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HTTPbis Working Group R. Fielding, Ed.
Internet-Draft Day Software
Obsoletes: 2616 (if approved) J. Gettys
Updates: 2817 (if approved) Alcatel-Lucent
Intended status: Standards Track J. Mogul
Expires: February 5, 2011 HP
H. Frystyk
Microsoft
L. Masinter
Adobe Systems
P. Leach
Microsoft
T. Berners-Lee
W3C/MIT
Y. Lafon, Ed.
W3C
J. Reschke, Ed.
greenbytes
August 4, 2010
HTTP/1.1, part 2: Message Semantics
draft-ietf-httpbis-p2-semantics-11
Abstract
The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypermedia information
systems. HTTP has been in use by the World Wide Web global
information initiative since 1990. This document is Part 2 of the
seven-part specification that defines the protocol referred to as
"HTTP/1.1" and, taken together, obsoletes RFC 2616. Part 2 defines
the semantics of HTTP messages as expressed by request methods,
request-header fields, response status codes, and response-header
fields.
Editorial Note (To be removed by RFC Editor)
Discussion of this draft should take place on the HTTPBIS working
group mailing list (ietf-http-wg@w3.org). The current issues list is
at <http://tools.ietf.org/wg/httpbis/trac/report/3> and related
documents (including fancy diffs) can be found at
<http://tools.ietf.org/wg/httpbis/>.
The changes in this draft are summarized in Appendix C.12.
Status of This Memo
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This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 5, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Contributions published or made publicly available before November
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than English.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 6
1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 6
1.2.1. Core Rules . . . . . . . . . . . . . . . . . . . . . . 7
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1.2.2. ABNF Rules defined in other Parts of the
Specification . . . . . . . . . . . . . . . . . . . . 7
2. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Method Registry . . . . . . . . . . . . . . . . . . . . . 8
3. Request Header Fields . . . . . . . . . . . . . . . . . . . . 9
4. Status Code and Reason Phrase . . . . . . . . . . . . . . . . 10
4.1. Status Code Registry . . . . . . . . . . . . . . . . . . . 12
5. Response Header Fields . . . . . . . . . . . . . . . . . . . . 12
6. Representation . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Identifying the Resource Associated with a
Representation . . . . . . . . . . . . . . . . . . . . . . 13
7. Method Definitions . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Safe and Idempotent Methods . . . . . . . . . . . . . . . 14
7.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . . 14
7.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . . 14
7.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.4. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.5. POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.6. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.8. TRACE . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.9. CONNECT . . . . . . . . . . . . . . . . . . . . . . . . . 20
8. Status Code Definitions . . . . . . . . . . . . . . . . . . . 20
8.1. Informational 1xx . . . . . . . . . . . . . . . . . . . . 20
8.1.1. 100 Continue . . . . . . . . . . . . . . . . . . . . . 20
8.1.2. 101 Switching Protocols . . . . . . . . . . . . . . . 21
8.2. Successful 2xx . . . . . . . . . . . . . . . . . . . . . . 21
8.2.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . . 21
8.2.2. 201 Created . . . . . . . . . . . . . . . . . . . . . 21
8.2.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . . 22
8.2.4. 203 Non-Authoritative Information . . . . . . . . . . 22
8.2.5. 204 No Content . . . . . . . . . . . . . . . . . . . . 22
8.2.6. 205 Reset Content . . . . . . . . . . . . . . . . . . 23
8.2.7. 206 Partial Content . . . . . . . . . . . . . . . . . 23
8.3. Redirection 3xx . . . . . . . . . . . . . . . . . . . . . 23
8.3.1. 300 Multiple Choices . . . . . . . . . . . . . . . . . 24
8.3.2. 301 Moved Permanently . . . . . . . . . . . . . . . . 24
8.3.3. 302 Found . . . . . . . . . . . . . . . . . . . . . . 25
8.3.4. 303 See Other . . . . . . . . . . . . . . . . . . . . 25
8.3.5. 304 Not Modified . . . . . . . . . . . . . . . . . . . 26
8.3.6. 305 Use Proxy . . . . . . . . . . . . . . . . . . . . 26
8.3.7. 306 (Unused) . . . . . . . . . . . . . . . . . . . . . 26
8.3.8. 307 Temporary Redirect . . . . . . . . . . . . . . . . 26
8.4. Client Error 4xx . . . . . . . . . . . . . . . . . . . . . 27
8.4.1. 400 Bad Request . . . . . . . . . . . . . . . . . . . 27
8.4.2. 401 Unauthorized . . . . . . . . . . . . . . . . . . . 27
8.4.3. 402 Payment Required . . . . . . . . . . . . . . . . . 27
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8.4.4. 403 Forbidden . . . . . . . . . . . . . . . . . . . . 27
8.4.5. 404 Not Found . . . . . . . . . . . . . . . . . . . . 28
8.4.6. 405 Method Not Allowed . . . . . . . . . . . . . . . . 28
8.4.7. 406 Not Acceptable . . . . . . . . . . . . . . . . . . 28
8.4.8. 407 Proxy Authentication Required . . . . . . . . . . 28
8.4.9. 408 Request Timeout . . . . . . . . . . . . . . . . . 29
8.4.10. 409 Conflict . . . . . . . . . . . . . . . . . . . . . 29
8.4.11. 410 Gone . . . . . . . . . . . . . . . . . . . . . . . 29
8.4.12. 411 Length Required . . . . . . . . . . . . . . . . . 30
8.4.13. 412 Precondition Failed . . . . . . . . . . . . . . . 30
8.4.14. 413 Request Entity Too Large . . . . . . . . . . . . . 30
8.4.15. 414 URI Too Long . . . . . . . . . . . . . . . . . . . 30
8.4.16. 415 Unsupported Media Type . . . . . . . . . . . . . . 30
8.4.17. 416 Requested Range Not Satisfiable . . . . . . . . . 30
8.4.18. 417 Expectation Failed . . . . . . . . . . . . . . . . 31
8.5. Server Error 5xx . . . . . . . . . . . . . . . . . . . . . 31
8.5.1. 500 Internal Server Error . . . . . . . . . . . . . . 31
8.5.2. 501 Not Implemented . . . . . . . . . . . . . . . . . 31
8.5.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . . 31
8.5.4. 503 Service Unavailable . . . . . . . . . . . . . . . 31
8.5.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . . 32
8.5.6. 505 HTTP Version Not Supported . . . . . . . . . . . . 32
9. Header Field Definitions . . . . . . . . . . . . . . . . . . . 32
9.1. Allow . . . . . . . . . . . . . . . . . . . . . . . . . . 32
9.2. Expect . . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.3. From . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.4. Location . . . . . . . . . . . . . . . . . . . . . . . . . 34
9.5. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . . 35
9.6. Referer . . . . . . . . . . . . . . . . . . . . . . . . . 36
9.7. Retry-After . . . . . . . . . . . . . . . . . . . . . . . 36
9.8. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 37
9.9. User-Agent . . . . . . . . . . . . . . . . . . . . . . . . 37
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38
10.1. Method Registry . . . . . . . . . . . . . . . . . . . . . 38
10.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 38
10.3. Header Field Registration . . . . . . . . . . . . . . . . 39
11. Security Considerations . . . . . . . . . . . . . . . . . . . 40
11.1. Transfer of Sensitive Information . . . . . . . . . . . . 40
11.2. Encoding Sensitive Information in URIs . . . . . . . . . . 41
11.3. Location Headers and Spoofing . . . . . . . . . . . . . . 42
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 42
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42
13.1. Normative References . . . . . . . . . . . . . . . . . . . 42
13.2. Informative References . . . . . . . . . . . . . . . . . . 43
Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 43
Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 44
Appendix C. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 47
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C.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 47
C.2. Since draft-ietf-httpbis-p2-semantics-00 . . . . . . . . . 47
C.3. Since draft-ietf-httpbis-p2-semantics-01 . . . . . . . . . 47
C.4. Since draft-ietf-httpbis-p2-semantics-02 . . . . . . . . . 48
C.5. Since draft-ietf-httpbis-p2-semantics-03 . . . . . . . . . 49
C.6. Since draft-ietf-httpbis-p2-semantics-04 . . . . . . . . . 49
C.7. Since draft-ietf-httpbis-p2-semantics-05 . . . . . . . . . 49
C.8. Since draft-ietf-httpbis-p2-semantics-06 . . . . . . . . . 50
C.9. Since draft-ietf-httpbis-p2-semantics-07 . . . . . . . . . 50
C.10. Since draft-ietf-httpbis-p2-semantics-08 . . . . . . . . . 51
C.11. Since draft-ietf-httpbis-p2-semantics-09 . . . . . . . . . 51
C.12. Since draft-ietf-httpbis-p2-semantics-10 . . . . . . . . . 51
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
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1. Introduction
This document defines HTTP/1.1 request and response semantics. Each
HTTP message, as defined in [Part1], is in the form of either a
request or a response. An HTTP server listens on a connection for
HTTP requests and responds to each request, in the order received on
that connection, with one or more HTTP response messages. This
document defines the commonly agreed upon semantics of the HTTP
uniform interface, the intentions defined by each request method, and
the various response messages that might be expected as a result of
applying that method to the target resource.
This document is currently disorganized in order to minimize the
changes between drafts and enable reviewers to see the smaller errata
changes. The next draft will reorganize the sections to better
reflect the content. In particular, the sections will be ordered
according to the typical processing of an HTTP request message (after
message parsing): resource mapping, general header fields, methods,
request modifiers, response status, and resource metadata. The
current mess reflects how widely dispersed these topics and
associated requirements had become in [RFC2616].
1.1. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
An implementation is not compliant if it fails to satisfy one or more
of the "MUST" or "REQUIRED" level requirements for the protocols it
implements. An implementation that satisfies all the "MUST" or
"REQUIRED" level and all the "SHOULD" level requirements for its
protocols is said to be "unconditionally compliant"; one that
satisfies all the "MUST" level requirements but not all the "SHOULD"
level requirements for its protocols is said to be "conditionally
compliant".
1.2. Syntax Notation
This specification uses the ABNF syntax defined in Section 1.2 of
[Part1] (which extends the syntax defined in [RFC5234] with a list
rule). Appendix B shows the collected ABNF, with the list rule
expanded.
The following core rules are included by reference, as defined in
[RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
(CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any 8-bit
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sequence of data), SP (space), VCHAR (any visible USASCII character),
and WSP (whitespace).
