subtag 'yue', meaning that a tag such as
language tags that correspond to that tag for all dates up to the "zh-yue-Hant-HK" can be canonicalized to "yue-Hant-HK".
date of the registry. The ability to do these mappings MAY be
beneficial to applications that are matching, selecting, for
filtering content based on its language tags.
Note that 'Preferred-Value' mappings in records of type 'region' Records other than those of type 'extlang' that contain a 'Preferred-
sometimes do not represent exactly the same meaning as the original Value' field MUST also have a 'Deprecated' field. This field
value. There are many reasons for a country code to be changed, and contains the date on which the tag or subtag was deprecated in favor
the effect this has on the formation of language tags will depend on of the preferred value.
the nature of the change in question.
In particular, the 'Preferred-Value' field does not imply retagging For records of type 'extlang', the 'Preferred-Value' field appears
content that uses the affected subtag. without a corresponding 'Deprecated' field. An implementation MAY
ignore these preferred value mappings, although if it ignores the
mapping, it SHOULD do so consistently. It SHOULD also treat the
'Preferred-Value' as equivalent to the mapped item. For example, the
tags "zh-yue-Hant-HK" and "yue-Hant-HK" are semantically equivalent
and ought to be treated as if they were the same tag.
The field 'Preferred-Value' MUST NOT be modified once created in the Occasionally, the deprecated code is preferred in certain contexts.
registry. The field MAY be added to records of type "grandfathered" For example, both "iw" and "he" can be used in the Java programming
and "region" according to the rules in Section 3.3. Otherwise the language, but "he" is converted on input to "iw", which is thus the
field MUST NOT be added to any record already in the registry. canonical form in Java.
The 'Preferred-Value' field in records of type "grandfathered" and 'Preferred-Value' mappings in records of type 'region' sometimes do
"redundant" contains whole language tags that are strongly not represent exactly the same meaning as the original value. There
RECOMMENDED for use in place of the record's value. In many cases, are many reasons for a country code to be changed, and the effect
the mappings were created by deprecation of the tags during the this has on the formation of language tags will depend on the nature
period before this document was adopted. For example, the tag of the change in question. For example, the region subtag 'YD'
(Democratic Yemen) was deprecated in favor of the subtag 'YE' (Yemen)
when those two countries unified in 1990.
A 'Preferred-Value' MAY be added to, changed, or removed from records
according to the rules in Section 3.3. Addition, modification, or
removal of a 'Preferred-Value' field in a record does not imply that
content using the affected subtag needs to be retagged.
The 'Preferred-Value' fields in records of type "grandfathered" and
"redundant" each contain an "extended language range" [RFC4647] that
is strongly RECOMMENDED for use in place of the record's value. In
many cases, these mappings were created via deprecation of the tags
during the period before [RFC4646] was adopted. For example, the tag
"no-nyn" was deprecated in favor of the ISO 639-1-defined language "no-nyn" was deprecated in favor of the ISO 639-1-defined language
code 'nn'. code 'nn'.
Records of type 'variant' MAY have more than one field of type The 'Preferred-Value' field in subtag records of type "extlang" also
'Prefix'. Additional fields of this type MAY be added to a 'variant' contains an "extended language range". This allows the subtag to be
record via the registration process. deprecated in favor of either a single primary language subtag or a
new language-extlang sequence.
Records of type 'extlang' MUST have _exactly_ one 'Prefix' field. Usually, the addition, removal, or change of a 'Preferred-Value'
field for a subtag is done to reflect changes in one of the source
standards. For example, if an ISO 3166-1 region code is deprecated
in favor of another code, that SHOULD result in the addition of a
'Preferred-Value' field.
The field-value of the 'Prefix' field consists of a language tag Changes to one subtag can affect other subtags as well: when
whose subtags are appropriate to use with this subtag. For example, proposing changes to the registry, the Language Subtag Reviewer MUST
the variant subtag '1996' has a 'Prefix' field of "de". This means review the registry for such effects and propose the necessary
that tags starting with the sequence "de-" are appropriate with this changes using the process in Section 3.5, although anyone MAY request
subtag, so "de-Latg-1996" and "de-CH-1996" are both acceptable, while such changes. For example:
the tag "fr-1996" is an inappropriate choice.
The field of type 'Prefix' MUST NOT be removed from any record. The Suppose that subtag 'XX' has a 'Preferred-Value' of 'YY'. If 'YY'
field-value for this type of field MUST NOT be modified. later changes to have a 'Preferred-Value' of 'ZZ', then the
'Preferred-Value' for 'XX' MUST also change to be 'ZZ'.
The field 'Comments' MAY appear more than once per record. This Suppose that a registered language subtag 'dialect' represents a
field MAY be inserted or changed via the registration process and no language not yet available in any part of ISO 639. The later
guarantee of stability is provided. The content of this field is not addition of a corresponding language code in ISO 639 SHOULD result
restricted, except by the need to register the information, the in the addition of a 'Preferred-Value' for 'dialect'.
suitability of the request, and by reasonable practical size
limitations.
The field 'Suppress-Script' MUST only appear in records whose 'Type' 3.1.8. Prefix Field
field-value is 'language'. This field MUST NOT appear more than one
time in a record. This field indicates a script used to write the
overwhelming majority of documents for the given language and that
therefore adds no distinguishing information to a language tag. It
helps ensure greater compatibility between the language tags
generated according to the rules in this document and language tags
and tag processors or consumers based on RFC 3066. For example,
virtually all Icelandic documents are written in the Latin script,
making the subtag 'Latn' redundant in the tag "is-Latn".
3.2. Language Subtag Reviewer The field 'Prefix' contains a valid language tag that is RECOMMENDED
as one possible prefix to this record's subtag, perhaps with other
subtags. That is, when including an extended language or a variant
subtag that has at least one 'Prefix' in a language tag, the
resulting tag SHOULD match at least one of the subtag's 'Prefix'
fields using the "Extended Filtering" algorithm (see [RFC4647]), and
each of the subtags in that 'Prefix' SHOULD appear before the subtag
itself.
The Language Subtag Reviewer is appointed by the IESG for an The 'Prefix' field MUST appear exactly once in a record of type
indefinite term, subject to removal or replacement at the IESG's 'extlang'. The 'Prefix' field MAY appear multiple times (or not at
discretion. The Language Subtag Reviewer moderates the ietf- all) in records of type 'variant'. Additional fields of this type
languages mailing list, responds to requests for registration, and MAY be added to a 'variant' record via the registration process,
performs the other registry maintenance duties described in provided the 'variant' record already has at least one 'Prefix'
Section 3.3. Only the Language Subtag Reviewer is permitted to field.
request IANA to change, update, or add records to the Language Subtag
Registry.
The performance or decisions of the Language Subtag Reviewer MAY be Each 'Prefix' field indicates a particular sequence of subtags that
appealed to the IESG under the same rules as other IETF decisions form a meaningful tag with this subtag. For example, the extended
(see [RFC2026]). The IESG can reverse or overturn the decision of language subtag 'cmn' (Mandarin Chinese) only makes sense with its
the Language Subtag Reviewer, provide guidance, or take other prefix 'zh' (Chinese). Similarly, 'rozaj' (Resian, a dialect of
appropriate actions. Slovenian) would be appropriate when used with its prefix 'sl'
(Slovenian), while tags such as "is-1994" are not appropriate (and
probably not meaningful). Although the 'Prefix' for 'rozaj' is "sl",
other subtags might appear between them. For example, the tag "sl-
IT-rozaj" (Slovenian, Italy, Resian) matches the 'Prefix' "sl".
3.3. Maintenance of the Registry The 'Prefix' also indicates when variant subtags make sense when used
together (many that otherwise share a 'Prefix' are mutually
exclusive) and what the relative ordering of variants is supposed to
be. For example, the variant '1994' (Standardized Resian
orthography) has several 'Prefix' fields in the registry ("sl-rozaj",
"sl-rozaj-biske", "sl-rozaj-njiva", "sl-rozaj-osojs", and "sl-rozaj-
solba"). This indicates not only that '1994' is appropriate to use
with each of these five Resian variant subtags ('rozaj', 'biske',
'njiva', 'osojs', and 'solba'), but also that it SHOULD appear
following any of these variants in a tag. Thus, the language tag
ought to take the form "sl-rozaj-biske-1994", rather than "sl-1994-
rozaj-biske" or "sl-rozaj-1994-biske".
Maintenance of the registry requires that as codes are assigned or If a record includes no 'Prefix' field, a 'Prefix' field MUST NOT be
withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language added to the record at a later date. Otherwise, changes (additions,
Subtag Reviewer MUST evaluate each change, determine whether it deletions, or modifications) to the set of 'Prefix' fields MAY be
conflicts with existing registry entries, and submit the information registered, as long as they strictly widen the range of language tags
to IANA for inclusion in the registry. If a change takes place and that are recommended. For example, a 'Prefix' with the value "be-
the Language Subtag Reviewer does not do this in a timely manner, Latn" (Belarusian, Latin script) could be replaced by the value "be"
then any interested party MAY use the procedure in Section 3.5 to (Belarusian) but not by the value "ru-Latn" (Russian, Latin script)
register the appropriate update. or the value "be-Latn-BY" (Belarusian, Latin script, Belarus), since
these latter either change or narrow the range of suggested tags.
Note: The redundant and grandfathered entries together are the The field-body of the 'Prefix' field MUST NOT conflict with any
complete list of tags registered under [RFC3066]. The redundant tags 'Prefix' already registered for a given record. Such a conflict
are those that can now be formed using the subtags defined in the would occur when no valid tag could be constructed that would contain
registry together with the rules of Section 2.2. The grandfathered the prefix, such as when two subtags each have a 'Prefix' that
entries include those that can never be legal under those same contains the other subtag. For example, suppose that the subtag
provisions. 'avariant' has the prefix "es-bvariant". Then the subtag 'bvariant'
cannot be assigned the prefix 'avariant', for that would require a
tag of the form "es-avariant-bvariant-avariant", which would not be
valid.
The set of redundant and grandfathered tags is permanent and stable: 3.1.9. Suppress-Script Field
new entries in this section MUST NOT be added and existing entries
MUST NOT be removed. Records of type 'grandfathered' MAY have their
type converted to 'redundant'; see item 12 in Section 3.6 for more
information. The decision-making process about which tags were
initially grandfathered and which were made redundant is described in
[RFC4645].
RFC 3066 tags that were deprecated prior to the adoption of this The field 'Suppress-Script' contains a script subtag (whose record
document are part of the list of grandfathered tags, and their appears in the registry). The field 'Suppress-Script' MUST appear
component subtags were not included as registered variants (although only in records whose 'Type' field-body is either 'language' or
they remain eligible for registration). For example, the tag 'extlang'. This field MUST NOT appear more than one time in a
"art-lojban" was deprecated in favor of the language subtag 'jbo'. record.
The Language Subtag Reviewer MUST ensure that new subtags meet the This field indicates a script used to write the overwhelming majority
requirements in Section 4.1 or submit an appropriate alternate subtag of documents for the given language. The subtag for such a script
as described in that section. When either a change or addition to therefore adds no distinguishing information to a language tag and
the registry is needed, the Language Subtag Reviewer MUST prepare the thus SHOULD NOT be used for most documents in that language.
complete record, including all fields, and forward it to IANA for Omitting the script subtag indicated by this field helps ensure
insertion into the registry. Each record being modified or inserted greater compatibility between the language tags generated according
MUST be forwarded in a separate message. to the rules in this document and language tags and tag processors or
consumers based on RFC 3066. For example, virtually all Icelandic
documents are written in the Latin script, making the subtag 'Latn'
redundant in the tag "is-Latn".
If a record represents a new subtag that does not currently exist in Many language subtag records do not have a 'Suppress-Script' field.
the registry, then the message's subject line MUST include the word The lack of a 'Suppress-Script' might indicate that the language is
"INSERT". If the record represents a change to an existing subtag, customarily written in more than one script or that the language is
then the subject line of the message MUST include the word "MODIFY". not customarily written at all. It might also mean that sufficient
The message MUST contain both the record for the subtag being information was not available when the record was created and thus
inserted or modified and the new File-Date record. Here is an remains a candidate for future registration.
example of what the body of the message might contain:
LANGUAGE SUBTAG MODIFICATION 3.1.10. Macrolanguage Field
File-Date: 2005-01-02
%%
Type: variant
Subtag: nedis
Description: Natisone dialect
Description: Nadiza dialect
Added: 2003-10-09
Prefix: sl
Comments: This is a comment shown
as an example.
%%
Figure 4: Example of a Language Subtag Modification Form The field 'Macrolanguage' contains a primary language subtag (whose
record appears in the registry). This field indicates a language
that encompasses this subtag's language according to assignments made
by ISO 639-3.
Whenever an entry is created or modified in the registry, the ISO 639-3 labels some languages in the registry as "macrolanguages".
'File-Date' record at the start of the registry is updated to reflect ISO 639-3 defines the term "macrolanguage" to mean "clusters of
the most recent modification date in the [RFC3339] "full-date" closely-related language varieties that [...] can be considered
format. distinct individual languages, yet in certain usage contexts a single
language identity for all is needed". These correspond to codes
registered in ISO 639-2 as individual languages that were found to
correspond to more than one language in ISO 639-3.
Before forwarding a new registration to IANA, the Language Subtag A language contained within a macrolanguage is called an "encompassed
Reviewer MUST ensure that values in the 'Subtag' field match case language". The record for each encompassed language contains a
according to the description in Section 3.1. 'Macrolanguage' field in the registry; the macrolanguages themselves
are not specially marked. Note that some encompassed languages have
ISO 639-1 or ISO 639-2 codes.
The 'Macrolanguage' field can only occur in records of type
'language' or 'extlang'. Only values assigned by ISO 639-3 will be
considered for inclusion. 'Macrolanguage' fields MAY be added or
removed via the normal registration process whenever ISO 639-3
defines new values or withdraws old values. Macrolanguages are
informational, and MAY be removed or changed if ISO 639-3 changes the
values. For more information on the use of this field and choosing
between macrolanguage and encompassed language subtags, see
Section 4.1.1.
For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn'
(Norwegian Nynorsk) each have a 'Macrolanguage' field with a value of
'no' (Norwegian). For more information, see Section 4.1.
3.1.11. Scope Field
The field 'Scope' contains classification information about a primary
or extended language subtag derived from ISO 639. Most languages
have a scope of 'individual', which means that the language is not a
macrolanguage, collection, special code, or private use. That is, it
is what one would normally consider to be 'a language'. Any primary
or extended language subtag that has no 'Scope' field is an
individual language.
'Scope' information can sometimes be helpful in selecting language
tags, since it indicates the purpose or "scope" of the code
assignment within ISO 639. The available values are:
o 'macrolanguage' - Indicates a macrolanguage as defined by ISO
639-3 (see Section 3.1.10). A macrolanguage is a cluster of
closely related languages that are sometimes considered to be a
single language.
o 'collection' - Indicates a subtag that represents a collection of
languages, typically related by some type of historical,
geographical, or linguistic association. Unlike a macrolanguage,
a collection can contain languages that are only loosely related
and a collection cannot be used interchangeably with languages
that belong to it.
o 'special' - Indicates a special language code. These are subtags
used for identifying linguistic attributes not particularly
associated with a concrete language. These include codes for when
the language is undetermined or for non-linguistic content.
o 'private-use' - Indicates a code reserved for private use in the
underlying standard. Subtags with this scope can be used to
indicate a primary language for which no ISO 639 or registered
assignment exists.
The 'Scope' field MAY appear in records of type 'language' or
'extlang'. Note that many of the prefixes for extended language
subtags will have a 'Scope' of 'macrolanguage' (although some will
not) and that many languages that have a 'Scope' of 'macrolanguage'
will have extended language subtags associated with them.
The 'Scope' field MAY be added, modified, or removed via the
registration process, provided the change mirrors changes made by ISO
639 to the assignment's classification. Such a change is expected to
be rare.
For example, the primary language subtag 'zh' (Chinese) has a 'Scope'
of 'macrolanguage', while its enclosed language 'nan' (Min Nan
Chinese) has a 'Scope' of 'individual'. The special value 'und'
(Undetermined) has a 'Scope' of 'special'. The ISO 639-5 collection
'gem' (Germanic languages) has a 'Scope' of 'collection'.
3.1.12. Comments Field
The field 'Comments' contains additional information about the record
and MAY appear more than once per record. The field-body MAY include
the full range of Unicode characters and is not restricted to any
particular script. This field MAY be inserted or changed via the
registration process, and no guarantee of stability is provided.
The content of this field is not restricted, except by the need to
register the information, the suitability of the request, and by
reasonable practical size limitations. The primary reason for the
'Comments' field is subtag identification -- to help distinguish the
subtag from others with which it might be confused as an aid to
usage. Large amounts of information about the use, history, or
general background of a subtag are frowned upon, as these generally
belong in a registration request rather than in the registry.
3.2. Language Subtag Reviewer
The Language Subtag Reviewer moderates the ietf-languages@iana.org
mailing list, responds to requests for registration, and performs the
other registry maintenance duties described in Section 3.3. Only the
Language Subtag Reviewer is permitted to request IANA to change,
update, or add records to the Language Subtag Registry. The Language
Subtag Reviewer MAY delegate list moderation and other clerical
duties as needed.
The Language Subtag Reviewer is appointed by the IESG for an
indefinite term, subject to removal or replacement at the IESG's
discretion. The IESG will solicit nominees for the position (upon
adoption of this document or upon a vacancy) and then solicit
feedback on the nominees' qualifications. Qualified candidates
should be familiar with BCP 47 and its requirements; be willing to
fairly, responsively, and judiciously administer the registration
process; and be suitably informed about the issues of language
identification so that the reviewer can assess the claims and draw
upon the contributions of language experts and subtag requesters.
The subsequent performance or decisions of the Language Subtag
Reviewer MAY be appealed to the IESG under the same rules as other
IETF decisions (see [RFC2026]). The IESG can reverse or overturn the
decisions of the Language Subtag Reviewer, provide guidance, or take
other appropriate actions.
3.3. Maintenance of the Registry
Maintenance of the registry requires that, as codes are assigned or
withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language
Subtag Reviewer MUST evaluate each change and determine the
appropriate course of action according to the rules in this document.
Such updates follow the registration process described in
Section 3.5. Usually, the Language Subtag Reviewer will start the
process for the new or updated record by filling in the registration
form and submitting it. If a change to one of these standards takes
place and the Language Subtag Reviewer does not do this in a timely
manner, then any interested party MAY submit the form. Thereafter,
the registration process continues normally.
Note that some registrations affect other subtags--perhaps more than
one--as when a region subtag is being deprecated in favor of a new
value. The Language Subtag Reviewer is responsible for ensuring that
any such changes are properly registered, with each change requiring
its own registration form.