1.2.1. Core Rules
The core rules below are defined in Section 1.2.2 of [Part1]:
quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
token = <token, defined in [Part1], Section 1.2.2>
OWS = <OWS, defined in [Part1], Section 1.2.2>
RWS = <RWS, defined in [Part1], Section 1.2.2>
obs-text = <obs-text, defined in [Part1], Section 1.2.2>
1.2.2. ABNF Rules defined in other Parts of the Specification
The ABNF rules below are defined in other parts:
absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
comment = <comment, defined in [Part1], Section 3.2>
Host = <Host, defined in [Part1], Section 2.6>
HTTP-date = <HTTP-date, defined in [Part1], Section 6.1>
partial-URI = <partial-URI, defined in [Part1], Section 2.6>
product = <product, defined in [Part1], Section 6.3>
TE = <TE, defined in [Part1], Section 9.5>
URI-reference = <URI-reference, defined in [Part1], Section 2.6>
Accept = <Accept, defined in [Part3], Section 6.1>
Accept-Charset =
<Accept-Charset, defined in [Part3], Section 6.2>
Accept-Encoding =
<Accept-Encoding, defined in [Part3], Section 6.3>
Accept-Language =
<Accept-Language, defined in [Part3], Section 6.4>
ETag = <ETag, defined in [Part4], Section 6.1>
If-Match = <If-Match, defined in [Part4], Section 6.2>
If-Modified-Since =
<If-Modified-Since, defined in [Part4], Section 6.3>
If-None-Match = <If-None-Match, defined in [Part4], Section 6.4>
If-Unmodified-Since =
<If-Unmodified-Since, defined in [Part4], Section 6.5>
Accept-Ranges = <Accept-Ranges, defined in [Part5], Section 5.1>
If-Range = <If-Range, defined in [Part5], Section 5.3>
Range = <Range, defined in [Part5], Section 5.4>
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Age = <Age, defined in [Part6], Section 3.1>
Vary = <Vary, defined in [Part6], Section 3.5>
Authorization = <Authorization, defined in [Part7], Section 3.1>
Proxy-Authenticate =
<Proxy-Authenticate, defined in [Part7], Section 3.2>
Proxy-Authorization =
<Proxy-Authorization, defined in [Part7], Section 3.3>
WWW-Authenticate =
<WWW-Authenticate, defined in [Part7], Section 3.4>
2. Method
The Method token indicates the method to be performed on the target
resource (Section 4.3 of [Part1]). The method is case-sensitive.
Method = %x4F.50.54.49.4F.4E.53 ; "OPTIONS", Section 7.2
/ %x47.45.54 ; "GET", Section 7.3
/ %x48.45.41.44 ; "HEAD", Section 7.4
/ %x50.4F.53.54 ; "POST", Section 7.5
/ %x50.55.54 ; "PUT", Section 7.6
/ %x44.45.4C.45.54.45 ; "DELETE", Section 7.7
/ %x54.52.41.43.45 ; "TRACE", Section 7.8
/ %x43.4F.4E.4E.45.43.54 ; "CONNECT", Section 7.9
/ extension-method
extension-method = token
The list of methods allowed by a resource can be specified in an
Allow header field (Section 9.1). The status code of the response
always notifies the client whether a method is currently allowed on a
resource, since the set of allowed methods can change dynamically.
An origin server SHOULD respond with the status code 405 (Method Not
Allowed) if the method is known by the origin server but not allowed
for the resource, and 501 (Not Implemented) if the method is
unrecognized or not implemented by the origin server. The methods
GET and HEAD MUST be supported by all general-purpose servers. All
other methods are OPTIONAL; however, if the above methods are
implemented, they MUST be implemented with the same semantics as
those specified in Section 7.
2.1. Method Registry
The HTTP Method Registry defines the name space for the Method token
in the Request line of an HTTP request.
Registrations MUST include the following fields:
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o Method Name (see Section 2)
o Safe ("yes" or "no", see Section 7.1.1)
o Pointer to specification text
Values to be added to this name space are subject to IETF review
([RFC5226], Section 4.1).
The registry itself is maintained at
<http://www.iana.org/assignments/http-methods>.
3. Request Header Fields
The request-header fields allow the client to pass additional
information about the request, and about the client itself, to the
server. These fields act as request modifiers, with semantics
equivalent to the parameters on a programming language method
invocation.
request-header = Accept ; [Part3], Section 6.1
/ Accept-Charset ; [Part3], Section 6.2
/ Accept-Encoding ; [Part3], Section 6.3
/ Accept-Language ; [Part3], Section 6.4
/ Authorization ; [Part7], Section 3.1
/ Expect ; Section 9.2
/ From ; Section 9.3
/ Host ; [Part1], Section 9.4
/ If-Match ; [Part4], Section 6.2
/ If-Modified-Since ; [Part4], Section 6.3
/ If-None-Match ; [Part4], Section 6.4
/ If-Range ; [Part5], Section 5.3
/ If-Unmodified-Since ; [Part4], Section 6.5
/ Max-Forwards ; Section 9.5
/ Proxy-Authorization ; [Part7], Section 3.3
/ Range ; [Part5], Section 5.4
/ Referer ; Section 9.6
/ TE ; [Part1], Section 9.5
/ User-Agent ; Section 9.9
Request-header field names can be extended reliably only in
combination with a change in the protocol version. However, new or
experimental header fields MAY be given the semantics of request-
header fields if all parties in the communication recognize them to
be request-header fields.
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4. Status Code and Reason Phrase
The Status-Code element is a 3-digit integer result code of the
attempt to understand and satisfy the request. The status codes
listed below are defined in Section 8, Section 3 of [Part4], Section
3 of [Part5], and Section 2 of [Part7].
The Reason-Phrase is intended to give a short textual description of
the Status-Code. The Status-Code is intended for use by automata and
the Reason-Phrase is intended for the human user. The client is not
required to examine or display the Reason-Phrase.
The individual values of the numeric status codes defined for
HTTP/1.1, and an example set of corresponding Reason-Phrase values,
are presented below. The reason phrases listed here are only
recommendations -- they MAY be replaced by local equivalents without
affecting the protocol.
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Status-Code =
"100" ; Section 8.1.1: Continue
/ "101" ; Section 8.1.2: Switching Protocols
/ "200" ; Section 8.2.1: OK
/ "201" ; Section 8.2.2: Created
/ "202" ; Section 8.2.3: Accepted
/ "203" ; Section 8.2.4: Non-Authoritative Information
/ "204" ; Section 8.2.5: No Content
/ "205" ; Section 8.2.6: Reset Content
/ "206" ; [Part5], Section 3.1: Partial Content
/ "300" ; Section 8.3.1: Multiple Choices
/ "301" ; Section 8.3.2: Moved Permanently
/ "302" ; Section 8.3.3: Found
/ "303" ; Section 8.3.4: See Other
/ "304" ; [Part4], Section 3.1: Not Modified
/ "305" ; Section 8.3.6: Use Proxy
/ "307" ; Section 8.3.8: Temporary Redirect
/ "400" ; Section 8.4.1: Bad Request
/ "401" ; [Part7], Section 2.1: Unauthorized
/ "402" ; Section 8.4.3: Payment Required
/ "403" ; Section 8.4.4: Forbidden
/ "404" ; Section 8.4.5: Not Found
/ "405" ; Section 8.4.6: Method Not Allowed
/ "406" ; Section 8.4.7: Not Acceptable
/ "407" ; [Part7], Section 2.2: Proxy Authentication Required
/ "408" ; Section 8.4.9: Request Time-out
/ "409" ; Section 8.4.10: Conflict
/ "410" ; Section 8.4.11: Gone
/ "411" ; Section 8.4.12: Length Required
/ "412" ; [Part4], Section 3.2: Precondition Failed
/ "413" ; Section 8.4.14: Request Entity Too Large
/ "414" ; Section 8.4.15: URI Too Long
/ "415" ; Section 8.4.16: Unsupported Media Type
/ "416" ; [Part5], Section 3.2: Requested range not satisfiable
/ "417" ; Section 8.4.18: Expectation Failed
/ "500" ; Section 8.5.1: Internal Server Error
/ "501" ; Section 8.5.2: Not Implemented
/ "502" ; Section 8.5.3: Bad Gateway
/ "503" ; Section 8.5.4: Service Unavailable
/ "504" ; Section 8.5.5: Gateway Time-out
/ "505" ; Section 8.5.6: HTTP Version not supported
/ extension-code
extension-code = 3DIGIT
Reason-Phrase = *( WSP / VCHAR / obs-text )
HTTP status codes are extensible. HTTP applications are not required
to understand the meaning of all registered status codes, though such
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understanding is obviously desirable. However, applications MUST
understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the
x00 status code of that class, with the exception that an
unrecognized response MUST NOT be cached. For example, if an
unrecognized status code of 431 is received by the client, it can
safely assume that there was something wrong with its request and
treat the response as if it had received a 400 status code. In such
cases, user agents SHOULD present to the user the representation
enclosed with the response, since that representation is likely to
include human-readable information which will explain the unusual
status.
4.1. Status Code Registry
The HTTP Status Code Registry defines the name space for the Status-
Code token in the Status-Line of an HTTP response.
Values to be added to this name space are subject to IETF review
([RFC5226], Section 4.1).
The registry itself is maintained at
<http://www.iana.org/assignments/http-status-codes>.
5. Response Header Fields
The response-header fields allow the server to pass additional
information about the response which cannot be placed in the Status-
Line. These header fields give information about the server and
about further access to the target resource (Section 4.3 of [Part1]).
response-header = Accept-Ranges ; [Part5], Section 5.1
/ Age ; [Part6], Section 3.1
/ Allow ; Section 9.1
/ ETag ; [Part4], Section 6.1
/ Location ; Section 9.4
/ Proxy-Authenticate ; [Part7], Section 3.2
/ Retry-After ; Section 9.7
/ Server ; Section 9.8
/ Vary ; [Part6], Section 3.5
/ WWW-Authenticate ; [Part7], Section 3.4
Response-header field names can be extended reliably only in
combination with a change in the protocol version. However, new or
experimental header fields MAY be given the semantics of response-
header fields if all parties in the communication recognize them to
be response-header fields.
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6. Representation
Request and Response messages MAY transfer a representation if not
otherwise restricted by the request method or response status code.
A representation consists of metadata (representation header fields)
and data (representation body). When a complete or partial
representation is enclosed in an HTTP message, it is referred to as
the payload of the message. HTTP representations are defined in
[Part3].
A representation body is only present in a message when a message-
body is present, as described in Section 3.3 of [Part1]. The
representation body is obtained from the message-body by decoding any
Transfer-Encoding that might have been applied to ensure safe and
proper transfer of the message.
6.1. Identifying the Resource Associated with a Representation
It is sometimes necessary to determine an identifier for the resource
associated with a representation.
An HTTP request representation, when present, is always associated
with an anonymous (i.e., unidentified) resource.
In the common case, an HTTP response is a representation of the
target resource (see Section 4.3 of [Part1]). However, this is not
always the case. To determine the URI of the resource a response is
associated with, the following rules are used (with the first
applicable one being selected):
1. If the response status code is 200 or 203 and the request method
was GET, the response payload is a representation of the target
resource.
2. If the response status code is 204, 206, or 304 and the request
method was GET or HEAD, the response payload is a partial
representation of the target (see Section 2.8 of [Part6]).
3. If the response has a Content-Location header, and that URI is
the same as the effective request URI, the response payload is a
representation of the target resource.
4. If the response has a Content-Location header, and that URI is
not the same as the effective request URI, then the response
asserts that its payload is a representation of the resource
identified by the Content-Location URI. However, such an
assertion cannot be trusted unless it can be verified by other
means (not defined by HTTP).
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5. Otherwise, the response is a representation of an anonymous
(i.e., unidentified) resource.
[[TODO-req-uri: The comparison function is going to have to be
defined somewhere, because we already need to compare URIs for things
like cache invalidation.]]
7. Method Definitions
The set of common methods for HTTP/1.1 is defined below. Although
this set can be expanded, additional methods cannot be assumed to
share the same semantics for separately extended clients and servers.
7.1. Safe and Idempotent Methods
7.1.1. Safe Methods
Implementors need to be aware that the software represents the user
in their interactions over the Internet, and need to allow the user
to be aware of any actions they take which might have an unexpected
significance to themselves or others.
In particular, the convention has been established that the GET,
HEAD, OPTIONS, and TRACE methods SHOULD NOT have the significance of
taking an action other than retrieval. These methods ought to be
considered "safe". This allows user agents to represent other
methods, such as POST, PUT and DELETE, in a special way, so that the
user is made aware of the fact that a possibly unsafe action is being
requested.
Naturally, it is not possible to ensure that the server does not
generate side-effects as a result of performing a GET request; in
fact, some dynamic resources consider that a feature. The important
distinction here is that the user did not request the side-effects,
so therefore cannot be held accountable for them.
7.1.2. Idempotent Methods
Methods can also have the property of "idempotence" in that, aside
from error or expiration issues, the intended effect of multiple
identical requests is the same as for a single request. The methods
PUT, DELETE, and all safe methods are idempotent. It is important to
note that idempotence refers only to changes requested by the client:
a server is free to change its state due to multiple requests for the
purpose of tracking those requests, versioning of results, etc.
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7.2. OPTIONS
The OPTIONS method represents a request for information about the
communication options available on the request/response chain
identified by the effective request URI. This method allows the
client to determine the options and/or requirements associated with a
resource, or the capabilities of a server, without implying a
resource action or initiating a resource retrieval.
Responses to this method are not cacheable.
If the OPTIONS request includes a message-body (as indicated by the
presence of Content-Length or Transfer-Encoding), then the media type
MUST be indicated by a Content-Type field. Although this
specification does not define any use for such a body, future
extensions to HTTP might use the OPTIONS body to make more detailed
queries on the server.
If the request-target is an asterisk ("*"), the OPTIONS request is
intended to apply to the server in general rather than to a specific
resource. Since a server's communication options typically depend on
the resource, the "*" request is only useful as a "ping" or "no-op"
type of method; it does nothing beyond allowing the client to test
the capabilities of the server. For example, this can be used to
test a proxy for HTTP/1.1 compliance (or lack thereof).
If the request-target is not an asterisk, the OPTIONS request applies
only to the options that are available when communicating with that
resource.
A 200 response SHOULD include any header fields that indicate
optional features implemented by the server and applicable to that
resource (e.g., Allow), possibly including extensions not defined by
this specification. The response body, if any, SHOULD also include
information about the communication options. The format for such a
body is not defined by this specification, but might be defined by
future extensions to HTTP. Content negotiation MAY be used to select
the appropriate response format. If no response body is included,
the response MUST include a Content-Length field with a field-value
of "0".
The Max-Forwards request-header field MAY be used to target a
specific proxy in the request chain (see Section 9.5). If no Max-
Forwards field is present in the request, then the forwarded request
MUST NOT include a Max-Forwards field.
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7.3. GET
The GET method means retrieve whatever information (in the form of a
representation) currently corresponds to the target resource.
If the target resource is a data-producing process, it is the
produced data which shall be returned as the representation in the
response and not the source text of the process, unless that text
happens to be the output of the process.
The semantics of the GET method change to a "conditional GET" if the
request message includes an If-Modified-Since, If-Unmodified-Since,
If-Match, If-None-Match, or If-Range header field. A conditional GET
method requests that the representation be transferred only under the
circumstances described by the conditional header field(s). The
conditional GET method is intended to reduce unnecessary network
usage by allowing cached representations to be refreshed without
requiring multiple requests or transferring data already held by the
client.
The semantics of the GET method change to a "partial GET" if the
request message includes a Range header field. A partial GET
requests that only part of the representation be transferred, as
described in Section 5.4 of [Part5]. The partial GET method is
intended to reduce unnecessary network usage by allowing partially-
retrieved representations to be completed without transferring data
already held by the client.
The response to a GET request is cacheable and MAY be used to satisfy
subsequent GET and HEAD requests (see [Part6]).
See Section 11.2 for security considerations when used for forms.
7.4. HEAD
The HEAD method is identical to GET except that the server MUST NOT
return a message-body in the response. The metadata contained in the
HTTP headers in response to a HEAD request SHOULD be identical to the
information sent in response to a GET request. This method can be
used for obtaining metadata about the representation implied by the
request without transferring the representation body. This method is
often used for testing hypertext links for validity, accessibility,
and recent modification.
The response to a HEAD request is cacheable and MAY be used to
satisfy a subsequent HEAD request; see [Part6]. It also MAY be used
to update a previously cached representation from that resource; if
the new field values indicate that the cached representation differs
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from the current representation (as would be indicated by a change in
Content-Length, Content-MD5, ETag or Last-Modified), then the cache
MUST treat the cache entry as stale.
7.5. POST
The POST method is used to request that the origin server accept the
representation enclosed in the request as data to be processed by the
target resource. POST is designed to allow a uniform method to cover
the following functions:
o Annotation of existing resources;
o Posting a message to a bulletin board, newsgroup, mailing list, or
similar group of articles;
o Providing a block of data, such as the result of submitting a
form, to a data-handling process;
o Extending a database through an append operation.
The actual function performed by the POST method is determined by the
server and is usually dependent on the effective request URI.
The action performed by the POST method might not result in a
resource that can be identified by a URI. In this case, either 200
(OK) or 204 (No Content) is the appropriate response status code,
depending on whether or not the response includes a representation
that describes the result.
If a resource has been created on the origin server, the response
SHOULD be 201 (Created) and contain a representation which describes
the status of the request and refers to the new resource, and a
Location header (see Section 9.4).
Responses to POST requests are only cacheable when they include
explicit freshness information (see Section 2.3.1 of [Part6]). A
cached POST response with a Content-Location header (see Section 6.7
of [Part3]) whose value is the effective Request URI MAY be used to
satisfy subsequent GET and HEAD requests.
Note that POST caching is not widely implemented. However, the 303
(See Other) response can be used to direct the user agent to retrieve
a cacheable resource.
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7.6. PUT
The PUT method requests that the enclosed representation be stored at
the effective request URI. If the effective request URI refers to an
already existing resource, the enclosed representation SHOULD be
considered a modified version of the one residing on the origin
server. Otherwise, if the effective request URI does not point to an
existing resource, and that URI is capable of being defined as a new
resource by the requesting user agent, the origin server can create
the resource with that URI.
If a new resource is created at the effective request URI, the origin
server MUST inform the user agent via the 201 (Created) response. If
an existing resource is modified, either the 200 (OK) or 204 (No
Content) response codes SHOULD be sent to indicate successful
completion of the request.
If the target resource could not be created or modified, an
appropriate error response SHOULD be given that reflects the nature
of the problem. The recipient of the representation MUST NOT ignore
any Content-* headers (headers starting with the prefix "Content-")
that it does not understand or implement and MUST return a 501 (Not
Implemented) response in such cases.
If the request passes through a cache that has one or more stored
responses for the effective request URI, those stored responses
SHOULD be marked as stale if the response to the PUT request has a
success status code. Responses to the PUT method are not cacheable.
The fundamental difference between the POST and PUT requests is
reflected in the different meaning of the effective request URI. The
URI in a POST request identifies the resource that will handle the
enclosed representation. That resource might be a data-accepting
process, a gateway to some other protocol, or a document that accepts
annotations. In contrast, the URI in a PUT request identifies the
resource for which enclosed representation is a new or replacement
value; the user agent knows what URI is intended and the server MUST
NOT attempt to apply the request to some other resource. If the
server desires that the request be applied to a different URI, it
MUST send a 301 (Moved Permanently) response; the user agent MAY then
make its own decision regarding whether or not to redirect the
request.
A single resource MAY be identified by many different URIs. For
example, an article might have a URI for identifying "the current
version" which is separate from the URI identifying each particular
version. In this case, a PUT request on a general URI might result
in several other URIs being defined by the origin server.
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HTTP/1.1 does not define how a PUT method affects the state of an
origin server.
Header fields in a PUT request that are recognized as representation
metadata SHOULD be applied to the resource created or modified by the
PUT. Unrecognized header fields SHOULD be ignored.
7.7. DELETE
The DELETE method requests that the origin server delete the target
resource. This method MAY be overridden by human intervention (or
other means) on the origin server. The client cannot be guaranteed
that the operation has been carried out, even if the status code
returned from the origin server indicates that the action has been
completed successfully. However, the server SHOULD NOT indicate
success unless, at the time the response is given, it intends to
delete the resource or move it to an inaccessible location.
A successful response SHOULD be 200 (OK) if the response includes an
representation describing the status, 202 (Accepted) if the action
has not yet been enacted, or 204 (No Content) if the action has been
enacted but the response does not include a representation.
If the request passes through a cache and the effective request URI
identifies one or more currently cached representations, those
entries SHOULD be treated as stale. Responses to the DELETE method
are not cacheable.