The Language Subtag Reviewer MUST ensure that new subtags meet the
requirements elsewhere in this document (and most especially in
Section 3.4) or submit an appropriate registration form for an
alternate subtag as described in that section. Each individual
subtag affected by a change MUST be sent to the
ietf-languages@iana.org list with its own registration form and in a
separate message.
3.4. Stability of IANA Registry Entries 3.4. Stability of IANA Registry Entries
The stability of entries and their meaning in the registry is The stability of entries and their meaning in the registry is
critical to the long-term stability of language tags. The rules in critical to the long-term stability of language tags. The rules in
this section guarantee that a specific language tag's meaning is this section guarantee that a specific language tag's meaning is
stable over time and will not change. stable over time and will not change.
These rules specifically deal with how changes to codes (including These rules specifically deal with how changes to codes (including
withdrawal and deprecation of codes) maintained by ISO 639, ISO withdrawal and deprecation of codes) maintained by ISO 639, ISO
15924, ISO 3166, and UN M.49 are reflected in the IANA Language 15924, ISO 3166, and UN M.49 are reflected in the IANA Language
Subtag Registry. Assignments to the IANA Language Subtag Registry Subtag Registry. Assignments to the IANA Language Subtag Registry
MUST follow the following stability rules: MUST follow the following stability rules:
1. Values in the fields 'Type', 'Subtag', 'Tag', 'Added', 1. Values in the fields 'Type', 'Subtag', 'Tag', and 'Added' MUST
'Deprecated' and 'Preferred-Value' MUST NOT be changed and are NOT be changed and are guaranteed to be stable over time.
guaranteed to be stable over time.
2. Values in the 'Description' field MUST NOT be changed in a way 2. Values in the fields 'Preferred-Value' and 'Deprecated' MAY be
that would invalidate previously-existing tags. They MAY be added, altered, or removed via the registration process. These
changes SHOULD be limited to changes necessary to mirror changes
in one of the underlying standards (ISO 639, ISO 15924, ISO
3166-1, or UN M.49) and typically alteration or removal of a
'Preferred-Value' is limited specifically to region codes.
3. Values in the 'Description' field MUST NOT be changed in a way
that would invalidate any existing tags. The description MAY be
broadened somewhat in scope, changed to add information, or broadened somewhat in scope, changed to add information, or
adapted to the most common modern usage. For example, countries adapted to the most common modern usage. For example, countries
occasionally change their official names; a historical example occasionally change their names; a historical example of this is
of this would be "Upper Volta" changing to "Burkina Faso". "Upper Volta" changing to "Burkina Faso".
3. Values in the field 'Prefix' MAY be added to records of type 4. Values in the field 'Prefix' MAY be added to existing records of
'variant' via the registration process. type 'variant' via the registration process, provided the
'variant' already has at least one 'Prefix'. A 'Prefix' field
SHALL NOT be registered for any 'variant' that has no existing
'Prefix' field. If a prefix is added to a variant record,
'Comment' fields MAY be used to explain different usages with
the various prefixes.
4. Values in the field 'Prefix' MAY be modified, so long as the 5. Values in the field 'Prefix' in records of type 'variant' MAY
modifications broaden the set of prefixes. That is, a prefix also be modified, so long as the modifications broaden the set
MAY be replaced by one of its own prefixes. For example, the of prefixes. That is, a prefix MAY be replaced by one of its
prefix "en-US" could be replaced by "en", but not by the own prefixes. For example, the prefix "en-US" could be replaced
prefixes "en-Latn", "fr", or "en-US-boont". If one of those by "en", but not by the prefixes "en-Latn", "fr", or "en-US-
prefixes were needed, a new Prefix SHOULD be registered. boont". If one of those prefix values were needed, it would
have to be separately registered.
5. Values in the field 'Prefix' MUST NOT be removed. 6. Values in the field 'Prefix' in records of type 'extlang' MUST
NOT be added, modified, or removed.
6. The field 'Comments' MAY be added, changed, modified, or removed 7. The field 'Prefix' MUST NOT be removed from any record in which
it appears. This field SHOULD be included in the initial
registration of any records of type 'variant' and MUST be
included in any records of type 'extlang'.
8. The field 'Comments' MAY be added, changed, modified, or removed
via the registration process or any of the processes or via the registration process or any of the processes or
considerations described in this section. considerations described in this section.
7. The field 'Suppress-Script' MAY be added or removed via the 9. The field 'Suppress-Script' MAY be added or removed via the
registration process. registration process.
8. Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not 10. The field 'Macrolanguage' MAY be added or removed via the
conflict with existing subtags of the associated type and whose registration process, but only in response to changes made by
meaning is not the same as an existing subtag of the same type ISO 639. The 'Macrolanguage' field appears whenever a language
are entered into the IANA registry as new records. has a corresponding macrolanguage in ISO 639. That is, the
'Macrolanguage' fields in the registry exactly match those of
ISO 639. No other macrolanguage mappings will be considered for
registration.
9. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 11. The field 'Scope' MAY be added or removed from a primary or
extended language subtag after initial registration, and it MAY
be modified in order to match any changes made by ISO 639.
Changes to the 'Scope' field MUST mirror changes made by ISO
639. Note that primary or extended language subtags whose
records do not contain a 'Scope' field (that is, most of them)
are individual languages as described in Section 3.1.11.
12. Primary and extended language subtags (other than independently
registered values created using the registration process) are
created according to the assignments of the various parts of ISO
639, as follows:
A. Codes assigned by ISO 639-1 that do not conflict with
existing two-letter primary language subtags and that have
no corresponding three-letter primary defined in the
registry are entered into the IANA registry as new records
of type 'language'. Note that languages given an ISO 639-1
code cannot be given extended language subtags, even if
encompassed by a macrolanguage.
B. Codes assigned by ISO 639-3 or ISO 639-5 that do not
conflict with existing three-letter primary language subtags
and that do not have ISO 639-1 codes assigned (or expected
to be assigned) are entered into the IANA registry as new
records of type 'language'. Note that these two standards
now comprise a superset of ISO 639-2 codes. Codes that have
a defined 'macrolanguage' mapping at the time of their
registration MUST contain a 'Macrolanguage' field.
C. Codes assigned by ISO 639-3 MAY also be considered for an
extended language subtag registration. Note that they MUST
be assigned a primary language subtag record of type
'language' even when an 'extlang' record is proposed. When
considering extended language subtag assignment, these
criteria apply:
1. If a language has a macrolanguage mapping, and that
macrolanguage has other encompassed languages that are
assigned extended language subtags, then the new
language SHOULD have an 'extlang' record assigned to it
as well. For example, any language with a macrolanguage
of 'zh' or 'ar' would be assigned an 'extlang' record.
2. 'Extlang' records SHOULD NOT be created for languages if
other languages encompassed by the macrolanguage do not
also include 'extlang' records. For example, if a new
Serbo-Croatian ('sh') language were registered, it would
not get an extlang record because other languages
encompassed, such as Serbian ('sr'), do not include one
in the registry.
3. Sign languages SHOULD have an 'extlang' record with a
'Prefix' of 'sgn'.
4. 'Extlang' records MUST NOT be created for items already
in the registry. Extended language subtags will only be
considered at the time of initial registration.
5. Extended language subtag records MUST include the fields
'Prefix' and 'Preferred-Value' with field values
assigned as described in Section 2.2.2.
D. Any other codes assigned by ISO 639-2 that do not conflict
with existing three-letter primary or extended language
subtags and that do not have ISO 639-1 two-letter codes
assigned are entered into the IANA registry as new records
of type 'language'. This type of registration is not
supposed to occur in the future.
13. Codes assigned by ISO 15924 and ISO 3166-1 that do not conflict
with existing subtags of the associated type and whose meaning
is not the same as an existing subtag of the same type are
entered into the IANA registry as new records.
14. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that are
withdrawn by their respective maintenance or registration withdrawn by their respective maintenance or registration
authority remain valid in language tags. A 'Deprecated' field authority remain valid in language tags. A 'Deprecated' field
containing the date of withdrawal is added to the record. If a containing the date of withdrawal MUST be added to the record.
new record of the same type is added that represents a If a new record of the same type is added that represents a
replacement value, then a 'Preferred-Value' field MAY also be replacement value, then a 'Preferred-Value' field MAY also be
added. The registration process MAY be used to add comments added. The registration process MAY be used to add comments
about the withdrawal of the code by the respective standard. about the withdrawal of the code by the respective standard.
Example For example: the region code 'TL' was assigned to the country
The region code 'TL' was assigned to the country 'Timor- 'Timor-Leste', replacing the code 'TP' (which was assigned to
Leste', replacing the code 'TP' (which was assigned to 'East 'East Timor' when it was under administration by Portugal).
Timor' when it was under administration by Portugal). The The subtag 'TP' remains valid in language tags, but its
subtag 'TP' remains valid in language tags, but its record record contains the 'Preferred-Value' of 'TL' and its field
contains the a 'Preferred-Value' of 'TL' and its field
'Deprecated' contains the date the new code was assigned 'Deprecated' contains the date the new code was assigned
('2004-07-06'). ('2004-07-06').
10. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 15. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that
with existing subtags of the associated type, including subtags conflict with existing subtags of the associated type, including
that are deprecated, MUST NOT be entered into the registry. The subtags that are deprecated, MUST NOT be entered into the
following additional considerations apply to subtag values that registry. The following additional considerations apply to
are reassigned: subtag values that are reassigned:
A. For ISO 639 codes, if the newly assigned code's meaning is A. For ISO 639 codes, if the newly assigned code's meaning is
not represented by a subtag in the IANA registry, the not represented by a subtag in the IANA registry, the
Language Subtag Reviewer, as described in Section 3.5, SHALL Language Subtag Reviewer, as described in Section 3.5, SHALL
prepare a proposal for entering in the IANA registry as soon prepare a proposal for entering in the IANA registry, as
as practical a registered language subtag as an alternate soon as practical, a registered language subtag as an
value for the new code. The form of the registered language alternate value for the new code. The form of the
subtag will be at the discretion of the Language Subtag registered language subtag will be at the discretion of the
Reviewer and MUST conform to other restrictions on language Language Subtag Reviewer and MUST conform to other
subtags in this document. restrictions on language subtags in this document.
B. For all subtags whose meaning is derived from an external B. For all subtags whose meaning is derived from an external
standard (i.e., ISO 639, ISO 15924, ISO 3166, or UN M.49), standard (that is, by ISO 639, ISO 15924, ISO 3166-1, or UN
if a new meaning is assigned to an existing code and the new M.49), if a new meaning is assigned to an existing code and
meaning broadens the meaning of that code, then the meaning the new meaning broadens the meaning of that code, then the
for the associated subtag MAY be changed to match. The meaning for the associated subtag MAY be changed to match.
meaning of a subtag MUST NOT be narrowed, however, as this
can result in an unknown proportion of the existing uses of The meaning of a subtag MUST NOT be narrowed, however, as
a subtag becoming invalid. Note: ISO 639 maintenance this can result in an unknown proportion of the existing
agency/registration authority (MA/RA) has adopted a similar uses of a subtag becoming invalid. Note: the ISO 639
stability policy. registration authority (RA) has adopted a similar stability
policy.
C. For ISO 15924 codes, if the newly assigned code's meaning is C. For ISO 15924 codes, if the newly assigned code's meaning is
not represented by a subtag in the IANA registry, the not represented by a subtag in the IANA registry, the
Language Subtag Reviewer, as described in Section 3.5, SHALL Language Subtag Reviewer, as described in Section 3.5, SHALL
prepare a proposal for entering in the IANA registry as soon prepare a proposal for entering in the IANA registry, as
as practical a registered variant subtag as an alternate soon as practical, a registered variant subtag as an
value for the new code. The form of the registered variant alternate value for the new code. The form of the
subtag will be at the discretion of the Language Subtag registered variant subtag will be at the discretion of the
Reviewer and MUST conform to other restrictions on variant Language Subtag Reviewer and MUST conform to other
subtags in this document. restrictions on variant subtags in this document.
D. For ISO 3166 codes, if the newly assigned code's meaning is D. For ISO 3166-1 codes, if the newly assigned code's meaning
associated with the same UN M.49 code as another 'region' is associated with the same UN M.49 code as another 'region'
subtag, then the existing region subtag remains as the subtag, then the existing region subtag remains as the
preferred value for that region and no new entry is created. preferred value for that region and no new entry is created.
A comment MAY be added to the existing region subtag A comment MAY be added to the existing region subtag
indicating the relationship to the new ISO 3166 code. indicating the relationship to the new ISO 3166-1 code.
E. For ISO 3166 codes, if the newly assigned code's meaning is E. For ISO 3166-1 codes, if the newly assigned code's meaning
associated with a UN M.49 code that is not represented by an is associated with a UN M.49 code that is not represented by
existing region subtag, then the Language Subtag Reviewer, an existing region subtag, then the Language Subtag
as described in Section 3.5, SHALL prepare a proposal for Reviewer, as described in Section 3.5, SHALL prepare a
entering the appropriate UN M.49 country code as an entry in proposal for entering the appropriate UN M.49 country code
the IANA registry. as an entry in the IANA registry.
F. For ISO 3166 codes, if there is no associated UN numeric F. For ISO 3166-1 codes, if there is no associated UN numeric
code, then the Language Subtag Reviewer SHALL petition the code, then the Language Subtag Reviewer SHALL petition the
UN to create one. If there is no response from the UN UN to create one. If there is no response from the UN
within ninety days of the request being sent, the Language within 90 days of the request being sent, the Language
Subtag Reviewer SHALL prepare a proposal for entering in the Subtag Reviewer SHALL prepare a proposal for entering in the
IANA registry as soon as practical a registered variant IANA registry, as soon as practical, a registered variant
subtag as an alternate value for the new code. The form of subtag as an alternate value for the new code. The form of
the registered variant subtag will be at the discretion of the registered variant subtag will be at the discretion of
the Language Subtag Reviewer and MUST conform to other the Language Subtag Reviewer and MUST conform to other
restrictions on variant subtags in this document. This restrictions on variant subtags in this document. This
situation is very unlikely to ever occur. situation is very unlikely to ever occur.
11. UN M.49 has codes for both countries and areas (such as '276' 16. UN M.49 has codes for both "countries and areas" (such as '276'
for Germany) and geographical regions and sub-regions (such as for Germany) and "geographical regions and sub-regions" (such as
'150' for Europe). UN M.49 country or area codes for which '150' for Europe). UN M.49 country or area codes for which
there is no corresponding ISO 3166 code SHOULD NOT be there is no corresponding ISO 3166-1 code MUST NOT be
registered, except as a surrogate for an ISO 3166 code that is registered, except as a surrogate for an ISO 3166-1 code that is
blocked from registration by an existing subtag. If such a code blocked from registration by an existing subtag.
becomes necessary, then the registration authority for ISO 3166
SHOULD first be petitioned to assign a code to the region. If If such a code becomes necessary, then the maintenance agency
the petition for a code assignment by ISO 3166 is refused or not for ISO 3166-1 SHALL first be petitioned to assign a code to the
acted on in a timely manner, the registration process described region. If the petition for a code assignment by ISO 3166-1 is
in Section 3.5 MAY then be used to register the corresponding UN refused or not acted on in a timely manner, the registration
M.49 code. At the time this document was written, there were process described in Section 3.5 can then be used to register
only four such codes: 830 (Channel Islands), 831 (Guernsey), 832 the corresponding UN M.49 code. This way, UN M.49 codes remain
(Jersey), and 833 (Isle of Man). This way, UN M.49 codes remain available as the value of last resort in cases where ISO 3166-1
available as the value of last resort in cases where ISO 3166
reassigns a deprecated value in the registry. reassigns a deprecated value in the registry.
12. Stability provisions apply to grandfathered tags with this 17. The redundant and grandfathered entries together form the
exception: should all of the subtags in a grandfathered tag complete list of tags registered under [RFC3066]. The redundant
become valid subtags in the IANA registry, then the field 'Type' tags are those previously registered tags that can now be formed
in that record is changed from 'grandfathered' to 'redundant'. using the subtags defined in the registry. The grandfathered
Note that this will not affect language tags that match the entries include those that can never be legal because they are
grandfathered tag, since these tags will now match valid 'irregular' (that is, they do not match the 'langtag' production
generative subtag sequences. For example, if the subtag 'gan' in Figure 1), are limited by rule (subtags such as 'nyn' and
in the language tag "zh-gan" were to be registered as an 'min' look like the extlang production, but cannot be registered
extended language subtag, then the grandfathered tag "zh-gan" as extended language subtags), or their subtags are
would be deprecated (but existing content or implementations inappropriate for registration. All of the grandfathered tags
that use "zh-gan" would remain valid). are listed in either the 'regular' or the 'irregular'
productions in the ABNF. Under [RFC4646] it was possible for
grandfathered tags to become redundant. However, all of the
tags for which this was possible became redundant before this
document was produced. So the set of redundant and
grandfathered tags is now permanent and immutable: new entries
of either type MUST NOT be added and existing entries MUST NOT
be removed. The decision-making process about which tags were
initially grandfathered and which were made redundant is
described in [RFC4645].
Many of the grandfathered tags are deprecated -- indeed, they
were deprecated even before [RFC4646]. For example, the tag
"art-lojban" was deprecated in favor of the primary language
subtag 'jbo'. These tags could have been made 'redundant' by
registering some of their subtags as 'variants'. The 'variant-
like' subtags in the grandfathered registrations SHALL NOT be
registered in the future, even with a similar or identical
meaning.
3.5. Registration Procedure for Subtags 3.5. Registration Procedure for Subtags
The procedure given here MUST be used by anyone who wants to use a The procedure given here MUST be used by anyone who wants to use a
subtag not currently in the IANA Language Subtag Registry. subtag not currently in the IANA Language Subtag Registry or who
wishes to add, modify, update, or remove information in existing
records as permitted by this document.
Only subtags of type 'language' and 'variant' will be considered for Only subtags of type 'language' and 'variant' will be considered for
independent registration of new subtags. Handling of subtags needed independent registration of new subtags. Subtags needed for
for stability and subtags necessary to keep the registry synchronized stability and subtags necessary to keep the registry synchronized
with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits
defined by this document are described in Section 3.3. Stability defined by this document also use this process, as described in
provisions are described in Section 3.4. Section 3.3 and subject to stability provisions as described in
Section 3.4.
This procedure MAY also be used to register or alter the information Registration requests are accepted relating to information in the
for the 'Description', 'Comments', 'Deprecated', or 'Prefix' fields 'Comments', 'Deprecated', 'Description', 'Prefix', 'Preferred-Value',
in a subtag's record as described in Section 3.4. Changes to all 'Macrolanguage', or 'Suppress-Script' fields in a subtag's record as
other fields in the IANA registry are NOT permitted. described in Section 3.4. Changes to all other fields in the IANA
registry are NOT permitted.