7.8. TRACE
The TRACE method is used to invoke a remote, application-layer loop-
back of the request message. The final recipient of the request
SHOULD reflect the message received back to the client as the
message-body of a 200 (OK) response. The final recipient is either
the origin server or the first proxy or gateway to receive a Max-
Forwards value of zero (0) in the request (see Section 9.5). A TRACE
request MUST NOT include a message-body.
TRACE allows the client to see what is being received at the other
end of the request chain and use that data for testing or diagnostic
information. The value of the Via header field (Section 9.9 of
[Part1]) is of particular interest, since it acts as a trace of the
request chain. Use of the Max-Forwards header field allows the
client to limit the length of the request chain, which is useful for
testing a chain of proxies forwarding messages in an infinite loop.
If the request is valid, the response SHOULD have a Content-Type of
"message/http" (see Section 10.3.1 of [Part1]) and contain a message-
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body that encloses a copy of the entire request message. Responses
to the TRACE method are not cacheable.
7.9. CONNECT
This specification reserves the method name CONNECT for use with a
proxy that can dynamically switch to being a tunnel (e.g., SSL
tunneling [RFC2817]).
8. Status Code Definitions
Each Status-Code is described below, including any metadata required
in the response.
8.1. Informational 1xx
This class of status code indicates a provisional response,
consisting only of the Status-Line and optional headers, and is
terminated by an empty line. There are no required headers for this
class of status code. Since HTTP/1.0 did not define any 1xx status
codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client
except under experimental conditions.
A client MUST be prepared to accept one or more 1xx status responses
prior to a regular response, even if the client does not expect a 100
(Continue) status message. Unexpected 1xx status responses MAY be
ignored by a user agent.
Proxies MUST forward 1xx responses, unless the connection between the
proxy and its client has been closed, or unless the proxy itself
requested the generation of the 1xx response. (For example, if a
proxy adds a "Expect: 100-continue" field when it forwards a request,
then it need not forward the corresponding 100 (Continue)
response(s).)
8.1.1. 100 Continue
The client SHOULD continue with its request. This interim response
is used to inform the client that the initial part of the request has
been received and has not yet been rejected by the server. The
client SHOULD continue by sending the remainder of the request or, if
the request has already been completed, ignore this response. The
server MUST send a final response after the request has been
completed. See Section 7.2.3 of [Part1] for detailed discussion of
the use and handling of this status code.
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8.1.2. 101 Switching Protocols
The server understands and is willing to comply with the client's
request, via the Upgrade message header field (Section 9.8 of
[Part1]), for a change in the application protocol being used on this
connection. The server will switch protocols to those defined by the
response's Upgrade header field immediately after the empty line
which terminates the 101 response.
The protocol SHOULD be switched only when it is advantageous to do
so. For example, switching to a newer version of HTTP is
advantageous over older versions, and switching to a real-time,
synchronous protocol might be advantageous when delivering resources
that use such features.
8.2. Successful 2xx
This class of status code indicates that the client's request was
successfully received, understood, and accepted.
8.2.1. 200 OK
The request has succeeded. The payload returned with the response is
dependent on the method used in the request, for example:
GET a representation of the target resource is sent in the response;
HEAD the same representation as GET, except without the message-
body;
POST a representation describing or containing the result of the
action;
TRACE a representation containing the request message as received by
the end server.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 200 responses.
8.2.2. 201 Created
The request has been fulfilled and has resulted in a new resource
being created. The newly created resource can be referenced by the
URI(s) returned in the payload of the response, with the most
specific URI for the resource given by a Location header field. The
response SHOULD include a payload containing a list of resource
characteristics and location(s) from which the user or user agent can
choose the one most appropriate. The payload format is specified by
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the media type given in the Content-Type header field. The origin
server MUST create the resource before returning the 201 status code.
If the action cannot be carried out immediately, the server SHOULD
respond with 202 (Accepted) response instead.
A 201 response MAY contain an ETag response header field indicating
the current value of the entity-tag for the representation of the
resource just created (see Section 6.1 of [Part4]).
8.2.3. 202 Accepted
The request has been accepted for processing, but the processing has
not been completed. The request might or might not eventually be
acted upon, as it might be disallowed when processing actually takes
place. There is no facility for re-sending a status code from an
asynchronous operation such as this.
The 202 response is intentionally non-committal. Its purpose is to
allow a server to accept a request for some other process (perhaps a
batch-oriented process that is only run once per day) without
requiring that the user agent's connection to the server persist
until the process is completed. The representation returned with
this response SHOULD include an indication of the request's current
status and either a pointer to a status monitor or some estimate of
when the user can expect the request to be fulfilled.
8.2.4. 203 Non-Authoritative Information
The returned metadata in the header fields is not the definitive set
as available from the origin server, but is gathered from a local or
a third-party copy. The set presented MAY be a subset or superset of
the original version. For example, including local annotation
information about the resource might result in a superset of the
metadata known by the origin server. Use of this response code is
not required and is only appropriate when the response would
otherwise be 200 (OK).
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 203 responses.
8.2.5. 204 No Content
The server has successfully fulfilled the request, but there is no
additional content to return in the response payload body. The
resource metadata and representation metadata in the response
message's header fields refer to the target resource and its current
representation, respectively, after the requested action. For
example, if a 204 status code is received in response to a PUT and
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the response contains an ETag header field, then the value of that
field is the current entity-tag for the representation that was
successfully PUT.
If the client is a user agent, it SHOULD NOT change its document view
from that which caused the request to be sent. This response is
primarily intended to allow input for actions to take place without
causing a change to the user agent's active document view, although
any new or updated metadata SHOULD be applied to the document
currently in the user agent's active view.
The 204 response MUST NOT include a message-body, and thus is always
terminated by the first empty line after the header fields.
8.2.6. 205 Reset Content
The server has fulfilled the request and the user agent SHOULD reset
the document view which caused the request to be sent. This response
is primarily intended to allow input for actions to take place via
user input, followed by a clearing of the form in which the input is
given so that the user can easily initiate another input action. The
response MUST NOT include a message-body.
8.2.7. 206 Partial Content
The server has fulfilled the partial GET request for the resource and
the enclosed payload is a partial representation as defined in
Section 3.1 of [Part5].
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 206 responses.
8.3. Redirection 3xx
This class of status code indicates that further action needs to be
taken by the user agent in order to fulfill the request. The action
required MAY be carried out by the user agent without interaction
with the user if and only if the method used in the second request is
known to be "safe", as defined in Section 7.1.1. A client SHOULD
detect infinite redirection loops, since such loops generate network
traffic for each redirection.
Note: An earlier version of this specification recommended a
maximum of five redirections ([RFC2068], Section 10.3). Content
developers need to be aware that some clients might implement such
a fixed limitation.
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8.3.1. 300 Multiple Choices
The target resource more than one representation, each with its own
specific location, and agent-driven negotiation information (Section
5 of [Part3]) is being provided so that the user (or user agent) can
select a preferred representation by redirecting its request to that
location.
Unless it was a HEAD request, the response SHOULD include a
representation containing a list of representation metadata and
location(s) from which the user or user agent can choose the one most
appropriate. The data format is specified by the media type given in
the Content-Type header field. Depending upon the format and the
capabilities of the user agent, selection of the most appropriate
choice MAY be performed automatically. However, this specification
does not define any standard for such automatic selection.
If the server has a preferred choice of representation, it SHOULD
include the specific URI for that representation in the Location
field; user agents MAY use the Location field value for automatic
redirection.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 300 responses.
8.3.2. 301 Moved Permanently
The target resource has been assigned a new permanent URI and any
future references to this resource SHOULD use one of the returned
URIs. Clients with link editing capabilities ought to automatically
re-link references to the effective request URI to one or more of the
new references returned by the server, where possible.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 301 responses.
The new permanent URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the representation of
the response SHOULD contain a short hypertext note with a hyperlink
to the new URI(s).
If the 301 status code is received in response to a request method
that is known to be "safe", as defined in Section 7.1.1, then the
request MAY be automatically redirected by the user agent without
confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued.
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Note: When automatically redirecting a POST request after
receiving a 301 status code, some existing HTTP/1.0 user agents
will erroneously change it into a GET request.
8.3.3. 302 Found
The target resource resides temporarily under a different URI. Since
the redirection might be altered on occasion, the client SHOULD
continue to use the effective request URI for future requests.
The temporary URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the representation of
the response SHOULD contain a short hypertext note with a hyperlink
to the new URI(s).
If the 302 status code is received in response to a request method
that is known to be "safe", as defined in Section 7.1.1, then the
request MAY be automatically redirected by the user agent without
confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued.
Note: HTTP/1.0 ([RFC1945], Section 9.3) and the first version of
HTTP/1.1 ([RFC2068], Section 10.3.3) specify that the client is
not allowed to change the method on the redirected request.
However, most existing user agent implementations treat 302 as if
it were a 303 response, performing a GET on the Location field-
value regardless of the original request method. Therefore, a
previous version of this specification ([RFC2616], Section 10.3.3)
has added the status codes 303 and 307 for servers that wish to
make unambiguously clear which kind of reaction is expected of the
client.
8.3.4. 303 See Other
The server directs the user agent to a different resource, indicated
by a URI in the Location header field, that provides an indirect
response to the original request. The user agent MAY perform a GET
request on the URI in the Location field in order to obtain a
representation corresponding to the response, be redirected again, or
end with an error status. The Location URI is not a substitute
reference for the effective request URI.
The 303 status code is generally applicable to any HTTP method. It
is primarily used to allow the output of a POST action to redirect
the user agent to a selected resource, since doing so provides the
information corresponding to the POST response in a form that can be
separately identified, bookmarked, and cached independent of the
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original request.
A 303 response to a GET request indicates that the requested resource
does not have a representation of its own that can be transferred by
the server over HTTP. The Location URI indicates a resource that is
descriptive of the target resource, such that the follow-on
representation might be useful to recipients without implying that it
adequately represents the target resource. Note that answers to the
questions of what can be represented, what representations are
adequate, and what might be a useful description are outside the
scope of HTTP and thus entirely determined by the URI owner(s).
Except for responses to a HEAD request, the representation of a 303
response SHOULD contain a short hypertext note with a hyperlink to
the Location URI.
8.3.5. 304 Not Modified
The response to the request has not been modified since the
conditions indicated by the client's conditional GET request, as
defined in Section 3.1 of [Part4].
8.3.6. 305 Use Proxy
The 305 status code was defined in a previous version of this
specification (see Appendix A), and is now deprecated.
8.3.7. 306 (Unused)
The 306 status code was used in a previous version of the
specification, is no longer used, and the code is reserved.
8.3.8. 307 Temporary Redirect
The target resource resides temporarily under a different URI. Since
the redirection can change over time, the client SHOULD continue to
use the effective request URI for future requests.
The temporary URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the representation of
the response SHOULD contain a short hypertext note with a hyperlink
to the new URI(s) , since many pre-HTTP/1.1 user agents do not
understand the 307 status code. Therefore, the note SHOULD contain
the information necessary for a user to repeat the original request
on the new URI.
If the 307 status code is received in response to a request method
that is known to be "safe", as defined in Section 7.1.1, then the
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request MAY be automatically redirected by the user agent without
confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued.
8.4. Client Error 4xx
The 4xx class of status code is intended for cases in which the
client seems to have erred. Except when responding to a HEAD
request, the server SHOULD include a representation containing an
explanation of the error situation, and whether it is a temporary or
permanent condition. These status codes are applicable to any
request method. User agents SHOULD display any included
representation to the user.
If the client is sending data, a server implementation using TCP
SHOULD be careful to ensure that the client acknowledges receipt of
the packet(s) containing the response, before the server closes the
input connection. If the client continues sending data to the server
after the close, the server's TCP stack will send a reset packet to
the client, which might erase the client's unacknowledged input
buffers before they can be read and interpreted by the HTTP
application.
8.4.1. 400 Bad Request
The request could not be understood by the server due to malformed
syntax. The client SHOULD NOT repeat the request without
modifications.
8.4.2. 401 Unauthorized
The request requires user authentication (see Section 2.1 of
[Part7]).
8.4.3. 402 Payment Required
This code is reserved for future use.
8.4.4. 403 Forbidden
The server understood the request, but is refusing to fulfill it.
Authorization will not help and the request SHOULD NOT be repeated.
If the request method was not HEAD and the server wishes to make
public why the request has not been fulfilled, it SHOULD describe the
reason for the refusal in the representation. If the server does not
wish to make this information available to the client, the status
code 404 (Not Found) can be used instead.
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8.4.5. 404 Not Found
The server has not found anything matching the effective request URI.
No indication is given of whether the condition is temporary or
permanent. The 410 (Gone) status code SHOULD be used if the server
knows, through some internally configurable mechanism, that an old
resource is permanently unavailable and has no forwarding address.
This status code is commonly used when the server does not wish to
reveal exactly why the request has been refused, or when no other
response is applicable.
8.4.6. 405 Method Not Allowed
The method specified in the Request-Line is not allowed for the
target resource. The response MUST include an Allow header
containing a list of valid methods for the requested resource.
8.4.7. 406 Not Acceptable
The resource identified by the request is only capable of generating
response representations which have content characteristics not
acceptable according to the accept headers sent in the request.
Unless it was a HEAD request, the response SHOULD include a
representation containing a list of available representation
characteristics and location(s) from which the user or user agent can
choose the one most appropriate. The data format is specified by the
media type given in the Content-Type header field. Depending upon
the format and the capabilities of the user agent, selection of the
most appropriate choice MAY be performed automatically. However,
this specification does not define any standard for such automatic
selection.
Note: HTTP/1.1 servers are allowed to return responses which are
not acceptable according to the accept headers sent in the
request. In some cases, this might even be preferable to sending
a 406 response. User agents are encouraged to inspect the headers
of an incoming response to determine if it is acceptable.
If the response could be unacceptable, a user agent SHOULD
temporarily stop receipt of more data and query the user for a
decision on further actions.
8.4.8. 407 Proxy Authentication Required
This code is similar to 401 (Unauthorized), but indicates that the
client must first authenticate itself with the proxy (see Section 2.2
of [Part7]).
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8.4.9. 408 Request Timeout
The client did not produce a request within the time that the server
was prepared to wait. The client MAY repeat the request without
modifications at any later time.
8.4.10. 409 Conflict
The request could not be completed due to a conflict with the current
state of the resource. This code is only allowed in situations where
it is expected that the user might be able to resolve the conflict
and resubmit the request. The response body SHOULD include enough
information for the user to recognize the source of the conflict.
Ideally, the response representation would include enough information
for the user or user agent to fix the problem; however, that might
not be possible and is not required.
Conflicts are most likely to occur in response to a PUT request. For
example, if versioning were being used and the representation being
PUT included changes to a resource which conflict with those made by
an earlier (third-party) request, the server might use the 409
response to indicate that it can't complete the request. In this
case, the response representation would likely contain a list of the
differences between the two versions in a format defined by the
response Content-Type.
8.4.11. 410 Gone
The target resource is no longer available at the server and no
forwarding address is known. This condition is expected to be
considered permanent. Clients with link editing capabilities SHOULD
delete references to the effective request URI after user approval.
If the server does not know, or has no facility to determine, whether
or not the condition is permanent, the status code 404 (Not Found)
SHOULD be used instead.
The 410 response is primarily intended to assist the task of web
maintenance by notifying the recipient that the resource is
intentionally unavailable and that the server owners desire that
remote links to that resource be removed. Such an event is common
for limited-time, promotional services and for resources belonging to
individuals no longer working at the server's site. It is not
necessary to mark all permanently unavailable resources as "gone" or
to keep the mark for any length of time -- that is left to the
discretion of the server owner.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 410 responses.
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8.4.12. 411 Length Required
The server refuses to accept the request without a defined Content-
Length. The client MAY repeat the request if it adds a valid
Content-Length header field containing the length of the message-body
in the request message.
8.4.13. 412 Precondition Failed
The precondition given in one or more of the request-header fields
evaluated to false when it was tested on the server, as defined in
Section 3.2 of [Part4].
8.4.14. 413 Request Entity Too Large
The server is refusing to process a request because the request
representation is larger than the server is willing or able to
process. The server MAY close the connection to prevent the client
from continuing the request.
If the condition is temporary, the server SHOULD include a Retry-
After header field to indicate that it is temporary and after what
time the client MAY try again.
8.4.15. 414 URI Too Long
The server is refusing to service the request because the effective
request URI is longer than the server is willing to interpret. This
rare condition is only likely to occur when a client has improperly
converted a POST request to a GET request with long query
information, when the client has descended into a URI "black hole" of
redirection (e.g., a redirected URI prefix that points to a suffix of
itself), or when the server is under attack by a client attempting to
exploit security holes present in some servers using fixed-length
buffers for reading or manipulating the effective request URI.
8.4.16. 415 Unsupported Media Type
The server is refusing to service the request because the
representation of the request is in a format not supported by the
target resource for the requested method.
8.4.17. 416 Requested Range Not Satisfiable
The request included a Range request-header field (Section 5.4 of
[Part5]) and none of the range-specifier values in this field overlap
the current extent of the selected resource. See Section 3.2 of
[Part5].
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8.4.18. 417 Expectation Failed
The expectation given in an Expect request-header field (see
Section 9.2) could not be met by this server, or, if the server is a
proxy, the server has unambiguous evidence that the request could not
be met by the next-hop server.
8.5. Server Error 5xx
Response status codes beginning with the digit "5" indicate cases in
which the server is aware that it has erred or is incapable of
performing the request. Except when responding to a HEAD request,
the server SHOULD include a representation containing an explanation
of the error situation, and whether it is a temporary or permanent
condition. User agents SHOULD display any included representation to
the user. These response codes are applicable to any request method.
8.5.1. 500 Internal Server Error
The server encountered an unexpected condition which prevented it
from fulfilling the request.
8.5.2. 501 Not Implemented
The server does not support the functionality required to fulfill the
request. This is the appropriate response when the server does not
recognize the request method and is not capable of supporting it for
any resource.
8.5.3. 502 Bad Gateway
The server, while acting as a gateway or proxy, received an invalid
response from the upstream server it accessed in attempting to
fulfill the request.
8.5.4. 503 Service Unavailable
The server is currently unable to handle the request due to a
temporary overloading or maintenance of the server. The implication
is that this is a temporary condition which will be alleviated after
some delay. If known, the length of the delay MAY be indicated in a
Retry-After header. If no Retry-After is given, the client SHOULD
handle the response as it would for a 500 response.
Note: The existence of the 503 status code does not imply that a
server must use it when becoming overloaded. Some servers might
wish to simply refuse the connection.
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8.5.5. 504 Gateway Timeout
The server, while acting as a gateway or proxy, did not receive a
timely response from the upstream server specified by the URI (e.g.,
HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
to access in attempting to complete the request.
Note to implementors: some deployed proxies are known to return
400 or 500 when DNS lookups time out.
8.5.6. 505 HTTP Version Not Supported
The server does not support, or refuses to support, the protocol
version that was used in the request message. The server is
indicating that it is unable or unwilling to complete the request
using the same major version as the client, as described in Section
2.5 of [Part1], other than with this error message. The response
SHOULD contain a representation describing why that version is not
supported and what other protocols are supported by that server.
9. Header Field Definitions
This section defines the syntax and semantics of HTTP/1.1 header
fields related to request and response semantics.
9.1. Allow
The "Allow" response-header field lists the set of methods advertised
as supported by the target resource. The purpose of this field is
strictly to inform the recipient of valid methods associated with the
resource.
Allow = "Allow" ":" OWS Allow-v
Allow-v = #Method
Example of use:
Allow: GET, HEAD, PUT
The actual set of allowed methods is defined by the origin server at
the time of each request.
A proxy MUST NOT modify the Allow header field even if it does not
understand all the methods specified, since the user agent might have
other means of communicating with the origin server.
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9.2. Expect
The "Expect" request-header field is used to indicate that particular
server behaviors are required by the client.
Expect = "Expect" ":" OWS Expect-v
Expect-v = 1#expectation
expectation = "100-continue" / expectation-extension
expectation-extension = token [ "=" ( token / quoted-string )
*expect-params ]
expect-params = ";" token [ "=" ( token / quoted-string ) ]
A server that does not understand or is unable to comply with any of
the expectation values in the Expect field of a request MUST respond
with appropriate error status code. The server MUST respond with a
417 (Expectation Failed) status code if any of the expectations
cannot be met or, if there are other problems with the request, some
other 4xx status code.
This header field is defined with extensible syntax to allow for
future extensions. If a server receives a request containing an
Expect field that includes an expectation-extension that it does not
support, it MUST respond with a 417 (Expectation Failed) status code.
Comparison of expectation values is case-insensitive for unquoted
tokens (including the 100-continue token), and is case-sensitive for
quoted-string expectation-extensions.
The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST
return a 417 (Expectation Failed) status code if it receives a
request with an expectation that it cannot meet. However, the Expect
request-header itself is end-to-end; it MUST be forwarded if the
request is forwarded.
Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
Expect header.
See Section 7.2.3 of [Part1] for the use of the 100 (Continue) status
code.
9.3. From
The "From" request-header field, if given, SHOULD contain an Internet
e-mail address for the human user who controls the requesting user
agent. The address SHOULD be machine-usable, as defined by "mailbox"
in Section 3.4 of [RFC5322]:
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From = "From" ":" OWS From-v
From-v = mailbox
mailbox = <mailbox, defined in [RFC5322], Section 3.4>
An example is:
From: webmaster@example.org
This header field MAY be used for logging purposes and as a means for
identifying the source of invalid or unwanted requests. It SHOULD
NOT be used as an insecure form of access protection. The
interpretation of this field is that the request is being performed
on behalf of the person given, who accepts responsibility for the
method performed. In particular, robot agents SHOULD include this
header so that the person responsible for running the robot can be
contacted if problems occur on the receiving end.
The Internet e-mail address in this field MAY be separate from the
Internet host which issued the request. For example, when a request
is passed through a proxy the original issuer's address SHOULD be
used.
The client SHOULD NOT send the From header field without the user's
approval, as it might conflict with the user's privacy interests or
their site's security policy. It is strongly recommended that the
user be able to disable, enable, and modify the value of this field
at any time prior to a request.
9.4. Location
The "Location" response-header field is used to identify a newly
created resource, or to redirect the recipient to a different
location for completion of the request.
For 201 (Created) responses, the Location is the URI of the new
resource which was created by the request. For 3xx responses, the
location SHOULD indicate the server's preferred URI for automatic
redirection to the resource.
The field value consists of a single URI-reference. When it has the
form of a relative reference ([RFC3986], Section 4.2), the final
value is computed by resolving it against the effective request URI
([RFC3986], Section 5).
Location = "Location" ":" OWS Location-v
Location-v = URI-reference
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Examples are:
Location: http://www.example.org/pub/WWW/People.html#tim
Location: /index.html
There are circumstances in which a fragment identifier in a Location
URI would not be appropriate:
o With a 201 Created response, because in this usage the Location
header specifies the URI for the entire created resource.
o With 305 Use Proxy.
Note: This specification does not define precedence rules for the
case where the original URI, as navigated to by the user agent,
and the Location header field value both contain fragment
identifiers.
Note: The Content-Location header field (Section 6.7 of [Part3])
differs from Location in that the Content-Location identifies the
most specific resource corresponding to the enclosed
representation. It is therefore possible for a response to
contain header fields for both Location and Content-Location.
9.5. Max-Forwards
The "Max-Forwards" request-header field provides a mechanism with the
TRACE (Section 7.8) and OPTIONS (Section 7.2) methods to limit the
number of times that the request is forwarded by proxies or gateways.
This can be useful when the client is attempting to trace a request
which appears to be failing or looping in mid-chain.
Max-Forwards = "Max-Forwards" ":" OWS Max-Forwards-v
Max-Forwards-v = 1*DIGIT
The Max-Forwards value is a decimal integer indicating the remaining
number of times this request message can be forwarded.
Each proxy or gateway recipient of a TRACE or OPTIONS request
containing a Max-Forwards header field MUST check and update its
value prior to forwarding the request. If the received value is zero
(0), the recipient MUST NOT forward the request; instead, it MUST
respond as the final recipient. If the received Max-Forwards value
is greater than zero, then the forwarded message MUST contain an
updated Max-Forwards field with a value decremented by one (1).
The Max-Forwards header field MAY be ignored for all other methods
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defined by this specification and for any extension methods for which
it is not explicitly referred to as part of that method definition.
9.6. Referer
The "Referer" [sic] request-header field allows the client to specify
the URI of the resource from which the effective request URI was
obtained (the "referrer", although the header field is misspelled.).
The Referer header allows servers to generate lists of back-links to
resources for interest, logging, optimized caching, etc. It also
allows obsolete or mistyped links to be traced for maintenance. Some
servers use Referer as a means of controlling where they allow links
from (so-called "deep linking"), but legitimate requests do not
always contain a Referer header field.
If the effective request URI was obtained from a source that does not
have its own URI (e.g., input from the user keyboard), the Referer
field MUST either be sent with the value "about:blank", or not be
sent at all. Note that this requirement does not apply to sources
with non-HTTP URIs (e.g., FTP).
Referer = "Referer" ":" OWS Referer-v
Referer-v = absolute-URI / partial-URI
Example:
Referer: http://www.example.org/hypertext/Overview.html
If the field value is a relative URI, it SHOULD be interpreted
relative to the effective request URI. The URI MUST NOT include a
fragment. See Section 11.2 for security considerations.
9.7. Retry-After
The response-header "Retry-After" field can be used with a 503
(Service Unavailable) response to indicate how long the service is
expected to be unavailable to the requesting client. This field MAY
also be used with any 3xx (Redirection) response to indicate the
minimum time the user-agent is asked wait before issuing the
redirected request.
The value of this field can be either an HTTP-date or an integer
number of seconds (in decimal) after the time of the response.
Retry-After = "Retry-After" ":" OWS Retry-After-v
Retry-After-v = HTTP-date / delta-seconds
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Time spans are non-negative decimal integers, representing time in
seconds.
delta-seconds = 1*DIGIT
Two examples of its use are
Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
Retry-After: 120
In the latter example, the delay is 2 minutes.
9.8. Server
The "Server" response-header field contains information about the
software used by the origin server to handle the request.
The field can contain multiple product tokens (Section 6.3 of
[Part1]) and comments (Section 3.2 of [Part1]) identifying the server
and any significant subproducts. The product tokens are listed in
order of their significance for identifying the application.
Server = "Server" ":" OWS Server-v
Server-v = product
*( RWS ( product / comment ) )
Example:
Server: CERN/3.0 libwww/2.17
If the response is being forwarded through a proxy, the proxy
application MUST NOT modify the Server response-header. Instead, it
MUST include a Via field (as described in Section 9.9 of [Part1]).
Note: Revealing the specific software version of the server might
allow the server machine to become more vulnerable to attacks
against software that is known to contain security holes. Server
implementors are encouraged to make this field a configurable
option.
9.9. User-Agent
The "User-Agent" request-header field contains information about the
user agent originating the request. This is for statistical
purposes, the tracing of protocol violations, and automated
recognition of user agents for the sake of tailoring responses to
avoid particular user agent limitations.
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User agents SHOULD include this field with requests. The field can
contain multiple product tokens (Section 6.3 of [Part1]) and comments
(Section 3.2 of [Part1]) identifying the agent and any subproducts
which form a significant part of the user agent. By convention, the
product tokens are listed in order of their significance for
identifying the application.
User-Agent = "User-Agent" ":" OWS User-Agent-v
User-Agent-v = product
*( RWS ( product / comment ) )
Example:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3
10. IANA Considerations
10.1. Method Registry
The registration procedure for HTTP Methods is defined by Section 2.1
of this document.
The HTTP Method Registry shall be created at
<http://www.iana.org/assignments/http-methods> and be populated with
the registrations below:
+---------+------+-------------+
| Method | Safe | Reference |
+---------+------+-------------+
| CONNECT | no | Section 7.9 |
| DELETE | no | Section 7.7 |
| GET | yes | Section 7.3 |
| HEAD | yes | Section 7.4 |
| OPTIONS | yes | Section 7.2 |
| POST | no | Section 7.5 |
| PUT | no | Section 7.6 |
| TRACE | yes | Section 7.8 |
+---------+------+-------------+
10.2. Status Code Registry
The registration procedure for HTTP Status Codes -- previously
defined in Section 7.1 of [RFC2817] -- is now defined by Section 4.1
of this document.
The HTTP Status Code Registry located at
<http://www.iana.org/assignments/http-status-codes> shall be updated
with the registrations below:
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+-------+-------------------------------+----------------+
| Value | Description | Reference |
+-------+-------------------------------+----------------+
| 100 | Continue | Section 8.1.1 |
| 101 | Switching Protocols | Section 8.1.2 |
| 200 | OK | Section 8.2.1 |
| 201 | Created | Section 8.2.2 |
| 202 | Accepted | Section 8.2.3 |
| 203 | Non-Authoritative Information | Section 8.2.4 |
| 204 | No Content | Section 8.2.5 |
| 205 | Reset Content | Section 8.2.6 |
| 300 | Multiple Choices | Section 8.3.1 |
| 301 | Moved Permanently | Section 8.3.2 |
| 302 | Found | Section 8.3.3 |
| 303 | See Other | Section 8.3.4 |
| 305 | Use Proxy | Section 8.3.6 |
| 306 | (Unused) | Section 8.3.7 |
| 307 | Temporary Redirect | Section 8.3.8 |
| 400 | Bad Request | Section 8.4.1 |
| 402 | Payment Required | Section 8.4.3 |
| 403 | Forbidden | Section 8.4.4 |
| 404 | Not Found | Section 8.4.5 |
| 405 | Method Not Allowed | Section 8.4.6 |
| 406 | Not Acceptable | Section 8.4.7 |
| 407 | Proxy Authentication Required | Section 8.4.8 |
| 408 | Request Timeout | Section 8.4.9 |
| 409 | Conflict | Section 8.4.10 |
| 410 | Gone | Section 8.4.11 |
| 411 | Length Required | Section 8.4.12 |
| 413 | Request Entity Too Large | Section 8.4.14 |
| 414 | URI Too Long | Section 8.4.15 |
| 415 | Unsupported Media Type | Section 8.4.16 |
| 417 | Expectation Failed | Section 8.4.18 |
| 500 | Internal Server Error | Section 8.5.1 |
| 501 | Not Implemented | Section 8.5.2 |
| 502 | Bad Gateway | Section 8.5.3 |
| 503 | Service Unavailable | Section 8.5.4 |
| 504 | Gateway Timeout | Section 8.5.5 |
| 505 | HTTP Version Not Supported | Section 8.5.6 |
+-------+-------------------------------+----------------+
10.3. Header Field Registration
The Message Header Field Registry located at <http://www.iana.org/
assignments/message-headers/message-header-index.html> shall be
updated with the permanent registrations below (see [RFC3864]):
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+-------------------+----------+----------+-------------+
| Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-------------+
| Allow | http | standard | Section 9.1 |
| Expect | http | standard | Section 9.2 |
| From | http | standard | Section 9.3 |
| Location | http | standard | Section 9.4 |
| Max-Forwards | http | standard | Section 9.5 |
| Referer | http | standard | Section 9.6 |
| Retry-After | http | standard | Section 9.7 |
| Server | http | standard | Section 9.8 |
| User-Agent | http | standard | Section 9.9 |
+-------------------+----------+----------+-------------+
The change controller is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force".