Registering a new subtag or requesting modifications to an existing Registering a new subtag or requesting modifications to an existing
tag or subtag starts with the requester filling out the registration tag or subtag starts with the requester filling out the registration
form reproduced below. Note that each response is not limited in form reproduced below. Note that each response is not limited in
size so that the request can adequately describe the registration. size so that the request can adequately describe the registration.
The fields in the "Record Requested" section SHOULD follow the The fields in the "Record Requested" section need to follow the
requirements in Section 3.1. requirements in Section 3.1 before the record will be approved.
LANGUAGE SUBTAG REGISTRATION FORM LANGUAGE SUBTAG REGISTRATION FORM
1. Name of requester: 1. Name of requester:
2. E-mail address of requester: 2. E-mail address of requester:
3. Record Requested: 3. Record Requested:
Type: Type:
Subtag: Subtag:
Description: Description:
Prefix: Prefix:
Preferred-Value: Preferred-Value:
Deprecated: Deprecated:
Suppress-Script: Suppress-Script:
Macrolanguage:
Comments: Comments:
4. Intended meaning of the subtag: 4. Intended meaning of the subtag:
5. Reference to published description 5. Reference to published description
of the language (book or article): of the language (book or article):
6. Any other relevant information: 6. Any other relevant information:
Figure 5: The Language Subtag Registration Form Figure 5: The Language Subtag Registration Form
Examples of completed registration forms can be found in Appendix B.
A complete list of approved registration forms is online through
http://www.iana.org; readers should note that the Language Tag
Registry is now obsolete and should instead look for the Language
Subtag Registry.
The subtag registration form MUST be sent to The subtag registration form MUST be sent to
<ietf-languages@iana.org> for a two-week review period before it can <ietf-languages@iana.org>. Registration requests receive a two-week
be submitted to IANA. (This is an open list and can be joined by review period before being approved and submitted to IANA for
sending a request to <ietf-languages-request@iana.org>.) inclusion in the registry. If modifications are made to the request
during the course of the registration process (such as corrections to
meet the requirements in Section 3.1 or to make the 'Description'
fields unique for the given record type), the modified form MUST also
be sent to <ietf-languages@iana.org> at least one week prior to
submission to IANA.
The ietf-languages list is an open list and can be joined by sending
a request to <ietf-languages-request@iana.org>. The list can be
hosted by IANA or any third party at the request of IESG.
Before forwarding any registration to IANA, the Language Subtag
Reviewer MUST ensure that all requirements in this document are met.
This includes ensuring that values in the 'Subtag' field match case
according to the description in Section 3.1.4 and that 'Description'
fields are unique for the given record type as described in
Section 3.1.5. The Reviewer MUST also ensure that an appropriate
File-Date record is included in the request, to assist IANA when
updating the registry (see Section 5.1).
Some fields in both the registration form as well as the registry
record itself permit the use of non-ASCII characters. Registration
requests SHOULD use the UTF-8 encoding for consistency and clarity.
However, since some mail clients do not support this encoding, other
encodings MAY be used for the registration request. The Language
Subtag Reviewer is responsible for ensuring that the proper Unicode
characters appear in both the archived request form and the registry
record. In the case of a transcription or encoding error by IANA,
the Language Subtag Reviewer will request that the registry be
repaired, providing any necessary information to assist IANA.
Extended language subtags (type 'extlang'), by definition, are always
encompassed by another language. All records of type 'extlang' MUST,
therefore, contain a 'Prefix' field at the time of registration.
This 'Prefix' field can never be altered or removed, and requests to
do so MUST be rejected.
Variant subtags are usually registered for use with a particular Variant subtags are usually registered for use with a particular
range of language tags. For example, the subtag 'rozaj' is intended range of language tags, and variant subtags based on the terminology
for use with language tags that start with the primary language of the language to which they are apply are encouraged. For example,
subtag "sl", since Resian is a dialect of Slovenian. Thus, the the subtag 'rozaj' (Resian) is intended for use with language tags
subtag 'rozaj' would be appropriate in tags such as "sl-Latn-rozaj" that start with the primary language subtag "sl" (Slovenian), since
or "sl-IT-rozaj". This information is stored in the 'Prefix' field Resian is a dialect of Slovenian. Thus, the subtag 'rozaj' would be
in the registry. Variant registration requests SHOULD include at appropriate in tags such as "sl-Latn-rozaj" or "sl-IT-rozaj". This
least one 'Prefix' field in the registration form. information is stored in the 'Prefix' field in the registry. Variant
registration requests SHOULD include at least one 'Prefix' field in
the registration form.
Extended language subtags are reserved for future standardization. Requests to assign an additional record of a given type with an
These subtags will be REQUIRED to include exactly one 'Prefix' field existing subtag value MUST be rejected. For example, the variant
once they are allowed for registration. subtag 'rozaj' already exists in the registry, so adding a second
record of type 'variant' with the subtag 'rozaj' is prohibited.
The 'Prefix' field for a given registered subtag exists in the IANA The 'Prefix' field for a given registered variant subtag exists in
registry as a guide to usage. Additional prefixes MAY be added by the IANA registry as a guide to usage. Additional 'Prefix' fields
filing an additional registration form. In that form, the "Any other MAY be added by filing an additional registration form. In that
relevant information:" field MUST indicate that it is the addition of form, the "Any other relevant information:" field MUST indicate that
a prefix. it is the addition of a prefix.
Requests to add a prefix to a variant subtag that imply a different Requests to add a 'Prefix' field to a variant subtag that imply a
semantic meaning will probably be rejected. For example, a request different semantic meaning SHOULD be rejected. For example, a
to add the prefix "de" to the subtag 'nedis' so that the tag request to add the prefix "de" to the subtag '1994' so that the tag
"de-nedis" represented some German dialect would be rejected. The "de-1994" represented some German dialect or orthographic form would
'nedis' subtag represents a particular Slovenian dialect and the be rejected. The '1994' subtag represents a particular Slovenian
additional registration would change the semantic meaning assigned to orthography, and the additional registration would change or blur the
the subtag. A separate subtag SHOULD be proposed instead. semantic meaning assigned to the subtag. A separate subtag SHOULD be
proposed instead.
The 'Description' field MUST contain a description of the tag being Requests to add a 'Prefix' to a variant subtag that has no current
registered written or transcribed into the Latin script; it MAY also 'Prefix' field MUST be rejected. Variants are registered with no
include a description in a non-Latin script. Non-ASCII characters prefix because they are potentially useful with many or even all
MUST be escaped using the syntax described in Section 3.1. The languages. Adding one or more 'Prefix' fields would be potentially
'Description' field is used for identification purposes and doesn't harmful to the use of the variant, since it dramatically reduces the
necessarily represent the actual native name of the language or scope of the subtag (which is not allowed under the stability rules
variation or to be in any particular language. (Section 3.4) as opposed to broadening the scope of the subtag, which
is what the addition of a 'Prefix' normally does. An example of such
a "no-prefix" variant is the subtag 'fonipa', which represents the
International Phonetic Alphabet, a scheme that can be used to
transcribe many languages.
While the 'Description' field itself is not guaranteed to be stable The 'Description' fields provided in the request MUST contain at
and errata corrections MAY be undertaken from time to time, attempts least one description written or transcribed into the Latin script;
to provide translations or transcriptions of entries in the registry the request MAY also include additional 'Description' fields in any
itself will probably be frowned upon by the community or rejected script or language. The 'Description' field is used for
outright, as changes of this nature have an impact on the provisions identification purposes and doesn't necessarily represent the actual
in Section 3.4. native name of the language or variation. It also doesn't have to be
in any particular language, but SHOULD be both suitable and
sufficient to identify the item in the record. The Language Subtag
Reviewer will check and edit any proposed 'Description' fields so as
to ensure uniqueness and prevent collisions with 'Description' fields
in other records of the same type. If this occurs in an independent
registration request, the Language Subtag Reviewer MUST resubmit the
record to <ietf-languages@iana.org>, treating it as a modification of
a request due to discussion, as described in Section 3.5, unless the
request's sole purpose is to introduce a duplicate 'Description'
field, in which case the request SHALL be rejected.
When the two-week period has passed, the Language Subtag Reviewer The 'Description' field is not guaranteed to be stable. Corrections
either forwards the record to be inserted or modified to or clarifications of intent are examples of possible changes.
iana@iana.org according to the procedure described in Section 3.3, or Attempts to provide translations or transcriptions of entries in the
rejects the request because of significant objections raised on the registry (which, by definition, provide no new information) are
list or due to problems with constraints in this document (which MUST unlikely to be approved.
be explicitly cited). The Language Subtag Reviewer MAY also extend
the review period in two-week increments to permit further Soon after the two-week review period has passed, the Language Subtag
discussion. The Language Subtag Reviewer MUST indicate on the list Reviewer MUST take one of the following actions:
whether the registration has been accepted, rejected, or extended
following each two-week period. o Explicitly accept the request and forward the form containing the
record to be inserted or modified to <iana@iana.org> according to
the procedure described in Section 3.3.
o Explicitly reject the request because of significant objections
raised on the list or due to problems with constraints in this
document (which MUST be explicitly cited).
o Extend the review period by granting an additional two-week
increment to permit further discussion. After each two-week
increment, the Language Subtag Reviewer MUST indicate on the list
whether the registration has been accepted, rejected, or extended.
Note that the Language Subtag Reviewer MAY raise objections on the Note that the Language Subtag Reviewer MAY raise objections on the
list if he or she so desires. The important thing is that the list if he or she so desires. The important thing is that the
objection MUST be made publicly. objection MUST be made publicly.
The applicant is free to modify a rejected application with Sometimes the request needs to be modified as a result of discussion
additional information and submit it again; this restarts the two- during the review period or due to requirements in this document.
The applicant, Language Subtag Reviewer, or others MAY submit a
modified version of the completed registration form, which will be
considered in lieu of the original request with the explicit approval
of the applicant. Such changes do not restart the two-week
discussion period, although an application containing the final
record submitted to IANA MUST appear on the list at least one week
prior to the Language Subtag Reviewer forwarding the record to IANA.
The applicant MAY modify a rejected application with more appropriate
or additional information and submit it again; this starts a new two-
week comment period. week comment period.
Registrations initiated due to the provisions of Section 3.3 or
Section 3.4 SHALL NOT be rejected altogether (since they have to
ultimately appear in the registry) and SHOULD be completed as quickly
as possible. The review process allows list members to comment on
the specific information in the form and the record it contains and
thus help ensure that it is correct and consistent. The Language
Subtag Reviewer MAY reject a specific version of the form, but MUST
propose a suitable replacement, extending the review period as
described above, until the form is in a format worthy of the
reviewer's approval and meets with rough consensus of the list.
Decisions made by the Language Subtag Reviewer MAY be appealed to the Decisions made by the Language Subtag Reviewer MAY be appealed to the
IESG [RFC2028] under the same rules as other IETF decisions IESG [RFC2028] under the same rules as other IETF decisions
[RFC2026]. [RFC2026]. This includes a decision to extend the review period or
the failure to announce a decision in a clear and timely manner.
All approved registration forms are available online in the directory The approved records appear in the Language Subtag Registry. The
http://www.iana.org/numbers.html under "languages". approved registration forms are available online from
http://www.iana.org.
Updates or changes to existing records follow the same procedure as Updates or changes to existing records follow the same procedure as
new registrations. The Language Subtag Reviewer decides whether new registrations. The Language Subtag Reviewer decides whether
there is consensus to update the registration following the two-week there is consensus to update the registration following the two-week
review period; normally, objections by the original registrant will review period; normally, objections by the original registrant will
carry extra weight in forming such a consensus. carry extra weight in forming such a consensus.
Registrations are permanent and stable. Once registered, subtags Registrations are permanent and stable. Once registered, subtags
will not be removed from the registry and will remain a valid way in will not be removed from the registry and will remain a valid way in
which to specify a specific language or variant. which to specify a specific language or variant.
Note: The purpose of the "Description" in the registration form is to Note: The purpose of the "Reference to published description" section
aid people trying to verify whether a language is registered or what in the registration form is to aid in verifying whether a language is
language or language variation a particular subtag refers to. In registered or to which language or language variation a particular
most cases, reference to an authoritative grammar or dictionary of subtag refers. In most cases, reference to an authoritative grammar
that language will be useful; in cases where no such work exists, or dictionary of that language will be useful; in cases where no such
other well-known works describing that language or in that language work exists, other well-known works describing that language or in
MAY be appropriate. The Language Subtag Reviewer decides what that language MAY be appropriate. The Language Subtag Reviewer
constitutes "good enough" reference material. This requirement is decides what constitutes "good enough" reference material. This
not intended to exclude particular languages or dialects due to the requirement is not intended to exclude particular languages or
size of the speaker population or lack of a standardized orthography. dialects due to the size of the speaker population or lack of a
Minority languages will be considered equally on their own merits. standardized orthography. Minority languages will be considered
equally on their own merits.
3.6. Possibilities for Registration 3.6. Possibilities for Registration
Possibilities for registration of subtags or information about Possibilities for registration of subtags or information about
subtags include: subtags include:
o Primary language subtags for languages not listed in ISO 639 that o Primary language subtags for languages not listed in ISO 639 that
are not variants of any listed or registered language MAY be are not variants of any listed or registered language MAY be
registered. At the time this document was created, there were no registered. At the time this document was created, there were no
examples of this form of subtag. Before attempting to register a examples of this form of subtag. Before attempting to register a
language subtag, there MUST be an attempt to register the language language subtag, there MUST be an attempt to register the language
with ISO 639. Subtags MUST NOT be registered for codes that exist with ISO 639. Subtags MUST NOT be registered for languages
in ISO 639-1 or ISO 639-2, that are under consideration by the ISO defined by codes that exist in ISO 639-1, ISO 639-2, or ISO 639-3;
639 maintenance or registration authorities, or that have never that are under consideration by the ISO 639 registration
been attempted for registration with those authorities. If ISO authorities; or that have never been attempted for registration
639 has previously rejected a language for registration, it is with those authorities. If ISO 639 has previously rejected a
reasonable to assume that there must be additional, very language for registration, it is reasonable to assume that there
compelling evidence of need before it will be registered in the must be additional, very compelling evidence of need before it
IANA registry (to the extent that it is very unlikely that any will be registered as a primary language subtag in the IANA
subtags will be registered of this type). registry (to the extent that it is very unlikely that any subtags
will be registered of this type).
o Dialect or other divisions or variations within a language, its o Dialect or other divisions or variations within a language, its
orthography, writing system, regional or historical usage, orthography, writing system, regional or historical usage,
transliteration or other transformation, or distinguishing transliteration or other transformation, or distinguishing
variation MAY be registered as variant subtags. An example is the variation MAY be registered as variant subtags. An example is the
'rozaj' subtag (the Resian dialect of Slovenian). 'rozaj' subtag (the Resian dialect of Slovenian).
o The addition or maintenance of fields (generally of an o The addition or maintenance of fields (generally of an
informational nature) in Tag or Subtag records as described in informational nature) in tag or subtag records as described in
Section 3.1 and subject to the stability provisions in Section 3.1 is allowed. Such changes are subject to the stability
Section 3.4. This includes descriptions, comments, deprecation provisions in Section 3.4. This includes 'Description',
and preferred values for obsolete or withdrawn codes, or the 'Comments', 'Deprecated', and 'Preferred-Value' fields for
addition of script or extlang information to primary language obsolete or withdrawn codes, or the addition of 'Suppress-Script'
subtags. or 'Macrolanguage' fields to primary language subtags, as well as
other changes permitted by this document, such as the addition of
an appropriate 'Prefix' field to a variant subtag.
o The addition of records and related field value changes necessary o The addition of records and related field value changes necessary
to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and to reflect assignments made by ISO 639, ISO 15924, ISO 3166-1, and
UN M.49 as described in Section 3.4. UN M.49 as described in Section 3.4 is allowed.
Subtags proposed for registration that would cause all or part of a Subtags proposed for registration that would cause all or part of a
grandfathered tag to become redundant but whose meaning conflicts grandfathered tag to become redundant but whose meaning conflicts
with or alters the meaning of the grandfathered tag MUST be rejected. with or alters the meaning of the grandfathered tag MUST be rejected.
This document leaves the decision on what subtags or changes to This document leaves the decision on what subtags or changes to
subtags are appropriate (or not) to the registration process subtags are appropriate (or not) to the registration process
described in Section 3.5. described in Section 3.5.
Note: four-character primary language subtags are reserved to allow Note: Four-character primary language subtags are reserved to allow
for the possibility of alpha4 codes in some future addition to the for the possibility of alpha4 codes in some future addition to the
ISO 639 family of standards. ISO 639 family of standards.
ISO 639 defines a maintenance agency for additions to and changes in ISO 639 defines a registration authority for additions to and changes
the list of languages in ISO 639. This agency is: in the list of languages in ISO 639. This agency is:
International Information Centre for Terminology (Infoterm) International Information Centre for Terminology (Infoterm)
Aichholzgasse 6/12, AT-1120 Aichholzgasse 6/12, AT-1120
Wien, Austria Wien, Austria
Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72
ISO 639-2 defines a maintenance agency for additions to and changes ISO 639-2 defines a registration authority for additions to and
in the list of languages in ISO 639-2. This agency is: changes in the list of languages in ISO 639-2. This agency is:
Library of Congress Library of Congress
Network Development and MARC Standards Office Network Development and MARC Standards Office
Washington, D.C. 20540 USA Washington, DC 20540, USA
Phone: +1 202 707 6237 Fax: +1 202 707 0115 Phone: +1 202 707 6237 Fax: +1 202 707 0115
URL: http://www.loc.gov/standards/iso639-2 URL: http://www.loc.gov/standards/iso639-2
The maintenance agency for ISO 3166 (country codes) is:
ISO 639-3 defines a registration authority for additions to and
changes in the list of languages in ISO 639-3. This agency is:
SIL International
ISO 639-3 Registrar
7500 W. Camp Wisdom Rd.
Dallas, TX 75236, USA
Phone: +1 972 708 7400, ext. 2293
Fax: +1 972 708 7546
Email: iso639-3@sil.org
URL: http://www.sil.org/iso639-3
ISO 639-5 defines a registration authority for additions to and
changes in the list of languages in ISO 639-5. This agency is the
same as for ISO 639-2 and is:
Library of Congress
Network Development and MARC Standards Office
Washington, DC 20540, USA
Phone: +1 202 707 6237
Fax: +1 202 707 0115
URL: http://www.loc.gov/standards/iso639-5
The maintenance agency for ISO 3166-1 (country codes) is:
ISO 3166 Maintenance Agency ISO 3166 Maintenance Agency
c/o International Organization for Standardization c/o International Organization for Standardization
Case postale 56 Case postale 56
CH-1211 Geneva 20 Switzerland CH-1211 Geneva 20, Switzerland
Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49
URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html
The registration authority for ISO 15924 (script codes) is: The registration authority for ISO 15924 (script codes) is:
Unicode Consortium Box 391476 Unicode Consortium
Box 391476
Mountain View, CA 94039-1476, USA Mountain View, CA 94039-1476, USA
URL: http://www.unicode.org/iso15924 URL: http://www.unicode.org/iso15924
The Statistics Division of the United Nations Secretariat maintains The Statistics Division of the United Nations Secretariat maintains
the Standard Country or Area Codes for Statistical Use and can be the Standard Country or Area Codes for Statistical Use and can be
reached at: reached at:
Statistical Services Branch Statistical Services Branch
Statistics Division Statistics Division
United Nations, Room DC2-1620 United Nations, Room DC2-1620
skipping to change at page 34, line 27 skipping to change at page 49, line 19
URL: http://www.unicode.org/iso15924 URL: http://www.unicode.org/iso15924
The Statistics Division of the United Nations Secretariat maintains The Statistics Division of the United Nations Secretariat maintains
the Standard Country or Area Codes for Statistical Use and can be the Standard Country or Area Codes for Statistical Use and can be
reached at: reached at:
Statistical Services Branch Statistical Services Branch
Statistics Division Statistics Division
United Nations, Room DC2-1620 United Nations, Room DC2-1620
New York, NY 10017, USA New York, NY 10017, USA
Fax: +1-212-963-0623 Fax: +1-212-963-0623
E-mail: statistics@un.org Email: statistics@un.org
URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm
3.7. Extensions and Extensions Registry 3.7. Extensions and the Extensions Registry
Extension subtags are those introduced by single-character subtags Extension subtags are those introduced by single-character subtags
("singletons") other than 'x'. They are reserved for the generation ("singletons") other than 'x'. They are reserved for the generation
of identifiers that contain a language component and are compatible of identifiers that contain a language component and are compatible
with applications that understand language tags. with applications that understand language tags.
The structure and form of extensions are defined by this document so The structure and form of extensions are defined by this document so
that implementations can be created that are forward compatible with that implementations can be created that are forward compatible with
applications that might be created using singletons in the future. applications that might be created using singletons in the future.
In addition, defining a mechanism for maintaining singletons will In addition, defining a mechanism for maintaining singletons will
lend stability to this document by reducing the likely need for lend stability to this document by reducing the likely need for
future revisions or updates. future revisions or updates.
Single-character subtags are assigned by IANA using the "IETF Single-character subtags are assigned by IANA using the "IETF Review"
Consensus" policy defined by [RFC2434]. This policy requires the policy defined by [RFC5226]. This policy requires the development of
development of an RFC, which SHALL define the name, purpose, an RFC, which SHALL define the name, purpose, processes, and
processes, and procedures for maintaining the subtags. The procedures for maintaining the subtags. The maintaining or
maintaining or registering authority, including name, contact email, registering authority, including name, contact email, discussion list
discussion list email, and URL location of the registry, MUST be email, and URL location of the registry, MUST be indicated clearly in
indicated clearly in the RFC. The RFC MUST specify or include each the RFC. The RFC MUST specify or include each of the following:
of the following:
o The specification MUST reference the specific version or revision o The specification MUST reference the specific version or revision
of this document that governs its creation and MUST reference this of this document that governs its creation and MUST reference this
section of this document. section of this document.
o The specification and all subtags defined by the specification o The specification and all subtags defined by the specification
MUST follow the ABNF and other rules for the formation of tags and MUST follow the ABNF and other rules for the formation of tags and
subtags as defined in this document. In particular, it MUST subtags as defined in this document. In particular, it MUST
specify that case is not significant and that subtags MUST NOT specify that case is not significant and that subtags MUST NOT
exceed eight characters in length. exceed eight characters in length.
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royalty-free license acceptable to the IETF and specified in the royalty-free license acceptable to the IETF and specified in the
RFC. RFC.
o The specification MUST be versioned, and each version of the o The specification MUST be versioned, and each version of the
specification MUST be numbered, dated, and stable. specification MUST be numbered, dated, and stable.
o The specification MUST be stable. That is, extension subtags, o The specification MUST be stable. That is, extension subtags,
once defined by a specification, MUST NOT be retracted or change once defined by a specification, MUST NOT be retracted or change
in meaning in any substantial way. in meaning in any substantial way.
o The specification MUST include in a separate section the o The specification MUST include, in a separate section, the
registration form reproduced in this section (below) to be used in registration form reproduced in this section (below) to be used in
registering the extension upon publication as an RFC. registering the extension upon publication as an RFC.
o IANA MUST be informed of changes to the contact information and o IANA MUST be informed of changes to the contact information and
URL for the specification. URL for the specification.
IANA will maintain a registry of allocated single-character IANA will maintain a registry of allocated single-character
(singleton) subtags. This registry MUST use the record-jar format (singleton) subtags. This registry MUST use the record-jar format
described by the ABNF in Section 3.1. Upon publication of an described by the ABNF in Section 3.1.1. Upon publication of an
extension as an RFC, the maintaining authority defined in the RFC extension as an RFC, the maintaining authority defined in the RFC
MUST forward this registration form to iesg@ietf.org, who MUST MUST forward this registration form to <iesg@ietf.org>, who MUST
forward the request to iana@iana.org. The maintaining authority of forward the request to <iana@iana.org>. The maintaining authority of
the extension MUST maintain the accuracy of the record by sending an the extension MUST maintain the accuracy of the record by sending an
updated full copy of the record to iana@iana.org with the subject updated full copy of the record to <iana@iana.org> with the subject
line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only
the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY
be modified in these updates. be modified in these updates.
Failure to maintain this record, maintain the corresponding registry, Failure to maintain this record, maintain the corresponding registry,
or meet other conditions imposed by this section of this document MAY or meet other conditions imposed by this section of this document MAY
be appealed to the IESG [RFC2028] under the same rules as other IETF be appealed to the IESG [RFC2028] under the same rules as other IETF
decisions (see [RFC2026]) and MAY result in the authority to maintain decisions (see [RFC2026]) and MAY result in the authority to maintain
the extension being withdrawn or reassigned by the IESG. the extension being withdrawn or reassigned by the IESG.
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'Identifier' contains the single-character subtag (singleton) 'Identifier' contains the single-character subtag (singleton)
assigned to the extension. The Internet-Draft submitted to define assigned to the extension. The Internet-Draft submitted to define
the extension SHOULD specify which letter or digit to use, although the extension SHOULD specify which letter or digit to use, although
the IESG MAY change the assignment when approving the RFC. the IESG MAY change the assignment when approving the RFC.
'Description' contains the name and description of the extension. 'Description' contains the name and description of the extension.
'Comments' is an OPTIONAL field and MAY contain a broader description 'Comments' is an OPTIONAL field and MAY contain a broader description
of the extension. of the extension.
'Added' contains the date the RFC was published in the "full-date" 'Added' contains the date the extension's RFC was published in the
format specified in [RFC3339]. For example: 2004-06-28 represents "full-date" format specified in [RFC3339]. For example: 2004-06-28
June 28, 2004, in the Gregorian calendar. represents June 28, 2004, in the Gregorian calendar.
'RFC' contains the RFC number assigned to the extension. 'RFC' contains the RFC number assigned to the extension.
'Authority' contains the name of the maintaining authority for the 'Authority' contains the name of the maintaining authority for the
extension. extension.
'Contact_Email' contains the email address used to contact the 'Contact_Email' contains the email address used to contact the
maintaining authority. maintaining authority.
'Mailing_List' contains the URL or subscription email address of the 'Mailing_List' contains the URL or subscription email address of the
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or meaning inherent in the order of extension subtags. Extension or meaning inherent in the order of extension subtags. Extension
authors SHOULD avoid subtag relationships or canonicalization authors SHOULD avoid subtag relationships or canonicalization
mechanisms that interfere with matching or with length restrictions mechanisms that interfere with matching or with length restrictions
that sometimes exist in common protocols where the extension is used. that sometimes exist in common protocols where the extension is used.
In particular, applications MAY truncate the subtags in doing In particular, applications MAY truncate the subtags in doing
matching or in fitting into limited lengths, so it is RECOMMENDED matching or in fitting into limited lengths, so it is RECOMMENDED
that the most significant information be in the most significant that the most significant information be in the most significant
(left-most) subtags and that the specification gracefully handle (left-most) subtags and that the specification gracefully handle
truncated subtags. truncated subtags.
When a language tag is to be used in a specific, known, protocol, it When a language tag is to be used in a specific, known protocol, it
is RECOMMENDED that the language tag not contain extensions not is RECOMMENDED that the language tag not contain extensions not
supported by that protocol. In addition, note that some protocols supported by that protocol. In addition, note that some protocols
MAY impose upper limits on the length of the strings used to store or MAY impose upper limits on the length of the strings used to store or
transport the language tag. transport the language tag.
3.8. Initialization of the Registries 3.8. Update of the Language Subtag Registry
Upon adoption of this document, an initial version of the Language After the adoption of this document, the IANA Language Subtag
Subtag Registry containing the various subtags initially valid in a Registry needed an update so that it would contain the complete set
language tag is necessary. This collection of subtags, along with a of subtags valid in a language tag. [RFC5645] describes the process
description of the process used to create it, is described by used to create this update.
[RFC4645]. IANA SHALL publish the initial version of the registry
described by this document from the content of [RFC4645]. Once
published by IANA, the maintenance procedures, rules, and
registration processes described in this document will be available
for new registrations or updates.
Registrations that are in process under the rules defined in Registrations that are in process under the rules defined in
[RFC3066] when this document is adopted MAY be completed under the [RFC4646] when this document is adopted MUST be completed under the
former rules, at the discretion of the Language Tag Reviewer (as rules contained in this document.
described in [RFC3066]). Until the IESG officially appoints a
Language Subtag Reviewer, the existing Language Tag Reviewer SHALL
serve as the Language Subtag Reviewer.
Any new registrations submitted using the RFC 3066 forms or format 3.9. Applicability of the Subtag Registry
after the adoption of this document and publication of the registry
by IANA MUST be rejected.
An initial version of the Language Tag Extensions Registry described The Language Subtag Registry is the source of data elements used to
in Section 3.7 is also needed. The Language Tag Extensions Registry construct language tags, following the rules described in this
SHALL be initialized with a single record containing a single field document. Language tags are designed for indicating linguistic
of type "File-Date" as a placeholder for future assignments. attributes of various content, including not only text but also most
media formats, such as video or audio. They also form the basis for
language and locale negotiation in various protocols and APIs.
The registry is therefore applicable to many applications that need
some form of language identification, with these limitations:
o It is not designed to be the sole data source in the creation of a
language-selection user interface. For example, the registry does
not contain translations for subtag descriptions or for tags
composed from the subtags. Sources for localized data based on
the registry are generally available, notably [CLDR]. Nor does
the registry indicate which subtag combinations are particularly
useful or relevant.
o It does not provide information indicating relationships between
different languages, such as might be used in a user interface to
select language tags hierarchically, regionally, or on some other
organizational model.
o It does not supply information about potential overlap between
different language tags, as the notion of what constitutes a
language is not precise: several different language tags might be
reasonable choices for the same given piece of content.
o It does not contain information about appropriate fallback choices
when performing language negotiation. A good fallback language
might be linguistically unrelated to the specified language. The
fact that one language is often used as a fallback language for
another is usually a result of outside factors, such as geography,
history, or culture -- factors that might not apply in all cases.
For example, most people who use Breton (a Celtic language used in
the Northwest of France) would probably prefer to be served French
(a Romance language) if Breton isn't available.
4. Formation and Processing of Language Tags 4. Formation and Processing of Language Tags
This section addresses how to use the information in the registry This section addresses how to use the information in the registry
with the tag syntax to choose, form, and process language tags. with the tag syntax to choose, form, and process language tags.
4.1. Choice of Language Tag 4.1. Choice of Language Tag
One is sometimes faced with the choice between several possible tags The guiding principle in forming language tags is to "tag content
for the same body of text. wisely." Sometimes there is a choice between several possible tags
for the same content. The choice of which tag to use depends on the
content and application in question, and some amount of judgment
might be necessary when selecting a tag.
Interoperability is best served when all users use the same language Interoperability is best served when the same language tag is used
tag in order to represent the same language. If an application has consistently to represent the same language. If an application has
requirements that make the rules here inapplicable, then that requirements that make the rules here inapplicable, then that
application risks damaging interoperability. It is strongly application risks damaging interoperability. It is strongly
RECOMMENDED that users not define their own rules for language tag RECOMMENDED that users not define their own rules for language tag
choice. choice.
Subtags SHOULD only be used where they add useful distinguishing Standards, protocols, and applications that reference this document
information; extraneous subtags interfere with the meaning, normatively but apply different rules to the ones given in this
understanding, and processing of language tags. In particular, users section MUST specify how language tag selection varies from the
and implementations SHOULD follow the 'Prefix' and 'Suppress-Script' guidelines given here.
fields in the registry (defined in Section 3.1): these fields provide
guidance on when specific additional subtags SHOULD (and SHOULD NOT)
be used in a language tag.
Of particular note, many applications can benefit from the use of To ensure consistent backward compatibility, this document contains
script subtags in language tags, as long as the use is consistent for several provisions to account for potential instability in the
a given context. Script subtags were not formally defined in RFC standards used to define the subtags that make up language tags.
3066 and their use can affect matching and subtag identification by
implementations of RFC 3066, as these subtags appear between the
primary language and region subtags. For example, if a user requests
content in an implementation of Section 2.5 of [RFC3066] using the
language range "en-US", content labeled "en-Latn-US" will not match
the request. Therefore, it is important to know when script subtags
will customarily be used and when they ought not be used. In the
registry, the Suppress-Script field helps ensure greater
compatibility between the language tags generated according to the
rules in this document and language tags and tag processors or
consumers based on RFC 3066 by defining when users SHOULD NOT include
a script subtag with a particular primary language subtag.
Extended language subtags (type 'extlang' in the registry; see These provisions mean that no valid language tag can become invalid,
Section 3.1) also appear between the primary language and region nor will a language tag have a narrower scope in the future (it may
subtags and are reserved for future standardization. Applications have a broader scope). The most appropriate language tag for a given
might benefit from their judicious use in forming language tags in application or content item might evolve over time, but once applied,
the future. Similar recommendations are expected to apply to their the tag itself cannot become invalid or have its meaning wholly
use as apply to script subtags. change.
Standards, protocols, and applications that reference this document A subtag SHOULD only be used when it adds useful distinguishing
normatively but apply different rules to the ones given in this information to the tag. Extraneous subtags interfere with the
section MUST specify how the procedure varies from the one given meaning, understanding, and processing of language tags. In
here. particular, users and implementations SHOULD follow the 'Prefix' and
'Suppress-Script' fields in the registry (defined in Section 3.1):
these fields provide guidance on when specific additional subtags
SHOULD be used or avoided in a language tag.
The choice of subtags used to form a language tag SHOULD be guided by The choice of subtags used to form a language tag SHOULD follow these
the following rules: guidelines:
1. Use as precise a tag as possible, but no more specific than is 1. Use as precise a tag as possible, but no more specific than is
justified. Avoid using subtags that are not important for justified. Avoid using subtags that are not important for
distinguishing content in an application. distinguishing content in an application.
* For example, 'de' might suffice for tagging an email written * For example, 'de' might suffice for tagging an email written
in German, while "de-CH-1996" is probably unnecessarily in German, while "de-CH-1996" is probably unnecessarily
precise for such a task. precise for such a task.
* Note that some subtag sequences might not represent the
language a casual user might expect. For example, the Swiss
German (Schweizerdeutsch) language is represented by "gsw-CH"
and not by "de-CH". This latter tag represents German ('de')
as used in Switzerland ('CH'), also known as Swiss High German
(Schweizer Hochdeutsch). Both are real languages, and
distinguishing between them could be important to an
application.
2. The script subtag SHOULD NOT be used to form language tags unless 2. The script subtag SHOULD NOT be used to form language tags unless
the script adds some distinguishing information to the tag. The the script adds some distinguishing information to the tag.
field 'Suppress-Script' in the primary language record in the Script subtags were first formally defined in [RFC4646]. Their
registry indicates which script subtags do not add distinguishing use can affect matching and subtag identification for
information for most applications. implementations of [RFC1766] or [RFC3066] (which are obsoleted by
this document), as these subtags appear between the primary
language and region subtags. Some applications can benefit from
the use of script subtags in language tags, as long as the use is
consistent for a given context. Script subtags are never
appropriate for unwritten content (such as audio recordings).
The field 'Suppress-Script' in the primary or extended language
record in the registry indicates script subtags that do not add
distinguishing information for most applications; this field
defines when users SHOULD NOT include a script subtag with a
particular primary language subtag.
* For example, the subtag 'Latn' should not be used with the For example, if an implementation selects content using Basic
primary language 'en' because nearly all English documents are Filtering [RFC4647] (originally described in Section 14.4 of
written in the Latin script and it adds no distinguishing [RFC2616]) and the user requested the language range "en-US",
information. However, if a document were written in English content labeled "en-Latn-US" will not match the request and thus
mixing Latin script with another script such as Braille not be selected. Therefore, it is important to know when script
('Brai'), then it might be appropriate to choose to indicate subtags will customarily be used and when they ought not be used.
both scripts to aid in content selection, such as the
application of a style sheet. For example:
* The subtag 'Latn' should not be used with the primary language
'en' because nearly all English documents are written in the
Latin script and it adds no distinguishing information.
However, if a document were written in English mixing Latin
script with another script such as Braille ('Brai'), then it
might be appropriate to choose to indicate both scripts to aid
in content selection, such as the application of a style
sheet.
* When labeling content that is unwritten (such as a recording
of human speech), the script subtag should not be used, even
if the language is customarily written in several scripts.
Thus, the subtitles to a movie might use the tag "uz-Arab"
(Uzbek, Arabic script), but the audio track for the same
language would be tagged simply "uz". (The tag "uz-Zxxx"
could also be used where content is not written, as the subtag
'Zxxx' represents the "Code for unwritten documents".)
3. If a tag or subtag has a 'Preferred-Value' field in its registry 3. If a tag or subtag has a 'Preferred-Value' field in its registry
entry, then the value of that field SHOULD be used to form the entry, then the value of that field SHOULD be used to form the
language tag in preference to the tag or subtag in which the language tag in preference to the tag or subtag in which the
preferred value appears. preferred value appears.