11. Security Considerations
This section is meant to inform application developers, information
providers, and users of the security limitations in HTTP/1.1 as
described by this document. The discussion does not include
definitive solutions to the problems revealed, though it does make
some suggestions for reducing security risks.
11.1. Transfer of Sensitive Information
Like any generic data transfer protocol, HTTP cannot regulate the
content of the data that is transferred, nor is there any a priori
method of determining the sensitivity of any particular piece of
information within the context of any given request. Therefore,
applications SHOULD supply as much control over this information as
possible to the provider of that information. Four header fields are
worth special mention in this context: Server, Via, Referer and From.
Revealing the specific software version of the server might allow the
server machine to become more vulnerable to attacks against software
that is known to contain security holes. Implementors SHOULD make
the Server header field a configurable option.
Proxies which serve as a portal through a network firewall SHOULD
take special precautions regarding the transfer of header information
that identifies the hosts behind the firewall. In particular, they
SHOULD remove, or replace with sanitized versions, any Via fields
generated behind the firewall.
The Referer header allows reading patterns to be studied and reverse
links drawn. Although it can be very useful, its power can be abused
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if user details are not separated from the information contained in
the Referer. Even when the personal information has been removed,
the Referer header might indicate a private document's URI whose
publication would be inappropriate.
The information sent in the From field might conflict with the user's
privacy interests or their site's security policy, and hence it
SHOULD NOT be transmitted without the user being able to disable,
enable, and modify the contents of the field. The user MUST be able
to set the contents of this field within a user preference or
application defaults configuration.
We suggest, though do not require, that a convenient toggle interface
be provided for the user to enable or disable the sending of From and
Referer information.
The User-Agent (Section 9.9) or Server (Section 9.8) header fields
can sometimes be used to determine that a specific client or server
have a particular security hole which might be exploited.
Unfortunately, this same information is often used for other valuable
purposes for which HTTP currently has no better mechanism.
Some methods, like TRACE (Section 7.8), expose information that was
sent in request headers within the body of their response. Clients
SHOULD be careful with sensitive information, like Cookies,
Authorization credentials and other headers that might be used to
collect data from the client.
11.2. Encoding Sensitive Information in URIs
Because the source of a link might be private information or might
reveal an otherwise private information source, it is strongly
recommended that the user be able to select whether or not the
Referer field is sent. For example, a browser client could have a
toggle switch for browsing openly/anonymously, which would
respectively enable/disable the sending of Referer and From
information.
Clients SHOULD NOT include a Referer header field in a (non-secure)
HTTP request if the referring page was transferred with a secure
protocol.
Authors of services SHOULD NOT use GET-based forms for the submission
of sensitive data because that data will be placed in the request-
target. Many existing servers, proxies, and user agents log or
display the request-target in places where it might be visible to
third parties. Such services can use POST-based form submission
instead.
Fielding, et al. Expires February 5, 2011 [Page 41]
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11.3. Location Headers and Spoofing
If a single server supports multiple organizations that do not trust
one another, then it MUST check the values of Location and Content-
Location headers in responses that are generated under control of
said organizations to make sure that they do not attempt to
invalidate resources over which they have no authority.
12. Acknowledgments
13. References
13.1. Normative References
[Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections,
and Message Parsing", draft-ietf-httpbis-p1-messaging-11
(work in progress), August 2010.
[Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload
and Content Negotiation", draft-ietf-httpbis-p3-payload-11
(work in progress), August 2010.
[Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional
Requests", draft-ietf-httpbis-p4-conditional-11 (work in
progress), August 2010.
[Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and
Partial Responses", draft-ietf-httpbis-p5-range-11 (work
in progress), August 2010.
[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
Nottingham, M., Ed., and J. Reschke, Ed., "HTTP/1.1, part
6: Caching", draft-ietf-httpbis-p6-cache-11 (work in
progress), August 2010.
[Part7] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 7: Authentication",
draft-ietf-httpbis-p7-auth-11 (work in progress),
Fielding, et al. Expires February 5, 2011 [Page 42]
Internet-Draft HTTP/1.1, Part 2 August 2010
August 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", RFC 3986,
STD 66, January 2005.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
13.2. Informative References
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext
Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
RFC 2068, January 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within
HTTP/1.1", RFC 2817, May 2000.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
October 2008.
Appendix A. Changes from RFC 2616
This document takes over the Status Code Registry, previously defined
in Section 7.1 of [RFC2817]. (Section 4.1)
Clarify definition of POST. (Section 7.5)
Failed to consider that there are many other request methods that are
safe to automatically redirect, and further that the user agent is
Fielding, et al. Expires February 5, 2011 [Page 43]
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able to make that determination based on the request method
semantics. (Sections 8.3.2, 8.3.3 and 8.3.8)
Deprecate 305 Use Proxy status code, because user agents did not
implement it. It used to indicate that the target resource must be
accessed through the proxy given by the Location field. The Location
field gave the URI of the proxy. The recipient was expected to
repeat this single request via the proxy. (Section 8.3.6)
Reclassify Allow header as response header, removing the option to
specify it in a PUT request. Relax the server requirement on the
contents of the Allow header and remove requirement on clients to
always trust the header value. (Section 9.1)
Correct syntax of Location header to allow URI references (including
relative references and fragments), as referred symbol "absoluteURI"
wasn't what was expected, and add some clarifications as to when use
of fragments would not be appropriate. (Section 9.4)
Allow Referer value of "about:blank" as alternative to not specifying
it. (Section 9.6)
In the description of the Server header, the Via field was described
as a SHOULD. The requirement was and is stated correctly in the
description of the Via header in Section 9.9 of [Part1].
(Section 9.8)
Appendix B. Collected ABNF
Accept = <Accept, defined in [Part3], Section 6.1>
Accept-Charset = <Accept-Charset, defined in [Part3], Section 6.2>
Accept-Encoding = <Accept-Encoding, defined in [Part3], Section 6.3>
Accept-Language = <Accept-Language, defined in [Part3], Section 6.4>
Accept-Ranges = <Accept-Ranges, defined in [Part5], Section 5.1>
Age = <Age, defined in [Part6], Section 3.1>
Allow = "Allow:" OWS Allow-v
Allow-v = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
Authorization = <Authorization, defined in [Part7], Section 3.1>
ETag = <ETag, defined in [Part4], Section 6.1>
Expect = "Expect:" OWS Expect-v
Expect-v = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
From = "From:" OWS From-v
From-v = mailbox
HTTP-date = <HTTP-date, defined in [Part1], Section 6.1>
Host = <Host, defined in [Part1], Section 2.6>
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If-Match = <If-Match, defined in [Part4], Section 6.2>
If-Modified-Since =
<If-Modified-Since, defined in [Part4], Section 6.3>
If-None-Match = <If-None-Match, defined in [Part4], Section 6.4>
If-Range = <If-Range, defined in [Part5], Section 5.3>
If-Unmodified-Since =
<If-Unmodified-Since, defined in [Part4], Section 6.5>
Location = "Location:" OWS Location-v
Location-v = URI-reference
Max-Forwards = "Max-Forwards:" OWS Max-Forwards-v
Max-Forwards-v = 1*DIGIT
Method = %x4F.50.54.49.4F.4E.53 ; OPTIONS
/ %x47.45.54 ; GET
/ %x48.45.41.44 ; HEAD
/ %x50.4F.53.54 ; POST
/ %x50.55.54 ; PUT
/ %x44.45.4C.45.54.45 ; DELETE
/ %x54.52.41.43.45 ; TRACE
/ %x43.4F.4E.4E.45.43.54 ; CONNECT
/ extension-method
OWS = <OWS, defined in [Part1], Section 1.2.2>
Proxy-Authenticate =
<Proxy-Authenticate, defined in [Part7], Section 3.2>
Proxy-Authorization =
<Proxy-Authorization, defined in [Part7], Section 3.3>
RWS = <RWS, defined in [Part1], Section 1.2.2>
Range = <Range, defined in [Part5], Section 5.4>
Reason-Phrase = *( WSP / VCHAR / obs-text )
Referer = "Referer:" OWS Referer-v
Referer-v = absolute-URI / partial-URI
Retry-After = "Retry-After:" OWS Retry-After-v
Retry-After-v = HTTP-date / delta-seconds
Server = "Server:" OWS Server-v
Server-v = product *( RWS ( product / comment ) )
Status-Code = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
"205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
"307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
"407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
"415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
"505" / extension-code
TE = <TE, defined in [Part1], Section 9.5>
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URI-reference = <URI-reference, defined in [Part1], Section 2.6>
User-Agent = "User-Agent:" OWS User-Agent-v
User-Agent-v = product *( RWS ( product / comment ) )
Vary = <Vary, defined in [Part6], Section 3.5>
WWW-Authenticate =
<WWW-Authenticate, defined in [Part7], Section 3.4>
absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
comment = <comment, defined in [Part1], Section 3.2>
delta-seconds = 1*DIGIT
expect-params = ";" token [ "=" ( token / quoted-string ) ]
expectation = "100-continue" / expectation-extension
expectation-extension = token [ "=" ( token / quoted-string )
*expect-params ]
extension-code = 3DIGIT
extension-method = token
mailbox = <mailbox, defined in [RFC5322], Section 3.4>
obs-text = <obs-text, defined in [Part1], Section 1.2.2>
partial-URI = <partial-URI, defined in [Part1], Section 2.6>
product = <product, defined in [Part1], Section 6.3>
quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
request-header = Accept / Accept-Charset / Accept-Encoding /
Accept-Language / Authorization / Expect / From / Host / If-Match /
If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
Max-Forwards / Proxy-Authorization / Range / Referer / TE /
User-Agent
response-header = Accept-Ranges / Age / Allow / ETag / Location /
Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
token = <token, defined in [Part1], Section 1.2.2>
ABNF diagnostics:
; Reason-Phrase defined but not used
; Status-Code defined but not used
; request-header defined but not used
; response-header defined but not used
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Appendix C. Change Log (to be removed by RFC Editor before publication)
C.1. Since RFC2616
Extracted relevant partitions from [RFC2616].