* For example, use 'he' for Hebrew in preference to 'iw'. * For example, use 'jbo' for Lojban in preference to the
grandfathered tag "art-lojban".
4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 4. Use subtags or sequences of subtags for individual languages in
used to label content, even if the language is unknown. Omitting preference to subtags for language collections. A "language
the language tag altogether is preferred to using a tag with a collection" is a group of languages that are descended from a
primary language subtag of 'und'. The 'und' subtag MAY be useful common ancestor, are spoken in the same geographical area, or are
for protocols that require a language tag to be provided. The otherwise related. Certain language collections are assigned
'und' subtag MAY also be useful when matching language tags in codes by [ISO639-5] (and some of these [ISO639-5] codes are also
certain situations. defined as collections in [ISO639-2]). These codes are included
as primary language subtags in the registry. Subtags for a
language collection in the registry have a 'Scope' field with a
value of 'collection'. A subtag for a language collection is
always preferred to less specific alternatives such as 'mul' and
'und' (see below), and a subtag representing a language
collection MAY be used when more specific language information is
not available. However, most users and implementations do not
know there is a relationship between the collection and its
individual languages. In addition, the relationship between the
individual languages in the collection is not well defined; in
particular, the languages are usually not mutually intelligible.
Since the subtags are different, a request for the collection
will typically only produce items tagged with the collection's
subtag, not items tagged with subtags for the individual
languages contained in the collection.
5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used * For example, collections are interpreted inclusively, so the
whenever the protocol allows the separate tags for multiple subtag 'gem' (Germanic languages) could, but SHOULD NOT, be
languages, as is the case for the Content-Language header in used with content that would be better tagged with "en"
HTTP. The 'mul' subtag conveys little useful information: (English), "de" (German), or "gsw" (Swiss German, Alemannic).
content in multiple languages SHOULD individually tag the While 'gem' collects all of these (and other) languages, most
languages where they appear or otherwise indicate the actual implementations will not match 'gem' to the individual
language in preference to the 'mul' subtag. languages; thus, using the subtag will not produce the desired
result.
6. The same variant subtag SHOULD NOT be used more than once within 5. [ISO639-2] has defined several codes included in the subtag
a language tag. registry that require additional care when choosing language
tags. In most of these cases, where omitting the language tag is
permitted, such omission is preferable to using these codes.
Language tags SHOULD NOT incorporate these subtags as a prefix,
unless the additional information conveys some value to the
application.
* For example, do not use "de-DE-1901-1901". * The 'mul' (Multiple) primary language subtag identifies
content in multiple languages. This subtag SHOULD NOT be used
when a list of languages or individual tags for each content
element can be used instead. For example, the 'Content-
Language' header [RFC3282] allows a list of languages to be
used, not just a single language tag.
To ensure consistent backward compatibility, this document contains * The 'und' (Undetermined) primary language subtag identifies
several provisions to account for potential instability in the linguistic content whose language is not determined. This
standards used to define the subtags that make up language tags. subtag SHOULD NOT be used unless a language tag is required
These provisions mean that no language tag created under the rules in and language information is not available or cannot be
this document will become obsolete. determined. Omitting the language tag (where permitted) is
preferred. The 'und' subtag might be useful for protocols
that require a language tag to be provided or where a primary
language subtag is required (such as in "und-Latn"). The
'und' subtag MAY also be useful when matching language tags in
certain situations.
* The 'zxx' (Non-Linguistic, Not Applicable) primary language
subtag identifies content for which a language classification
is inappropriate or does not apply. Some examples might
include instrumental or electronic music; sound recordings
consisting of nonverbal sounds; audiovisual materials with no
narration, dialog, printed titles, or subtitles; machine-
readable data files consisting of machine languages or
character codes; or programming source code.
* The 'mis' (Uncoded) primary language subtag identifies content
whose language is known but that does not currently have a
corresponding subtag. This subtag SHOULD NOT be used.
Because the addition of other codes in the future can render
its application invalid, it is inherently unstable and hence
incompatible with the stability goals of BCP 47. It is always
preferable to use other subtags: either 'und' or (with prior
agreement) private use subtags.
6. Use variant subtags sparingly and in the correct order. Most
variant subtags have one or more 'Prefix' fields in the registry
that express the list of subtags with which they are appropriate.
Variants SHOULD only be used with subtags that appear in one of
these 'Prefix' fields. If a variant lists a second variant in
one of its 'Prefix' fields, the first variant SHOULD appear
directly after the second variant in any language tag where both
occur. General purpose variants (those with no 'Prefix' fields
at all) SHOULD appear after any other variant subtags. Order any
remaining variants by placing the most significant subtag first.
If none of the subtags is more significant or no relationship can
be determined, alphabetize the subtags. Because variants are
very specialized, using many of them together generally makes the
tag so narrow as to override the additional precision gained.
Putting the subtags into another order interferes with
interoperability, as well as the overall interpretation of the
tag.
For example:
* The tag "en-scotland-fonipa" (English, Scottish dialect, IPA
phonetic transcription) is correctly ordered because
'scotland' has a 'Prefix' of "en", while 'fonipa' has no
'Prefix' field.
* The tag "sl-IT-rozaj-biske-1994" is correctly ordered: 'rozaj'
lists "sl" as its sole 'Prefix'; 'biske' lists "sl-rozaj" as
its sole 'Prefix'. The subtag '1994' has several prefixes,
including "sl-rozaj". However, it follows both 'rozaj' and
'biske' because one of its 'Prefix' fields is "sl-rozaj-
biske".
7. The grandfathered tag "i-default" (Default Language) was
originally registered according to [RFC1766] to meet the needs of
[RFC2277]. It is not used to indicate a specific language, but
rather to identify the condition or content used where the
language preferences of the user cannot be established. It
SHOULD NOT be used except as a means of labeling the default
content for applications or protocols that require default
language content to be labeled with that specific tag. It MAY
also be used by an application or protocol to identify when the
default language content is being returned.
4.1.1. Tagging Encompassed Languages
Some primary language records in the registry have a 'Macrolanguage'
field (Section 3.1.10) that contains a mapping from each "encompassed
language" to its macrolanguage. The 'Macrolanguage' mapping doesn't
define what the relationship between the encompassed language and its
macrolanguage is, nor does it define how languages encompassed by the
same macrolanguage are related to each other. Two different
languages encompassed by the same macrolanguage may differ from one
another more than, say, French and Spanish do.
A few specific macrolanguages, such as Chinese ('zh') and Arabic
('ar'), are handled differently. See Section 4.1.2.
The more specific encompassed language subtag SHOULD be used to form
the language tag, although either the macrolanguage's primary
language subtag or the encompassed language's subtag MAY be used.
This means, for example, tagging Plains Cree with 'crk' rather than
'cr' (Cree), and so forth.
Each macrolanguage subtag's scope, by definition, includes all of its
encompassed languages. Since the relationship between encompassed
languages varies, users cannot assume that the macrolanguage subtag
means any particular encompassed language, nor that any given pair of
encompassed languages are mutually intelligible or otherwise
interchangeable.
Applications MAY use macrolanguage information to improve matching or
language negotiation. For example, the information that 'sr'
(Serbian) and 'hr' (Croatian) share a macrolanguage expresses a
closer relation between those languages than between, say, 'sr'
(Serbian) and 'ma' (Macedonian). However, this relationship is not
guaranteed nor is it exclusive. For example, Romanian ('ro') and
Moldavian ('mo') do not share a macrolanguage, but are far more
closely related to each other than Cantonese ('yue') and Wu ('wuu'),
which do share a macrolanguage.
4.1.2. Using Extended Language Subtags
To accommodate language tag forms used prior to the adoption of this
document, language tags provide a special compatibility mechanism:
the extended language subtag. Selected languages have been provided
with both primary and extended language subtags. These include
macrolanguages, such as Malay ('ms') and Uzbek ('uz'), that have a
specific dominant variety that is generally synonymous with the
macrolanguage. Other languages, such as the Chinese ('zh') and
Arabic ('ar') macrolanguages and the various sign languages ('sgn'),
have traditionally used their primary language subtag, possibly
coupled with various region subtags or as part of a registered
grandfathered tag, to indicate the language.
With the adoption of this document, specific ISO 639-3 subtags became
available to identify the languages contained within these diverse
language families or groupings. This presents a choice of language
tags where previously none existed:
o Each encompassed language's subtag SHOULD be used as the primary
language subtag. For example, a document in Mandarin Chinese
would be tagged "cmn" (the subtag for Mandarin Chinese) in
preference to "zh" (Chinese).
o If compatibility is desired or needed, the encompassed subtag MAY
be used as an extended language subtag. For example, a document
in Mandarin Chinese could be tagged "zh-cmn" instead of either
"cmn" or "zh".
o The macrolanguage or prefixing subtag MAY still be used to form
the tag instead of the more specific encompassed language subtag.
That is, tags such as "zh-HK" or "sgn-RU" are still valid.
Chinese ('zh') provides a useful illustration of this. In the past,
various content has used tags beginning with the 'zh' subtag, with
application-specific meaning being associated with region codes,
private use sequences, or grandfathered registered values. This is
because historically only the macrolanguage subtag 'zh' was available
for forming language tags. However, the languages encompassed by the
Chinese subtag 'zh' are, in the main, not mutually intelligible when
spoken, and the written forms of these languages also show wide
variation in form and usage.
To provide compatibility, Chinese languages encompassed by the 'zh'
subtag are in the registry both as primary language subtags and as
extended language subtags. For example, the ISO 639-3 code for
Cantonese is 'yue'. Content in Cantonese might historically have
used a tag such as "zh-HK" (since Cantonese is commonly spoken in
Hong Kong), although that tag actually means any type of Chinese as
used in Hong Kong. With the availability of ISO 639-3 codes in the
registry, content in Cantonese can be directly tagged using the 'yue'
subtag. The content can use it as a primary language subtag, as in
the tag "yue-HK" (Cantonese, Hong Kong). Or it can use an extended
language subtag with 'zh', as in the tag "zh-yue-Hant" (Chinese,
Cantonese, Traditional script).
As noted above, applications can choose to use the macrolanguage
subtag to form the tag instead of using the more specific encompassed
language subtag. For example, an application with large quantities
of data already using tags with the 'zh' (Chinese) subtag might
continue to use this more general subtag even for new data, even
though the content could be more precisely tagged with 'cmn'
(Mandarin), 'yue' (Cantonese), 'wuu' (Wu), and so on. Similarly, an
application already using tags that start with the 'ar' (Arabic)
subtag might continue to use this more general subtag even for new
data, which could be more precisely tagged with 'arb' (Standard
Arabic).
In some cases, the encompassed languages had tags registered for them
during the RFC 3066 era. Those grandfathered tags not already
deprecated or rendered redundant were deprecated in the registry upon
adoption of this document. As grandfathered values, they remain
valid for use, and some content or applications might use them. As
with other grandfathered tags, since implementations might not be
able to associate the grandfathered tags with the encompassed
language subtag equivalents that are recommended by this document,
implementations are encouraged to canonicalize tags for comparison
purposes. Some examples of this include the tags "zh-hakka" (Hakka)
and "zh-guoyu" (Mandarin or Standard Chinese).
Sign languages share a mode of communication rather than a linguistic
heritage. There are many sign languages that have developed
independently, and the subtag 'sgn' indicates only the presence of a
sign language. A number of sign languages also had grandfathered
tags registered for them during the RFC 3066 era. For example, the
grandfathered tag "sgn-US" was registered to represent 'American Sign
Language' specifically, without reference to the United States. This
is still valid, but deprecated: a document in American Sign Language
can be labeled either "ase" or "sgn-ase" (the 'ase' subtag is for the
language called 'American Sign Language').
4.2. Meaning of the Language Tag 4.2. Meaning of the Language Tag
The relationship between the tag and the information it relates to is The meaning of a language tag is related to the meaning of the
defined by the context in which the tag appears. Accordingly, this subtags that it contains. Each subtag, in turn, implies a certain
section gives only possible examples of its usage. range of expectations one might have for related content, although it
is not a guarantee. For example, the use of a script subtag such as
'Arab' (Arabic script) does not mean that the content contains only
Arabic characters. It does mean that the language involved is
predominantly in the Arabic script. Thus, a language tag and its
subtags can encompass a very wide range of variation and yet remain
appropriate in each particular instance.
Validity of a tag is not the only factor determining its usefulness.
While every valid tag has a meaning, it might not represent any real-
world language usage. This is unavoidable in a system in which
subtags can be combined freely. For example, tags such as
"ar-Cyrl-CO" (Arabic, Cyrillic script, as used in Colombia) or "tlh-
Kore-AQ-fonipa" (Klingon, Korean script, as used in Antarctica, IPA
phonetic transcription) are both valid and unlikely to represent a
useful combination of language attributes.
The meaning of a given tag doesn't depend on the context in which it
appears. The relationship between a tag's meaning and the
information objects to which that tag is applied, however, can vary.
o For a single information object, the associated language tags o For a single information object, the associated language tags
might be interpreted as the set of languages that is necessary for might be interpreted as the set of languages that is necessary for
a complete comprehension of the complete object. Example: Plain a complete comprehension of the complete object. Example: Plain
text documents. text documents.
o For an aggregation of information objects, the associated language o For an aggregation of information objects, the associated language
tags could be taken as the set of languages used inside components tags could be taken as the set of languages used inside components
of that aggregation. Examples: Document stores and libraries. of that aggregation. Examples: Document stores and libraries.
o For information objects whose purpose is to provide alternatives, o For information objects whose purpose is to provide alternatives,
the associated language tags could be regarded as a hint that the the associated language tags could be regarded as a hint that the
content is provided in several languages and that one has to content is provided in several languages and that one has to
inspect each of the alternatives in order to find its language or inspect each of the alternatives in order to find its language or
languages. In this case, the presence of multiple tags might not languages. In this case, the presence of multiple tags might not
mean that one needs to be multi-lingual to get complete mean that one needs to be multilingual to get complete
understanding of the document. Example: MIME multipart/ understanding of the document. Example: MIME multipart/
alternative. alternative [RFC2046].
o In markup languages, such as HTML and XML, language information o For markup languages, such as HTML and XML, language information
can be added to each part of the document identified by the markup can be added to each part of the document identified by the markup
structure (including the whole document itself). For example, one structure (including the whole document itself). For example, one
could write <span lang="fr">C'est la vie.</span> inside a could write <span lang="fr">C'est la vie.</span> inside a German
Norwegian document; the Norwegian-speaking user could then access document; the German-speaking user could then access a French-
a French-Norwegian dictionary to find out what the marked section German dictionary to find out what the marked section meant. If
meant. If the user were listening to that document through a the user were listening to that document through a speech
speech synthesis interface, this formation could be used to signal synthesis interface, this formation could be used to signal the
the synthesizer to appropriately apply French text-to-speech synthesizer to appropriately apply French text-to-speech
pronunciation rules to that span of text, instead of applying the pronunciation rules to that span of text, instead of applying the
inappropriate Norwegian rules. inappropriate German rules.
o For markup languages and document formats that allow the audience
to be identified, a language tag could indicate the audience(s)
appropriate for that document. For example, the same HTML
document described in the preceding bullet might have an HTTP
header "Content-Language: de" to indicate that the intended
audience for the file is German (even though three words appear
and are identified as being in French within it).
o For systems and APIs, language tags form the basis for most
implementations of locale identifiers. For example, see Unicode's
CLDR (Common Locale Data Repository) (see UTS #35 [UTS35])
project.
Language tags are related when they contain a similar sequence of Language tags are related when they contain a similar sequence of
subtags. For example, if a language tag B contains language tag A as subtags. For example, if a language tag B contains language tag A as
a prefix, then B is typically "narrower" or "more specific" than A. a prefix, then B is typically "narrower" or "more specific" than A.
Thus, "zh-Hant-TW" is more specific than "zh-Hant". Thus, "zh-Hant-TW" is more specific than "zh-Hant".
This relationship is not guaranteed in all cases: specifically, This relationship is not guaranteed in all cases: specifically,
languages that begin with the same sequence of subtags are NOT languages that begin with the same sequence of subtags are NOT
guaranteed to be mutually intelligible, although they might be. For guaranteed to be mutually intelligible, although they might be. For
example, the tag "az" shares a prefix with both "az-Latn" example, the tag "az" shares a prefix with both "az-Latn"
(Azerbaijani written using the Latin script) and "az-Cyrl" (Azerbaijani written using the Latin script) and "az-Cyrl"
(Azerbaijani written using the Cyrillic script). A person fluent in (Azerbaijani written using the Cyrillic script). A person fluent in
one script might not be able to read the other, even though the text one script might not be able to read the other, even though the
might be identical. Content tagged as "az" most probably is written linguistic content (e.g., what would be heard if both texts were read
in just one script and thus might not be intelligible to a reader aloud) might be identical. Content tagged as "az" most probably is
familiar with the other script. written in just one script and thus might not be intelligible to a
reader familiar with the other script.
4.3. Length Considerations Similarly, not all subtags specify an actual distinction in language.
For example, the tags "en-US" and "en-CA" mean, roughly, English with
features generally thought to be characteristic of the United States
and Canada, respectively. They do not imply that a significant
dialectical boundary exists between any arbitrarily selected point in
the United States and any arbitrarily selected point in Canada.
Neither does a particular region subtag imply that linguistic
distinctions do not exist within that region.
[RFC3066] did not provide an upper limit on the size of language 4.3. Lists of Languages
tags. While RFC 3066 did define the semantics of particular subtags
in such a way that most language tags consisted of language and In some applications, a single content item might best be associated
region subtags with a combined total length of up to six characters, with more than one language tag. Examples of such a usage include:
larger registered tags were not only possible but were actually
registered. o Content items that contain multiple, distinct varieties. Often
this is used to indicate an appropriate audience for a given
content item when multiple choices might be appropriate. Examples
of this could include:
* Metadata about the appropriate audience for a movie title. For
example, a DVD might label its individual audio tracks 'de'
(German), 'fr' (French), and 'es' (Spanish), but the overall
title would list "de, fr, es" as its overall audience.
* A French/English, English/French dictionary tagged as both "en"
and "fr" to specify that it applies equally to French and
English.
* A side-by-side or interlinear translation of a document, as is
commonly done with classical works in Latin or Greek.
o Content items that contain a single language but that require
multiple levels of specificity. For example, a library might wish
to classify a particular work as both Norwegian ('no') and as
Nynorsk ('nn') for audiences capable of appreciating the
distinction or needing to select content more narrowly.
4.4. Length Considerations
There is no defined upper limit on the size of language tags. While
historically most language tags have consisted of language and region
subtags with a combined total length of up to six characters, larger
tags have always been both possible and have actually appeared in
use.