C.2. Since draft-ietf-httpbis-p2-semantics-00
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/5>: "Via is a MUST"
(<http://purl.org/NET/http-errata#via-must>)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/6>: "Fragments
allowed in Location"
(<http://purl.org/NET/http-errata#location-fragments>)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/10>: "Safe Methods
vs Redirection" (<http://purl.org/NET/http-errata#saferedirect>)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/17>: "Revise
description of the POST method"
(<http://purl.org/NET/http-errata#post>)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative and
Informative references"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/42>: "RFC2606
Compliance"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/65>: "Informative
references"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/84>: "Redundant
cross-references"
Other changes:
o Move definitions of 304 and 412 condition codes to [Part4]
C.3. Since draft-ietf-httpbis-p2-semantics-01
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/21>: "PUT side
effects"
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o <http://tools.ietf.org/wg/httpbis/trac/ticket/91>: "Duplicate Host
header requirements"
Ongoing work on ABNF conversion
(<http://tools.ietf.org/wg/httpbis/trac/ticket/36>):
o Move "Product Tokens" section (back) into Part 1, as "token" is
used in the definition of the Upgrade header.
o Add explicit references to BNF syntax and rules imported from
other parts of the specification.
o Copy definition of delta-seconds from Part6 instead of referencing
it.
C.4. Since draft-ietf-httpbis-p2-semantics-02
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/24>: "Requiring
Allow in 405 responses"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/59>: "Status Code
Registry"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/61>: "Redirection
vs. Location"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/70>: "Cacheability
of 303 response"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/76>: "305 Use Proxy"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/105>:
"Classification for Allow header"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/112>: "PUT - 'store
under' vs 'store at'"
Ongoing work on IANA Message Header Registration
(<http://tools.ietf.org/wg/httpbis/trac/ticket/40>):
o Reference RFC 3984, and update header registrations for headers
defined in this document.
Ongoing work on ABNF conversion
(<http://tools.ietf.org/wg/httpbis/trac/ticket/36>):
Fielding, et al. Expires February 5, 2011 [Page 48]
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o Replace string literals when the string really is case-sensitive
(method).
C.5. Since draft-ietf-httpbis-p2-semantics-03
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/98>: "OPTIONS
request bodies"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/119>: "Description
of CONNECT should refer to RFC2817"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/125>: "Location
Content-Location reference request/response mixup"
Ongoing work on Method Registry
(<http://tools.ietf.org/wg/httpbis/trac/ticket/72>):
o Added initial proposal for registration process, plus initial
content (non-HTTP/1.1 methods to be added by a separate
specification).
C.6. Since draft-ietf-httpbis-p2-semantics-04
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/103>: "Content-*"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/132>: "RFC 2822 is
updated by RFC 5322"
Ongoing work on ABNF conversion
(<http://tools.ietf.org/wg/httpbis/trac/ticket/36>):
o Use "/" instead of "|" for alternatives.
o Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
whitespace ("OWS") and required whitespace ("RWS").
o Rewrite ABNFs to spell out whitespace rules, factor out header
value format definitions.
C.7. Since draft-ietf-httpbis-p2-semantics-05
Closed issues:
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o <http://tools.ietf.org/wg/httpbis/trac/ticket/94>: "Reason-Phrase
BNF"
Final work on ABNF conversion
(<http://tools.ietf.org/wg/httpbis/trac/ticket/36>):
o Add appendix containing collected and expanded ABNF, reorganize
ABNF introduction.
C.8. Since draft-ietf-httpbis-p2-semantics-06
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/144>: "Clarify when
Referer is sent"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/164>: "status codes
vs methods"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/170>: "Do not
require "updates" relation for specs that register status codes or
method names"
C.9. Since draft-ietf-httpbis-p2-semantics-07
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/27>: "Idempotency"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/33>: "TRACE security
considerations"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/110>: "Clarify rules
for determining what entities a response carries"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/140>: "update note
citing RFC 1945 and 2068"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/182>: "update note
about redirect limit"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/191>: "Location
header ABNF should use 'URI'"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/192>: "fragments in
Location vs status 303"
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o <http://tools.ietf.org/wg/httpbis/trac/ticket/198>: "move IANA
registrations for optional status codes"
Partly resolved issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/171>: "Are OPTIONS
and TRACE safe?"
C.10. Since draft-ietf-httpbis-p2-semantics-08
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/10>: "Safe Methods
vs Redirection" (we missed the introduction to the 3xx status
codes when fixing this previously)
C.11. Since draft-ietf-httpbis-p2-semantics-09
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/43>: "Fragment
combination / precedence during redirects"
Partly resolved issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/185>: "Location
header payload handling"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/196>: "Term for the
requested resource's URI"
C.12. Since draft-ietf-httpbis-p2-semantics-10
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/69>: "Clarify
'Requested Variant'"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/109>: "Clarify
entity / representation / variant terminology"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/139>: "Methods and
Caching"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/190>: "OPTIONS vs
Max-Forwards"
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o <http://tools.ietf.org/wg/httpbis/trac/ticket/199>: "Status codes
and caching"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/220>: "consider
removing the 'changes from 2068' sections"
Index
1
100 Continue (status code) 20
101 Switching Protocols (status code) 21
2
200 OK (status code) 21
201 Created (status code) 21
202 Accepted (status code) 22
203 Non-Authoritative Information (status code) 22
204 No Content (status code) 22
205 Reset Content (status code) 23
206 Partial Content (status code) 23
3
300 Multiple Choices (status code) 24
301 Moved Permanently (status code) 24
302 Found (status code) 25
303 See Other (status code) 25
304 Not Modified (status code) 26
305 Use Proxy (status code) 26
306 (Unused) (status code) 26
307 Temporary Redirect (status code) 26
4
400 Bad Request (status code) 27
401 Unauthorized (status code) 27
402 Payment Required (status code) 27
403 Forbidden (status code) 27
404 Not Found (status code) 28
405 Method Not Allowed (status code) 28
406 Not Acceptable (status code) 28
407 Proxy Authentication Required (status code) 28
408 Request Timeout (status code) 29
409 Conflict (status code) 29
410 Gone (status code) 29
411 Length Required (status code) 30
412 Precondition Failed (status code) 30
413 Request Entity Too Large (status code) 30
414 URI Too Long (status code) 30
415 Unsupported Media Type (status code) 30
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416 Requested Range Not Satisfiable (status code) 30
417 Expectation Failed (status code) 31
5
500 Internal Server Error (status code) 31
501 Not Implemented (status code) 31
502 Bad Gateway (status code) 31
503 Service Unavailable (status code) 31
504 Gateway Timeout (status code) 32
505 HTTP Version Not Supported (status code) 32
A
Allow header 32
C
CONNECT method 20
D
DELETE method 19
E
Expect header 33
F
From header 33
G
GET method 16
Grammar
Allow 32
Allow-v 32
delta-seconds 37
Expect 33
expect-params 33
Expect-v 33
expectation 33
expectation-extension 33
extension-code 11
extension-method 8
From 34
From-v 34
Location 34
Location-v 34
Max-Forwards 35
Max-Forwards-v 35
Method 8
Reason-Phrase 11
Referer 36
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Referer-v 36
request-header 9
response-header 12
Retry-After 36
Retry-After-v 36
Server 37
Server-v 37
Status-Code 11
User-Agent 38
User-Agent-v 38
H
HEAD method 16
Headers
Allow 32
Expect 33
From 33
Location 34
Max-Forwards 35
Referer 36
Retry-After 36
Server 37
User-Agent 37
I
Idempotent Methods 14
L
Location header 34
M
Max-Forwards header 35
Methods
CONNECT 20
DELETE 19
GET 16
HEAD 16
OPTIONS 15
POST 17
PUT 18
TRACE 19
O
OPTIONS method 15
P
POST method 17
PUT method 18
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R
Referer header 36
Retry-After header 36
S
Safe Methods 14
Server header 37
Status Codes
100 Continue 20
101 Switching Protocols 21
200 OK 21
201 Created 21
202 Accepted 22
203 Non-Authoritative Information 22
204 No Content 22
205 Reset Content 23
206 Partial Content 23
300 Multiple Choices 24
301 Moved Permanently 24
302 Found 25
303 See Other 25
304 Not Modified 26
305 Use Proxy 26
306 (Unused) 26
307 Temporary Redirect 26
400 Bad Request 27
401 Unauthorized 27
402 Payment Required 27
403 Forbidden 27
404 Not Found 28
405 Method Not Allowed 28
406 Not Acceptable 28
407 Proxy Authentication Required 28
408 Request Timeout 29
409 Conflict 29
410 Gone 29
411 Length Required 30
412 Precondition Failed 30
413 Request Entity Too Large 30
414 URI Too Long 30
415 Unsupported Media Type 30
416 Requested Range Not Satisfiable 30
417 Expectation Failed 31
500 Internal Server Error 31
501 Not Implemented 31
502 Bad Gateway 31
503 Service Unavailable 31
504 Gateway Timeout 32
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505 HTTP Version Not Supported 32
T
TRACE method 19
U
User-Agent header 37
Authors' Addresses
Roy T. Fielding (editor)
Day Software
23 Corporate Plaza DR, Suite 280
Newport Beach, CA 92660
USA
Phone: +1-949-706-5300
Fax: +1-949-706-5305
EMail: fielding@gbiv.com
URI: http://roy.gbiv.com/
Jim Gettys
Alcatel-Lucent Bell Labs
21 Oak Knoll Road
Carlisle, MA 01741
USA
EMail: jg@freedesktop.org
URI: http://gettys.wordpress.com/
Jeffrey C. Mogul
Hewlett-Packard Company
HP Labs, Large Scale Systems Group
1501 Page Mill Road, MS 1177
Palo Alto, CA 94304
USA
EMail: JeffMogul@acm.org
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Henrik Frystyk Nielsen
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
USA
EMail: henrikn@microsoft.com
Larry Masinter
Adobe Systems, Incorporated
345 Park Ave
San Jose, CA 95110
USA
EMail: LMM@acm.org
URI: http://larry.masinter.net/
Paul J. Leach
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
EMail: paulle@microsoft.com
Tim Berners-Lee
World Wide Web Consortium
MIT Computer Science and Artificial Intelligence Laboratory
The Stata Center, Building 32
32 Vassar Street
Cambridge, MA 02139
USA
EMail: timbl@w3.org
URI: http://www.w3.org/People/Berners-Lee/
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Yves Lafon (editor)
World Wide Web Consortium
W3C / ERCIM
2004, rte des Lucioles
Sophia-Antipolis, AM 06902
France
EMail: ylafon@w3.org
URI: http://www.raubacapeu.net/people/yves/
Julian F. Reschke (editor)
greenbytes GmbH
Hafenweg 16
Muenster, NW 48155
Germany
Phone: +49 251 2807760
Fax: +49 251 2807761
EMail: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/
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