Neither the language tag syntax nor other requirements in this Neither the language tag syntax nor other requirements in this
document impose a fixed upper limit on the number of subtags in a document impose a fixed upper limit on the number of subtags in a
language tag (and thus an upper bound on the size of a tag). The language tag (and thus an upper bound on the size of a tag). The
language tag syntax suggests that, depending on the specific language tag syntax suggests that, depending on the specific
language, more subtags (and thus a longer tag) are sometimes language, more subtags (and thus a longer tag) are sometimes
necessary to completely identify the language for certain necessary to completely identify the language for certain
applications; thus, it is possible to envision long or complex subtag applications; thus, it is possible to envision long or complex subtag
sequences. sequences.
4.3.1. Working with Limited Buffer Sizes 4.4.1. Working with Limited Buffer Sizes
Some applications and protocols are forced to allocate fixed buffer Some applications and protocols are forced to allocate fixed buffer
sizes or otherwise limit the length of a language tag. A conformant sizes or otherwise limit the length of a language tag. A conformant
implementation or specification MAY refuse to support the storage of implementation or specification MAY refuse to support the storage of
language tags that exceed a specified length. Any such limitation language tags that exceed a specified length. Any such limitation
SHOULD be clearly documented, and such documentation SHOULD include SHOULD be clearly documented, and such documentation SHOULD include
what happens to longer tags (for example, whether an error value is what happens to longer tags (for example, whether an error value is
generated or the language tag is truncated). A protocol that allows generated or the language tag is truncated). A protocol that allows
tags to be truncated at an arbitrary limit, without giving any tags to be truncated at an arbitrary limit, without giving any
indication of what that limit is, has the potential for causing harm indication of what that limit is, has the potential to cause harm by
by changing the meaning of tags in substantial ways. changing the meaning of tags in substantial ways.
In practice, most language tags do not require more than a few In practice, most language tags do not require more than a few
subtags and will not approach reasonably sized buffer limitations; subtags and will not approach reasonably sized buffer limitations;
see Section 4.1. see Section 4.1.
Some specifications or protocols have limits on tag length but do not Some specifications or protocols have limits on tag length but do not
have a fixed length limitation. For example, [RFC2231] has no have a fixed length limitation. For example, [RFC2231] has no
explicit length limitation: the length available for the language tag explicit length limitation: the length available for the language tag
is constrained by the length of other header components (such as the is constrained by the length of other header components (such as the
charset's name) coupled with the 76-character limit in [RFC2047]. charset's name) coupled with the 76-character limit in [RFC2047].
skipping to change at page 42, line 45 skipping to change at page 64, line 45
protocol for storage or transmission. protocol for storage or transmission.
Implementations SHOULD warn the user when a tag is truncated since Implementations SHOULD warn the user when a tag is truncated since
truncation changes the semantic meaning of the tag. truncation changes the semantic meaning of the tag.
Implementations of protocols or specifications that are space Implementations of protocols or specifications that are space
constrained but do not have a fixed limit SHOULD use the longest constrained but do not have a fixed limit SHOULD use the longest
possible tag in preference to truncation. possible tag in preference to truncation.
Protocols or specifications that specify limited buffer sizes for Protocols or specifications that specify limited buffer sizes for
language tags MUST allow for language tags of up to 33 characters. language tags MUST allow for language tags of at least 35
characters. Note that [RFC4646] recommended a minimum field size
Protocols or specifications that specify limited buffer sizes for of 42 characters because it included all three elements of the
language tags SHOULD allow for language tags of at least 42 'extlang' production. Two of these are now permanently reserved,
characters. so a registered primary language subtag of the maximum length of 8
characters is now longer than the longest language-extlang
combination. Protocols or specifications that commonly use
extensions or private use subtags might wish to reserve or
recommend a longer "minimum buffer" size.
The following illustration shows how the 42-character recommendation The following illustration shows how the 35-character recommendation
was derived. The combination of language and extended language was derived:
subtags was chosen for future compatibility. At up to 15 characters,
this combination is longer than the longest possible primary language
subtag (8 characters):
language = 3 (ISO 639-2; ISO 639-1 requires 2) language = 8 ; longest allowed registered value
extlang1 = 4 (each subsequent subtag includes '-') ; longer than primary+extlang
extlang2 = 4 (unlikely: needs prefix="language-extlang1") ; which requires 7 characters
extlang3 = 4 (extremely unlikely) script = 5 ; if not suppressed: see Section 4.1
script = 5 (if not suppressed: see Section 4.1) region = 4 ; UN M.49 numeric region code
region = 4 (UN M.49; ISO 3166 requires 3) ; ISO 3166-1 codes require 3
variant1 = 9 (MUST have language as a prefix) variant1 = 9 ; needs 'language' as a prefix
variant2 = 9 (MUST have language-variant1 as a prefix) variant2 = 9 ; very rare, as it needs
; 'language-variant1' as a prefix
total = 42 characters total = 35 characters
Figure 7: Derivation of the Limit on Tag Length Figure 7: Derivation of the Limit on Tag Length
4.3.2. Truncation of Language Tags 4.4.2. Truncation of Language Tags
Truncation of a language tag alters the meaning of the tag, and thus Truncation of a language tag alters the meaning of the tag, and thus
SHOULD be avoided. However, truncation of language tags is sometimes SHOULD be avoided. However, truncation of language tags is sometimes
necessary due to limited buffer sizes. Such truncation MUST NOT necessary due to limited buffer sizes. Such truncation MUST NOT
permit a subtag to be chopped off in the middle or the formation of permit a subtag to be chopped off in the middle or the formation of
invalid tags (for example, one ending with the "-" character). invalid tags (for example, one ending with the "-" character).
This means that applications or protocols that truncate tags MUST do This means that applications or protocols that truncate tags MUST do
so by progressively removing subtags along with their preceding "-" so by progressively removing subtags along with their preceding "-"
from the right side of the language tag until the tag is short enough from the right side of the language tag until the tag is short enough
skipping to change at page 44, line 5 skipping to change at page 66, line 5
Tag to truncate: zh-Latn-CN-variant1-a-extend1-x-wadegile-private1 Tag to truncate: zh-Latn-CN-variant1-a-extend1-x-wadegile-private1
1. zh-Latn-CN-variant1-a-extend1-x-wadegile 1. zh-Latn-CN-variant1-a-extend1-x-wadegile
2. zh-Latn-CN-variant1-a-extend1 2. zh-Latn-CN-variant1-a-extend1
3. zh-Latn-CN-variant1 3. zh-Latn-CN-variant1
4. zh-Latn-CN 4. zh-Latn-CN
5. zh-Latn 5. zh-Latn
6. zh 6. zh
Figure 8: Example of Tag Truncation Figure 8: Example of Tag Truncation
4.4. Canonicalization of Language Tags 4.5. Canonicalization of Language Tags
Since a particular language tag is sometimes used by many processes, Since a particular language tag can be used by many processes,
language tags SHOULD always be created or generated in a canonical language tags SHOULD always be created or generated in canonical
form. form.
A language tag is in canonical form when: A language tag is in 'canonical form' when the tag is well-formed
according to the rules in Sections 2.1 and 2.2 and it has been
canonicalized by applying each of the following steps in order, using
data from the IANA registry (see Section 3.1):
1. The tag is well-formed according the rules in Section 2.1 and 1. Extension sequences are ordered into case-insensitive ASCII order
Section 2.2. by singleton subtag.
2. Subtags of type 'Region' that have a Preferred-Value mapping in * For example, the subtag sequence '-a-babble' comes before
the IANA registry (see Section 3.1) SHOULD be replaced with their '-b-warble'.
mapped value. Note: In rare cases, the mapped value will also
have a Preferred-Value.
3. Redundant or grandfathered tags that have a Preferred-Value 2. Redundant or grandfathered tags are replaced by their 'Preferred-
mapping in the IANA registry (see Section 3.1) MUST be replaced Value', if there is one.
with their mapped value. These items either are deprecated
mappings created before the adoption of this document (such as
the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are
the result of later registrations or additions to this document
(for example, "zh-guoyu" might be mapped to a language-extlang
combination such as "zh-cmn" by some future update of this
document).
4. Other subtags that have a Preferred-Value mapping in the IANA * The field-body of the 'Preferred-Value' for grandfathered and
registry (see Section 3.1) MUST be replaced with their mapped redundant tags is an "extended language range" [RFC4647] and
value. These items consist entirely of clerical corrections to might consist of more than one subtag.
ISO 639-1 in which the deprecated subtags have been maintained
for compatibility purposes.
5. If more than one extension subtag sequence exists, the extension * 'Preferred-Value' fields in the registry provide mappings from
sequences are ordered into case-insensitive ASCII order by deprecated tags to modern equivalents. Many of these were
singleton subtag. created before the adoption of this document (such as the
mapping of "no-nyn" to "nn" or "i-klingon" to "tlh"). Others
are the result of later registrations or additions to the
registry as permitted or required by this document (for
example, "zh-hakka" was deprecated in favor of the ISO 639-3
code 'hak' when this document was adopted).
Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 3. Subtags are replaced by their 'Preferred-Value', if there is one.
form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in For extlangs, the original primary language subtag is also
canonical form. replaced if there is a primary language subtag in the 'Preferred-
Value'.
Example: The language tag "en-BU" (English as used in Burma) is not * The field-body of the 'Preferred-Value' for extlangs is an
canonical because the 'BU' subtag has a canonical mapping to 'MM' "extended language range" and typically maps to a primary
(Myanmar), although the tag "en-BU" maintains its validity. language subtag. For example, the subtag sequence "zh-hak"
(Chinese, Hakka) is replaced with the subtag 'hak' (Hakka).
* Most of the non-extlang subtags are either Region subtags
where the country name or designation has changed or clerical
corrections to ISO 639-1.
The canonical form contains no 'extlang' subtags. There is an
alternate 'extlang form' that maintains or reinstates extlang
subtags. This form can be useful in environments where the presence
of the 'Prefix' subtag is considered beneficial in matching or
selection (see Section 4.1.2).
A language tag is in 'extlang form' when the tag is well-formed
according to the rules in Sections 2.1 and 2.2 and it has been
processed by applying each of the following two steps in order, using
data from the IANA registry:
1. The language tag is first transformed into canonical form, as
described above.
2. If the language tag starts with a primary language subtag that is
also an extlang subtag, then the language tag is prepended with
the extlang's 'Prefix'.
* For example, "hak-CN" (Hakka, China) has the primary language
subtag 'hak', which in turn has an 'extlang' record with a
'Prefix' 'zh' (Chinese). The extlang form is "zh-hak-CN"
(Chinese, Hakka, China).
* Note that Step 2 (prepending a prefix) can restore a subtag
that was removed by Step 1 (canonicalizing).
Example: The language tag "en-a-aaa-b-ccc-bbb-x-xyz" is in canonical
form, while "en-b-ccc-bbb-a-aaa-X-xyz" is well-formed and potentially
valid (extensions 'a' and 'b' are not defined as of the publication
of this document) but not in canonical form (the extensions are not
in alphabetical order).
Example: Although the tag "en-BU" (English as used in Burma)
maintains its validity, the language tag "en-BU" is not in canonical
form because the 'BU' subtag has a canonical mapping to 'MM'
(Myanmar).
Canonicalization of language tags does not imply anything about the Canonicalization of language tags does not imply anything about the
use of upper or lowercase letters when processing or comparing use of upper- or lowercase letters when processing or comparing
subtags (and as described in Section 2.1). All comparisons MUST be subtags (and as described in Section 2.1). All comparisons MUST be
performed in a case-insensitive manner. performed in a case-insensitive manner.
When performing canonicalization of language tags, processors MAY When performing canonicalization of language tags, processors MAY
regularize the case of the subtags (that is, this process is regularize the case of the subtags (that is, this process is
OPTIONAL), following the case used in the registry. Note that this OPTIONAL), following the case used in the registry (see
corresponds to the following casing rules: uppercase all non-initial Section 2.1.1).
two-letter subtags; titlecase all non-initial four-letter subtags;
lowercase everything else.
Note: Case folding of ASCII letters in certain locales, unless If more than one variant appears within a tag, processors MAY reorder
carefully handled, sometimes produces non-ASCII character values. the variants to obtain better matching behavior or more consistent
The Unicode Character Database file "SpecialCasing.txt" defines the presentation. Reordering of the variants SHOULD follow the
specific cases that are known to cause problems with this. In recommendations for variant ordering in Section 4.1.
particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is
uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE).
Implementers SHOULD specify a locale-neutral casing operation to
ensure that case folding of subtags does not produce this value,
which is illegal in language tags. For example, if one were to
uppercase the region subtag 'in' using Turkish locale rules, the
sequence U+0130 U+004E would result instead of the expected 'IN'.
Note: if the field 'Deprecated' appears in a registry record without If the field 'Deprecated' appears in a registry record without an
an accompanying 'Preferred-Value' field, then that tag or subtag is accompanying 'Preferred-Value' field, then that tag or subtag is
deprecated without a replacement. Validating processors SHOULD NOT deprecated without a replacement. These values are canonical when
generate tags that include these values, although the values are they appear in a language tag. However, tags that include these
canonical when they appear in a language tag. values SHOULD NOT be selected by users or generated by
implementations.
An extension MUST define any relationships that exist between the An extension MUST define any relationships that exist between the
various subtags in the extension and thus MAY define an alternate various subtags in the extension and thus MAY define an alternate
canonicalization scheme for the extension's subtags. Extensions MAY canonicalization scheme for the extension's subtags. Extensions MAY
define how the order of the extension's subtags are interpreted. For define how the order of the extension's subtags is interpreted. For
example, an extension could define that its subtags are in canonical example, an extension could define that its subtags are in canonical
order when the subtags are placed into ASCII order: that is, order when the subtags are placed into ASCII order: that is, "en-a-
"en-a-aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might
might define that the order of the subtags influences their semantic define that the order of the subtags influences their semantic
meaning (so that "en-b-ccc-bbb-aaa" has a different value from meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b-
"en-b-aaa-bbb-ccc"). However, extension specifications SHOULD be aaa-bbb-ccc"). However, extension specifications SHOULD be designed
designed so that they are tolerant of the typical processes described so that they are tolerant of the typical processes described in
in Section 3.7. Section 3.7.
4.5. Considerations for Private Use Subtags 4.6. Considerations for Private Use Subtags
Private use subtags, like all other subtags, MUST conform to the Private use subtags, like all other subtags, MUST conform to the
format and content constraints in the ABNF. Private use subtags have format and content constraints in the ABNF. Private use subtags have
no meaning outside the private agreement between the parties that no meaning outside the private agreement between the parties that
intend to use or exchange language tags that employ them. The same intend to use or exchange language tags that employ them. The same
subtags MAY be used with a different meaning under a separate private subtags MAY be used with a different meaning under a separate private
agreement. They SHOULD NOT be used where alternatives exist and agreement. They SHOULD NOT be used where alternatives exist and
SHOULD NOT be used in content or protocols intended for general use. SHOULD NOT be used in content or protocols intended for general use.
Private use subtags are simply useless for information exchange Private use subtags are simply useless for information exchange
without prior arrangement. The value and semantic meaning of private without prior arrangement. The value and semantic meaning of private
use tags and of the subtags used within such a language tag are not use tags and of the subtags used within such a language tag are not
defined by this document. defined by this document.
Subtags defined in the IANA registry as having a specific private use Private use sequences introduced by the 'x' singleton are completely
meaning convey more information that a purely private use tag opaque to users or implementations outside of the private use
prefixed by the singleton subtag 'x'. For applications, this agreement. So, in addition to private use subtag sequences
additional information MAY be useful. introduced by the singleton subtag 'x', the Language Subtag Registry
provides private use language, script, and region subtags derived
from the private use codes assigned by the underlying standards.
These subtags are valid for use in forming language tags; they are
RECOMMENDED over the 'x' singleton private use subtag sequences
because they convey more information via their linkage to the
language tag's inherent structure.
For example, the region subtags 'AA', 'ZZ', and in the ranges For example, the region subtags 'AA', 'ZZ', and those in the ranges
'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) MAY 'QM'-'QZ' and 'XA'-'XZ' (derived from the ISO 3166-1 private use
be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a codes) can be used to form a language tag. A tag such as
great deal of public, interchangeable information about the language "zh-Hans-XQ" conveys a great deal of public, interchangeable
material (that it is Chinese in the simplified Chinese script and is information about the language material (that it is Chinese in the
suitable for some geographic region 'XQ'). While the precise simplified Chinese script and is suitable for some geographic region
geographic region is not known outside of private agreement, the tag 'XQ'). While the precise geographic region is not known outside of
conveys far more information than an opaque tag such as "x-someLang", private agreement, the tag conveys far more information than an
which contains no information about the language subtag or script opaque tag such as "x-somelang" or even "zh-Hans-x-xq" (where the
subtag outside of the private agreement. 'xq' subtag's meaning is entirely opaque).
However, in some cases content tagged with private use subtags MAY However, in some cases content tagged with private use subtags can
interact with other systems in a different and possibly unsuitable interact with other systems in a different and possibly unsuitable
manner compared to tags that use opaque, privately defined subtags, manner compared to tags that use opaque, privately defined subtags,
so the choice of the best approach sometimes depends on the so the choice of the best approach sometimes depends on the
particular domain in question. particular domain in question.
5. IANA Considerations 5. IANA Considerations
This section deals with the processes and requirements necessary for This section deals with the processes and requirements necessary for
IANA to undertake to maintain the subtag and extension registries as IANA to maintain the subtag and extension registries as defined by
defined by this document and in accordance with the requirements of this document and in accordance with the requirements of [RFC5226].
[RFC2434].
The impact on the IANA maintainers of the two registries defined by The impact on the IANA maintainers of the two registries defined by
this document will be a small increase in the frequency of new this document will be a small increase in the frequency of new
entries or updates. entries or updates. IANA also is required to create a new mailing
list (described below in Section 5.1) to announce registry changes
and updates.
5.1. Language Subtag Registry 5.1. Language Subtag Registry
Upon adoption of this document, the registry will be initialized by a IANA updated the registry using instructions and content provided in
companion document: [RFC4645]. The criteria and process for a companion document [RFC5645]. The criteria and process for
selecting the initial set of records are described in that document. selecting the updated set of records are described in that document.
The initial set of records represents no impact on IANA, since the The updated set of records represents no impact on IANA, since the
work to create it will be performed externally. work to create it will be performed externally.
The new registry MUST be listed under "Language Tags" at Future work on the Language Subtag Registry includes the following
<http://www.iana.org/numbers.html>, replacing the existing activities:
registrations defined by [RFC3066]. The existing set of registration
forms and RFC 3066 registrations MUST be relabeled as "Language Tags
(Obsolete)" and maintained (but not added to or modified).
Future work on the Language Subtag Registry SHALL be limited to o Inserting or replacing whole records. These records are
inserting or replacing whole records preformatted for IANA by the preformatted for IANA by the Language Subtag Reviewer, as
Language Subtag Reviewer as described in Section 3.3 of this document described in Section 3.3.
and archiving the forwarded registration form.
Each record MUST be sent to iana@iana.org with a subject line o Archiving and making publicly available the registration forms.
indicating whether the enclosed record is an insertion of a new
record (indicated by the word "INSERT" in the subject line) or a
replacement of an existing record (indicated by the word "MODIFY" in
the subject line). Records MUST NOT be deleted from the registry.
IANA MUST place any inserted or modified records into the appropriate
section of the language subtag registry, grouping the records by
their 'Type' field. Inserted records MAY be placed anywhere in the
appropriate section; there is no guarantee of the order of the
records beyond grouping them together by 'Type'. Modified records
MUST overwrite the record they replace.
Included in any request to insert or modify records MUST be a new o Announcing each updated version of the registry on the
File-Date record. This record MUST be placed first in the registry. "ietf-languages-announcements@iana.org" mailing list.
In the event that the File-Date record present in the registry has a
later date than the record being inserted or modified, the existing Each registration form sent to IANA contains a single record for
record MUST be preserved. incorporation into the registry. The form will be sent to
<iana@iana.org> by the Language Subtag Reviewer. It will have a
subject line indicating whether the enclosed form represents an
insertion of a new record (indicated by the word "INSERT" in the
subject line) or a replacement of an existing record (indicated by
the word "MODIFY" in the subject line). At no time can a record be
deleted from the registry.
IANA will extract the record from the form and place the inserted or
modified record into the appropriate section of the Language Subtag
Registry, grouping the records by their 'Type' field. Inserted
records can be placed anywhere within the appropriate section; there
is no guarantee that the registry's records will be placed in any
particular order except that they will always be grouped by 'Type'.
Modified records overwrite the record they replace.
Whenever an entry is created or modified in the registry, the 'File-
Date' record at the start of the registry is updated to reflect the
most recent modification date. The date format SHALL be the "full-
date" format of [RFC3339]. The date SHALL be the date on which that
version of the registry was first published by IANA. There SHALL be
at most one version of the registry published in a day. A 'File-
Date' record is also included in each request to IANA to insert or
modify records, indicating the acceptance date of the records in the
request.
The updated registry file MUST use the UTF-8 character encoding, and
IANA MUST check the registry file for proper encoding. Non-ASCII
characters can be sent to IANA by attaching the registration form to
the email message or by using various encodings in the mail message
body (UTF-8 is recommended). IANA will verify any unclear or
corrupted characters with the Language Subtag Reviewer prior to
posting the updated registry.
IANA will also archive and make publicly available from
http://www.iana.org each registration form. Note that multiple
registrations can pertain to the same record in the registry.
Developers who are dependent upon the Language Subtag Registry
sometimes would like to be informed of changes in the registry so
that they can update their implementations. When any change is made
to the Language Subtag Registry, IANA will send an announcement
message to <ietf-languages-announcements@iana.org> (a self-
subscribing list to which only IANA can post).
5.2. Extensions Registry 5.2. Extensions Registry
The Language Tag Extensions Registry will also be generated and sent The Language Tag Extensions Registry can contain at most 35 records,
to IANA as described in Section 3.7. This registry can contain at and thus changes to this registry are expected to be very infrequent.
most 35 records, and thus changes to this registry are expected to be
very infrequent.
Future work by IANA on the Language Tag Extensions Registry is Future work by IANA on the Language Tag Extensions Registry is
limited to two cases. First, the IESG MAY request that new records limited to two cases. First, the IESG MAY request that new records
be inserted into this registry from time to time. These requests be inserted into this registry from time to time. These requests
MUST include the record to insert in the exact format described in MUST include the record to insert in the exact format described in
Section 3.7. In addition, there MAY be occasional requests from the Section 3.7. In addition, there MAY be occasional requests from the
maintaining authority for a specific extension to update the contact maintaining authority for a specific extension to update the contact
information or URLs in the record. These requests MUST include the information or URLs in the record. These requests MUST include the
complete, updated record. IANA is not responsible for validating the complete, updated record. IANA is not responsible for validating the
information provided, only that it is properly formatted. It should information provided, only that it is properly formatted. IANA
reasonably be seen to come from the maintaining authority named in SHOULD take reasonable steps to ascertain that the request comes from
the record present in the registry. the maintaining authority named in the record present in the
registry.
6. Security Considerations 6. Security Considerations
Language tags used in content negotiation, like any other information Language tags used in content negotiation, like any other information
exchanged on the Internet, might be a source of concern because they exchanged on the Internet, might be a source of concern because they
might be used to infer the nationality of the sender, and thus might be used to infer the nationality of the sender, and thus
identify potential targets for surveillance. identify potential targets for surveillance.
This is a special case of the general problem that anything sent is This is a special case of the general problem that anything sent is
visible to the receiving party and possibly to third parties as well. visible to the receiving party and possibly to third parties as well.
skipping to change at page 48, line 32 skipping to change at page 71, line 50
no consequence whatsoever in determining whether that content might no consequence whatsoever in determining whether that content might
contain possible homographs. The fact that a text is tagged as being contain possible homographs. The fact that a text is tagged as being
in one language or using a particular script subtag provides no in one language or using a particular script subtag provides no
assurance whatsoever that it does not contain characters from scripts assurance whatsoever that it does not contain characters from scripts
other than the one(s) associated with or specified by that language other than the one(s) associated with or specified by that language
tag. tag.
Since there is no limit to the number of variant, private use, and Since there is no limit to the number of variant, private use, and
extension subtags, and consequently no limit on the possible length extension subtags, and consequently no limit on the possible length
of a tag, implementations need to guard against buffer overflow of a tag, implementations need to guard against buffer overflow
attacks. See Section 4.3 for details on language tag truncation, attacks. See Section 4.4 for details on language tag truncation,
which can occur as a consequence of defenses against buffer overflow. which can occur as a consequence of defenses against buffer overflow.
Although the specification of valid subtags for an extension (see To prevent denial-of-service attacks, applications SHOULD NOT depend
Section 3.7) MUST be available over the Internet, implementations on either the Language Subtag Registry or the Language Tag Extensions
SHOULD NOT mechanically depend on it being always accessible, to Registry being always accessible. Additionally, although the
prevent denial-of-service attacks. specification of valid subtags for an extension (see Section 3.7)
MUST be available over the Internet, implementations SHOULD NOT
mechanically depend on those sources being always accessible.
The registries specified in this document are not suitable for
frequent or real-time access to, or retrieval of, the full registry
contents. Most applications do not need registry data at all. For
others, being able to validate or canonicalize language tags as of a
particular registry date will be sufficient, as the registry contents
change only occasionally. Changes are announced to
<ietf-languages-announcements@iana.org>. This mailing list is
intended for interested organizations and individuals, not for bulk
subscription to trigger automatic software updates. The size of the
registry makes it unsuitable for automatic software updates.
Implementers considering integrating the Language Subtag Registry in
an automatic updating scheme are strongly advised to distribute only
suitably encoded differences, and only via their own infrastructure
-- not directly from IANA.
Changes, or the absence thereof, can also easily be detected by
looking at the 'File-Date' record at the start of the registry, or by
using features of the protocol used for downloading, without having
to download the full registry. At the time of publication of this
document, IANA is making the Language Tag Registry available over
HTTP 1.1. The proper way to update a local copy of the Language
Subtag Registry using HTTP 1.1 is to use a conditional GET [RFC2616].
7. Character Set Considerations 7. Character Set Considerations
The syntax in this document requires that language tags use only the The syntax in this document requires that language tags use only the
characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most
character sets, so the composition of language tags should not have character sets, so the composition of language tags shouldn't have
any character set issues. any character set issues.
Rendering of characters based on the content of a language tag is not The rendering of text based on the language tag is not addressed
addressed in this memo. Historically, some languages have relied on here. Historically, some processes have relied on the use of
the use of specific character sets or other information in order to character set/encoding information (or other external information) in
infer how a specific character should be rendered (notably this order to infer how a specific string of characters should be
applies to language- and culture-specific variations of Han rendered. Notably, this applies to language- and culture-specific
ideographs as used in Japanese, Chinese, and Korean). When language variations of Han ideographs as used in Japanese, Chinese, and
tags are applied to spans of text, rendering engines sometimes use Korean, where use of, for example, a Japanese character encoding such
that information in deciding which font to use in the absence of as EUC-JP implies that the text itself is in Japanese. When language
other information, particularly where languages with distinct writing tags are applied to spans of text, rendering engines might be able to
use that information to better select fonts or make other rendering
choices, particularly where languages with distinct writing
traditions use the same characters. traditions use the same characters.
8. Changes from RFC 3066 8. Changes from RFC 4646
The main goals for this revision of language tags were the following: The main goal for this revision of RFC 4646 was to incorporate two
new parts of ISO 639 (ISO 639-3 and ISO 639-5) and their attendant
sets of language codes into the IANA Language Subtag Registry. This
permits the identification of many more languages and language
collections than previously supported.
*Compatibility.* All RFC 3066 language tags (including those in the The specific changes in this document to meet these goals are:
IANA registry) remain valid in this specification. The changes in
this document represent additional constraints on language tags.
That is, in no case is the syntax more permissive and processors
based on the ABNF and other provisions of RFC 3066 (such as those
described in [XMLSchema]) will be able to process the tags described
by this document. In addition, this document defines language tags
in such as way as to ensure future compatibility.
*Stability.* Because of changes in the past in the underlying ISO o Defined the incorporation of ISO 639-3 and ISO 639-5 codes for use
standards, a valid RFC 3066 language tag could become invalid or have as primary and extended language subtags. It also permanently
its meaning change. This has the potential of invalidating content reserves and disallows the use of additional 'extlang' subtags.
that may have an extensive shelf-life. In this specification, once a The changes necessary to achieve this were:
language tag is valid, it remains valid forever.
*Validity.* The structure of language tags defined by this document * Modified the ABNF comments.
makes it possible to determine if a particular tag is well-formed
without regard for the actual content or "meaning" of the tag as a
whole. This is important because the registry grows and underlying
standards change over time. In addition, it must be possible to
determine if a tag is valid (or not) for a given point in time in
order to provide reproducible, testable results. This process must
not be error-prone; otherwise implementations might give different
results. By having an authoritative registry with specific
versioning information, the validity of language tags at any point in
time can be precisely determined (instead of interpolating values
from many separate sources).
*Utility.* It is sometimes important to be able to differentiate * Updated various registration and stability requirements
between written forms of a language -- for many implementations this sections to reference ISO 639-3 and ISO 639-5 in addition to
is more important than distinguishing between the spoken variants of ISO 639-1 and ISO 639-2.
a language. Languages are written in a wide variety of different
scripts, so this document provides for the generative use of ISO
15924 script codes. Like the generative use of ISO language and
country codes in RFC 3066, this allows combinations to be produced
without resorting to the registration process. The addition of UN
M.49 codes provides for the generation of language tags with regional
scope, which is also required by some applications.
The recast of the registry from containing whole language tags to * Edited the text to eliminate references to extended language
subtags is a key part of this. An important feature of RFC 3066 was subtags where they are no longer used.
that it allowed generative use of subtags. This allows people to
meaningfully use generated tags, without the delays in registering
whole tags or the need to register all of the combinations that might
be useful.
The choice of placing the extended language and script subtags * Explained the change in the section on extended language
between the primary language and region subtags was widely debated. subtags.
This design was chosen because the prevalent matching and content
negotiation schemes rely on the subtags being arranged in order of
increasing specificity. That is, the subtags that mark a greater
barrier to mutual intelligibility appear left-most in a tag. For
example, when selecting content written in Azerbaijani, the script
(Arabic, Cyrillic, or Latin) represents a greater barrier to
understanding than any regional variations (those associated with
Azerbaijan or Iran, for example). Individuals who prefer documents
in a particular script, but can deal with the minor regional
differences, can therefore select appropriate content. Applications
that do not deal with written content will continue to omit these
subtags.
*Extensibility.* Because of the widespread use of language tags, it o Changed the ABNF related to grandfathered tags. The irregular
is disruptive to have periodic revisions of the core specification, tags are now listed. Well-formed grandfathered tags are now
even in the face of demonstrated need. The extension mechanism described by the 'langtag' production, and the 'grandfathered'
provides for a way for independent RFCs to define extensions to production was removed as a result. Also: added description of
language tags. These extensions have a very constrained, well- both types of grandfathered tags to Section 2.2.8.
defined structure that prevents extensions from interfering with
implementations of language tags defined in this document.
The document also anticipates features of ISO 639-3 with the addition o Added the paragraph on "collections" to Section 4.1.
of the extended language subtags, as well as the possibility of other
ISO 639 parts becoming useful for the formation of language tags in
the future.
The use and definition of private use tags have also been modified, o Changed the capitalization rules for 'Tag' fields in Section 3.1.
to allow people to use private use subtags to extend or modify
defined tags and to move as much information as possible out of
private use and into the regular structure.
The goal for each of these modifications is to reduce or eliminate o Split Section 3.1 up into subsections.
the need for future revisions of this document.
The specific changes in this document to meet these goals are: o Modified Section 3.5 to allow 'Suppress-Script' fields to be
added, modified, or removed via the registration process. This
was an erratum from RFC 4646.
o Defines the ABNF and rules for subtags so that the category of all o Modified examples that used region code 'CS' (formerly Serbia and
subtags can be determined without reference to the registry. Montenegro) to use 'RS' (Serbia) instead.
o Adds the concept of well-formed vs. validating processors, o Modified the rules for creating and maintaining record
defining the rules by which an implementation can claim to be one 'Description' fields to prevent duplicates, including inverted
or the other. duplicates.
o Replaces the IANA language tag registry with a language subtag o Removed the lengthy description of why RFC 4646 was created from
registry that provides a complete list of valid subtags in the this section, which also caused the removal of the reference to
IANA registry. This allows for robust implementation and ease of XML Schema.
maintenance. The language subtag registry becomes the canonical
source for forming language tags.
o Provides a process that guarantees stability of language tags, by o Modified the text in Section 2.1 to place more emphasis on the
handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in fact that language tags are not case sensitive.
the event that they register a previously used value for a new
purpose.
o Allows ISO 15924 script code subtags and allows them to be used o Replaced the example "fr-Latn-CA" in Section 2.1 with "sr-Latn-RS"
generatively. Defines a method for indicating in the registry and "az-Arab-IR" because "fr-Latn-CA" doesn't respect the
when script subtags are necessary for a given language tag. 'Suppress-Script' on 'Latn' with 'fr'.
o Adds the concept of a variant subtag and allows variants to be o Changed the requirements for well-formedness to make singleton
used generatively. repetition checking optional (it is required for validity
checking) in Section 2.2.9.
o Adds the ability to use a class of UN M.49 tags for supra-national o Changed the text in Section 2.2.9 referring to grandfathered
regions and to resolve conflicts in the assignment of ISO 3166 checking to note that the list is now included in the ABNF.
codes.
o Defines the private use tags in ISO 639, ISO 15924, and ISO 3166 o Modified and added text to Section 3.2. The job description was
as the mechanism for creating private use language, script, and placed first. A note was added making clear that the Language
region subtags, respectively. Subtag Reviewer may delegate various non-critical duties,
including list moderation. Finally, additional text was added to
make the appointment process clear and to clarify that decisions
and performance of the reviewer are appealable.
o Adds a well-defined extension mechanism. o Added text to Section 3.5 clarifying that the
ietf-languages@iana.org list is operated by whomever the IESG
appoints.
o Defines an extended language subtag, possibly for use with certain o Added text to Section 3.1.5 clarifying that the first Description
anticipated features of ISO 639-3. in a 'language' record matches the corresponding Reference Name
for the language in ISO 639-3.
o Modified Section 2.2.9 to define classes of conformance related to
specific tags (formerly 'well-formed' and 'valid' referred to
implementations). Notes were added about the removal of 'extlang'
from the ABNF provided in RFC 4646, allowing for well-formedness
using this older definition. Reference to RFC 3066 well-
formedness was also added.
o Added text to the end of Section 3.1.2 noting that future versions
of this document might add new field types to the registry format
and recommending that implementations ignore any unrecognized
fields.
o Added text about what the lack of a 'Suppress-Script' field means
in a record to Section 3.1.9.
o Added text allowing the correction of misspellings and typographic
errors to Section 3.1.5.
o Added text to Section 3.1.8 disallowing 'Prefix' field conflicts
(such as circular prefix references).
o Modified text in Section 3.5 to require the subtag reviewer to
announce his/her decision (or extension) following the two-week
period. Also clarified that any decision or failure to decide can
be appealed.
o Modified text in Section 4.1 to include the (heretofore anecdotal)
guiding principle of tag choice, and clarifying the non-use of
script subtags in non-written applications.
o Prohibited multiple use of the same variant in a tag (i.e., "de-
1901-1901"). Previously, this was only a recommendation
("SHOULD").
o Removed inappropriate [RFC2119] language from the illustration in
Section 4.4.1.
o Replaced the example of deprecating "zh-guoyu" with "zh-
hakka"->"hak" in Section 4.5, noting that it was this document
that caused the change.
o Replaced the section in Section 4.1 dealing with "mul"/"und" to
include the subtags 'zxx' and 'mis', as well as the tag
"i-default". A normative reference to RFC 2277 was added.
o Added text to Section 3.5 clarifying that any modifications of a
registration request must be sent to the <ietf-languages@iana.org>
list before submission to IANA.
o Changed the ABNF for the record-jar format from using the LWSP
production to use a folding whitespace production similar to obs-
FWS in [RFC5234]. This effectively prevents unintentional blank
lines inside a field.
o Clarified and revised text in Sections 3.3, 3.5, and 5.1 to
clarify that the Language Subtag Reviewer sends the complete
registration forms to IANA, that IANA extracts the record from the
form, and that the forms must also be archived separately from the
registry.
o Added text to Section 5 requiring IANA to send an announcement to
an ietf-languages-announcements list whenever the registry is
updated.
o Modification of the registry to use UTF-8 as its character
encoding. This also entails additional instructions to IANA and
the Language Subtag Reviewer in the registration process.
o Modified the rules in Section 2.2.4 so that "exceptionally
reserved" ISO 3166-1 codes other than 'UK' were included into the
registry. In particular, this allows the code 'EU' (European
Union) to be used to form language tags or (more commonly) for
applications that use the registry for region codes to reference
this subtag.
o Modified the IANA considerations section (Section 5) to remove
unnecessary normative [RFC2119] language.
9. References 9. References
9.1. Normative References 9.1. Normative References
[ISO10646] International Organization for Standardization, [ISO15924] International Organization for Standardization, "ISO
"ISO/IEC 10646:2003. Information technology -- 15924:2004. Information and documentation -- Codes
Universal Multiple-Octet Coded Character Set (UCS)", for the representation of names of scripts",
2003. January 2004.
[ISO15924] International Organization for Standardization, "ISO [ISO3166-1] International Organization for Standardization, "ISO
15924:2004. Information and documentation -- Codes for 3166-1:2006. Codes for the representation of names
the representation of names of scripts", January 2004. of countries and their subdivisions -- Part 1:
Country codes", November 2006.
[ISO3166-1] International Organization for Standardization, "ISO [ISO639-1] International Organization for Standardization, "ISO
3166-1:1997. Codes for the representation of names of 639-1:2002. Codes for the representation of names
countries and their subdivisions -- Part 1: Country of languages -- Part 1: Alpha-2 code", July 2002.
codes", 1997.
[ISO639-1] International Organization for Standardization, "ISO [ISO639-2] International Organization for Standardization, "ISO
639-1:2002. Codes for the representation of names of 639-2:1998. Codes for the representation of names
languages -- Part 1: Alpha-2 code", 2002. of languages -- Part 2: Alpha-3 code", October 1998.
[ISO639-2] International Organization for Standardization, "ISO [ISO639-3] International Organization for Standardization, "ISO
639-2:1998. Codes for the representation of names of 639-3:2007. Codes for the representation of names
languages -- Part 2: Alpha-3 code, first edition", of languages - Part 3: Alpha-3 code for
1998. comprehensive coverage of languages", February 2007.
[ISO646] International Organization for Standardization, [ISO639-5] International Organization for Standardization, "ISO
"ISO/IEC 646:1991, Information technology -- ISO 7-bit 639-5:2008. Codes for the representation of names of
coded character set for information interchange.", languages -- Part 5: Alpha-3 code for language
1991. families and groups", May 2008.
[RFC2026] Bradner, S., "The Internet Standards Process -- [ISO646] International Organization for Standardization,
Revision 3", BCP 9, RFC 2026, October 1996. "ISO/IEC 646:1991, Information technology -- ISO
7-bit coded character set for information
interchange.", 1991.
[RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved [RFC2026] Bradner, S., "The Internet Standards Process --
in the IETF Standards Process", BCP 11, RFC 2028, Revision 3", BCP 9, RFC 2026, October 1996.
October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
an IANA Considerations Section in RFCs", BCP 26, Languages", BCP 18, RFC 2277, January 1998.
RFC 2434, October 1998.
[RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the
of Understanding Concerning the Technical Work of the Internet: Timestamps", RFC 3339, July 2002.
Internet Assigned Numbers Authority", RFC 2860,
June 2000.
[RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the [RFC4647] Phillips, A. and M. Davis, "Matching of Language
Internet: Timestamps", RFC 3339, July 2002. Tags", BCP 47, RFC 4647, September 2006.
[RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for
Syntax Specifications: ABNF", RFC 4234, October 2005. Writing an IANA Considerations Section in RFCs",
BCP 26, RFC 5226, May 2008.
[UN_M.49] Statistics Division, United Nations, "Standard Country [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for
or Area Codes for Statistical Use", UN Standard Syntax Specifications: ABNF", STD 68, RFC 5234,
Country or Area Codes for Statistical Use, Revision 4 January 2008.
(United Nations publication, Sales No. 98.XVII.9,
June 1999.
9.2. Informative References [SpecialCasing] The Unicode Consoritum, "Unicode Character Database,
Special Casing Properties", March 2008, <http://
unicode.org/Public/UNIDATA/SpecialCasing.txt>.
[RFC1766] Alvestrand, H., "Tags for the Identification of [UAX14] Freitag, A., "Unicode Standard Annex #14: Line
Languages", RFC 1766, March 1995. Breaking Properties", August 2006,
<http://www.unicode.org/reports/tr14/>.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail [UN_M.49] Statistics Division, United Nations, "Standard
Extensions) Part Three: Message Header Extensions for Country or Area Codes for Statistical Use", Revision
Non-ASCII Text", RFC 2047, November 1996. 4 (United Nations publication, Sales No. 98.XVII.9,
June 1999.
[RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and [Unicode] Unicode Consortium, "The Unicode Consortium. The
Encoded Word Extensions: Character Sets, Languages, Unicode Standard, Version 5.0, (Boston, MA, Addison-
and Continuations", RFC 2231, November 1997. Wesley, 2003. ISBN 0-321-49081-0)", January 2007.
[RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of 9.2. Informative References
ISO 10646", RFC 2781, February 2000.
[RFC3066] Alvestrand, H., "Tags for the Identification of [CLDR] "The Common Locale Data Repository Project",
Languages", BCP 47, RFC 3066, January 2001. <http://cldr.unicode.org>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing [RFC1766] Alvestrand, H., "Tags for the Identification of
RFC Text on Security Considerations", BCP 72, Languages", RFC 1766, March 1995.
RFC 3552, July 2003.
[RFC4645] Ewell, D., Ed., "Initial Language Subtag Registry", [RFC2028] Hovey, R. and S. Bradner, "The Organizations
RFC 4645, September 2006. Involved in the IETF Standards Process", BCP 11,
RFC 2028, October 1996.
[RFC4647] Phillips, A., Ed. and M. Davis, Ed., "Matching of [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet
Language Tags", BCP 47, RFC 4647, September 2006. Mail Extensions (MIME) Part Two: Media Types",
RFC 2046, November 1996.
[Unicode] Unicode Consortium, "The Unicode Standard, Version [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail
5.0", Boston, MA, Addison-Wesley, 2007. ISBN 0-321- Extensions) Part Three: Message Header Extensions
48091-0. for Non-ASCII Text", RFC 2047, November 1996.
[XML10] Bray (et al), T., "Extensible Markup Language (XML) [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and
1.0", 02 2004. Encoded Word Extensions:
Character Sets, Languages, and Continuations",
RFC 2231, November 1997.
[XMLSchema] Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
2: Datatypes Second Edition", 10 2004, < Masinter, L., Leach, P., and T. Berners-Lee,
http://www.w3.org/TR/xmlschema-2/>. "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616,
June 1999.
[iso639.prin] ISO 639 Joint Advisory Committee, "ISO 639 Joint [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of
Advisory Committee: Working principles for ISO 639 ISO 10646", RFC 2781, February 2000.
maintenance", March 2000, <http://www.loc.gov/
standards/iso639-2/iso639jac_n3r.html>.
[record-jar] Raymond, E., "The Art of Unix Programming", 2003, [RFC3066] Alvestrand, H., "Tags for the Identification of
<urn:isbn:0-13-142901-9>. Languages", RFC 3066, January 2001.
Appendix A. Acknowledgements [RFC3282] Alvestrand, H., "Content Language Headers",
RFC 3282, May 2002.
Any list of contributors is bound to be incomplete; please regard the [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing
following as only a selection from the group of people who have RFC Text on Security Considerations", BCP 72,
contributed to make this document what it is today. RFC 3552, July 2003.
The contributors to RFC 3066 and RFC 1766, the precursors of this [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
document, made enormous contributions directly or indirectly to this 10646", STD 63, RFC 3629, November 2003.
document and are generally responsible for the success of language
tags.
The following people (in alphabetical order) contributed to this [RFC4645] Ewell, D., "Initial Language Subtag Registry",
document or to RFCs 1766 and 3066: RFC 4645, September 2006.
Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, [RFC4646] Phillips, A. and M. Davis, "Tags for Identifying
Nathaniel Borenstein, Karen Broome, Eric Brunner, Sean M. Burke, M.T. Languages", BCP 47, RFC 4646, September 2006.
Carrasco Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter
Constable, John Cowan, Mark Crispin, Dave Crocker, Elwyn Davies,
Martin Duerst, Frank Ellerman, Michael Everson, Doug Ewell, Ned
Freed, Tim Goodwin, Dirk-Willem van Gulik, Marion Gunn, Joel Halpren,
Elliotte Rusty Harold, Paul Hoffman, Scott Hollenbeck, Richard
Ishida, Olle Jarnefors, Kent Karlsson, John Klensin, Erkki
Kolehmainen, Alain LaBonte, Eric Mader, Ira McDonald, Keith Moore,
Chris Newman, Masataka Ohta, Dylan Pierce, Randy Presuhn, George
Rhoten, Felix Sasaki, Markus Scherer, Keld Jorn Simonsen, Thierry
Sourbier, Otto Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha
Wolf, Francois Yergeau and many, many others.
Very special thanks must go to Harald Tveit Alvestrand, who [RFC5645] Ewell, D., Ed., "Update to the Language Subtag
originated RFCs 1766 and 3066, and without whom this document would Registry", September 2009.
not have been possible. Special thanks must go to Michael Everson,
who has served as Language Tag Reviewer for almost the complete
period since the publication of RFC 1766. Special thanks to Doug
Ewell, for his production of the first complete subtag registry, and
his work in producing a test parser for verifying language tags.
Appendix B. Examples of Language Tags (Informative) [UTS35] Davis, M., "Unicode Technical Standard #35: Locale
Data Markup Language (LDML)", December 2007,
<http://www.unicode.org/reports/tr35/>.
[iso639.prin] ISO 639 Joint Advisory Committee, "ISO 639 Joint
Advisory Committee: Working principles for ISO 639
maintenance", March 2000, <http://www.loc.gov/
standards/iso639-2/iso639jac_n3r.html>.
[record-jar] Raymond, E., "The Art of Unix Programming", 2003,
<urn:isbn:0-13-142901-9>.
Appendix A. Examples of Language Tags (Informative)
Simple language subtag: Simple language subtag:
de (German) de (German)
fr (French) fr (French)
ja (Japanese) ja (Japanese)
i-enochian (example of a grandfathered tag) i-enochian (example of a grandfathered tag)
skipping to change at page 56, line 27 skipping to change at page 80, line 27
Language subtag plus Script subtag: Language subtag plus Script subtag:
zh-Hant (Chinese written using the Traditional Chinese script) zh-Hant (Chinese written using the Traditional Chinese script)
zh-Hans (Chinese written using the Simplified Chinese script) zh-Hans (Chinese written using the Simplified Chinese script)
sr-Cyrl (Serbian written using the Cyrillic script) sr-Cyrl (Serbian written using the Cyrillic script)
sr-Latn (Serbian written using the Latin script) sr-Latn (Serbian written using the Latin script)
Extended language subtags and their primary language subtag
counterparts:
zh-cmn-Hans-CN (Chinese, Mandarin, Simplified script, as used in
China)
cmn-Hans-CN (Mandarin Chinese, Simplified script, as used in
China)
zh-yue-HK (Chinese, Cantonese, as used in Hong Kong SAR)
yue-HK (Cantonese Chinese, as used in Hong Kong SAR)
Language-Script-Region: Language-Script-Region:
zh-Hans-CN (Chinese written using the Simplified script as used in zh-Hans-CN (Chinese written using the Simplified script as used in
mainland China) mainland China)
sr-Latn-CS (Serbian written using the Latin script as used in sr-Latn-RS (Serbian written using the Latin script as used in
Serbia and Montenegro) Serbia)
Language-Variant: Language-Variant:
sl-rozaj (Resian dialect of Slovenian sl-rozaj (Resian dialect of Slovenian)
sl-rozaj-biske (San Giorgio dialect of Resian dialect of
Slovenian)
sl-nedis (Nadiza dialect of Slovenian) sl-nedis (Nadiza dialect of Slovenian)
Language-Region-Variant: Language-Region-Variant:
de-CH-1901 (German as used in Switzerland using the 1901 variant de-CH-1901 (German as used in Switzerland using the 1901 variant
[orthography]) [orthography])
sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect)
Language-Script-Region-Variant: Language-Script-Region-Variant:
sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the hy-Latn-IT-arevela (Eastern Armenian written in Latin script, as
Latin script as used in Italy. Note that this tag is NOT used in Italy)
RECOMMENDED because subtag 'sl' has a Suppress-Script value of
'Latn')
Language-Region: Language-Region:
de-DE (German for Germany) de-DE (German for Germany)
en-US (English as used in the United States) en-US (English as used in the United States)
es-419 (Spanish appropriate for the Latin America and Caribbean es-419 (Spanish appropriate for the Latin America and Caribbean
region using the UN region code) region using the UN region code)
Private use subtags: Private use subtags:
de-CH-x-phonebk de-CH-x-phonebk
az-Arab-x-AZE-derbend az-Arab-x-AZE-derbend
Extended language subtags (examples ONLY: extended languages MUST be
defined by revision or update to this document):
zh-min
zh-min-nan-Hant-CN
Private use registry values: Private use registry values:
x-whatever (private use using the singleton 'x') x-whatever (private use using the singleton 'x')
qaa-Qaaa-QM-x-southern (all private tags) qaa-Qaaa-QM-x-southern (all private tags)
de-Qaaa (German, with a private script) de-Qaaa (German, with a private script)
sr-Latn-QM (Serbian, Latin-script, private region) sr-Latn-QM (Serbian, Latin script, private region)
sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro) sr-Qaaa-RS (Serbian, private script, for Serbia)
Tags that use extensions (examples ONLY: extensions MUST be defined Tags that use extensions (examples ONLY -- extensions MUST be defined
by revision or update to this document or by RFC): by revision or update to this document, or by RFC):
en-US-u-islamCal en-US-u-islamcal
zh-CN-a-myExt-x-private zh-CN-a-myext-x-private
en-a-myExt-b-another
en-a-myext-b-another
Some Invalid Tags: Some Invalid Tags:
de-419-DE (two region tags) de-419-DE (two region tags)
a-DE (use of a single-character subtag in primary position; note a-DE (use of a single-character subtag in primary position; note
that there are a few grandfathered tags that start with "i-" that that there are a few grandfathered tags that start with "i-" that
are valid) are valid)
ar-a-aaa-b-bbb-a-ccc (two extensions with same single-letter ar-a-aaa-b-bbb-a-ccc (two extensions with same single-letter
prefix) prefix)
Authors' Addresses Appendix B. Examples of Registration Forms
Addison Phillips (Editor) LANGUAGE SUBTAG REGISTRATION FORM
Yahoo! Inc.
EMail: addison@inter-locale.com 1. Name of requester: Han Steenwijk
2. E-mail address of requester: han.steenwijk @ unipd.it
3. Record Requested:
Mark Davis (Editor) Type: variant
Google Subtag: biske
Description: The San Giorgio dialect of Resian
Description: The Bila dialect of Resian
Prefix: sl-rozaj
Comments: The dialect of San Giorgio/Bila is one of the
four major local dialects of Resian
EMail: mark.davis@macchiato.com or mark.davis@google.com 4. Intended meaning of the subtag:
Full Copyright Statement The local variety of Resian as spoken in San Giorgio/Bila
Copyright (C) The Internet Society (2006). 5. Reference to published description of the language (book or
article):
This document is subject to the rights, licenses and restrictions -- Jan I.N. Baudouin de Courtenay - Opyt fonetiki rez'janskich
contained in BCP 78, and except as set forth therein, the authors govorov, Varsava - Peterburg: Vende - Kozancikov, 1875.
retain all their rights.
This document and the information contained herein are provided on an LANGUAGE SUBTAG REGISTRATION FORM
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property 1. Name of requester: Jaska Zedlik
2. E-mail address of requester: jz53 @ zedlik.com
3. Record Requested:
The IETF takes no position regarding the validity or scope of any Type: variant
Intellectual Property Rights or other rights that might be claimed to Subtag: tarask
pertain to the implementation or use of the technology described in Description: Belarusian in Taraskievica orthography
this document or the extent to which any license under such rights Prefix: be
might or might not be available; nor does it represent that it has Comments: The subtag represents Branislau Taraskievic's Belarusian
made any independent effort to identify any such rights. Information orthography as published in "Bielaruski klasycny pravapis" by
on the procedures with respect to rights in RFC documents can be Juras Buslakou, Vincuk Viacorka, Zmicier Sanko, and Zmicier Sauka
found in BCP 78 and BCP 79. (Vilnia-Miensk 2005).
Copies of IPR disclosures made to the IETF Secretariat and any 4. Intended meaning of the subtag:
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The subtag is intended to represent the Belarusian orthography as
copyrights, patents or patent applications, or other proprietary published in "Bielaruski klasycny pravapis" by Juras Buslakou, Vincuk
rights that may cover technology that may be required to implement Viacorka, Zmicier Sanko, and Zmicier Sauka (Vilnia-Miensk 2005).
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgement 5. Reference to published description of the language (book or
article):
Funding for the RFC Editor function is provided by the IETF Taraskievic, Branislau. Bielaruskaja gramatyka dla skol. Vilnia: Vyd.
Administrative Support Activity (IASA). "Bielaruskaha kamitetu", 1929, 5th edition.
Buslakou, Juras; Viacorka, Vincuk; Sanko, Zmicier; Sauka, Zmicier.
Bielaruski klasycny pravapis. Vilnia-Miensk, 2005.
6. Any other relevant information:
Belarusian in Taraskievica orthography became widely used, especially
in Belarusian-speaking Internet segment, but besides this some books
and newspapers are also printed using this orthography of Belarusian.
Appendix C. Acknowledgements
Any list of contributors is bound to be incomplete; please regard the
following as only a selection from the group of people who have
contributed to make this document what it is today.
The contributors to RFC 4646, RFC 4647, RFC 3066, and RFC 1766, the
precursors of this document, made enormous contributions directly or
indirectly to this document and are generally responsible for the
success of language tags.
The following people contributed to this document:
Stephane Bortzmeyer, Karen Broome, Peter Constable, John Cowan,
Martin Duerst, Frank Ellerman, Doug Ewell, Deborah Garside, Marion
Gunn, Alfred Hoenes, Kent Karlsson, Chris Newman, Randy Presuhn,
Stephen Silver, Shawn Steele, and many, many others.
Very special thanks must go to Harald Tveit Alvestrand, who
originated RFCs 1766 and 3066, and without whom this document would
not have been possible.
Special thanks go to Michael Everson, who served as the Language Tag
Reviewer for almost the entire RFC 1766/RFC 3066 period, as well as
the Language Subtag Reviewer since the adoption of RFC 4646.
Special thanks also go to Doug Ewell, for his production of the first
complete subtag registry, his work to support and maintain new
registrations, and his careful editorship of both RFC 4645 and
[RFC5645].
Authors' Addresses
Addison Phillips (editor)
Lab126
EMail: addison@inter-locale.com
URI: http://www.inter-locale.com
Mark Davis (editor)
Google
EMail: markdavis@google.com
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