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Versions: 00 01 02 03 04 05 06 07 08 09 10 11
12 13 14 15 16 17 18 19 20 21 22 23
24 25 26 RFC 7231
Network Working Group R. Fielding, Ed.
Internet-Draft Day Software
Obsoletes: 2068, 2616 J. Gettys
(if approved) One Laptop per Child
Intended status: Standards Track J. Mogul
Expires: June 22, 2008 HP
H. Frystyk
Microsoft
L. Masinter
Adobe Systems
P. Leach
Microsoft
T. Berners-Lee
W3C/MIT
December 20, 2007
HTTP/1.1, part 2: Message Semantics
draft-ietf-httpbis-p2-semantics-00
Status of this Memo
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This Internet-Draft will expire on June 22, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2007).
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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)
This version of the HTTP specification contains only minimal
editorial changes from [RFC2616] (abstract, introductory paragraph,
and authors' addresses). All other changes are due to partitioning
the original into seven mostly independent parts. The intent is for
readers of future drafts to able to use draft 00 as the basis for
comparison when the WG makes later changes to the specification text.
This draft will shortly be followed by draft 01 (containing the first
round of changes that have already been agreed to on the mailing
list). There is no point in reviewing this draft other than to
verify that the partitioning has been done correctly. Roy T.
Fielding, Yves Lafon, and Julian Reschke will be the editors after
draft 00 is submitted.
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://www3.tools.ietf.org/wg/httpbis/trac/report/11> and related
documents (including fancy diffs) can be found at
<http://www3.tools.ietf.org/wg/httpbis/>.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Product Tokens . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Request Header Fields . . . . . . . . . . . . . . . . . . . . 6
5. Status Code and Reason Phrase . . . . . . . . . . . . . . . . 7
6. Response Header Fields . . . . . . . . . . . . . . . . . . . . 9
7. Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8. Method Definitions . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Safe and Idempotent Methods . . . . . . . . . . . . . . . 10
8.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . . 10
8.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . . 10
8.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.4. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.5. POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.6. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.8. TRACE . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.9. CONNECT . . . . . . . . . . . . . . . . . . . . . . . . . 16
9. Status Code Definitions . . . . . . . . . . . . . . . . . . . 16
9.1. Informational 1xx . . . . . . . . . . . . . . . . . . . . 16
9.1.1. 100 Continue . . . . . . . . . . . . . . . . . . . . . 16
9.1.2. 101 Switching Protocols . . . . . . . . . . . . . . . 17
9.2. Successful 2xx . . . . . . . . . . . . . . . . . . . . . . 17
9.2.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . . 17
9.2.2. 201 Created . . . . . . . . . . . . . . . . . . . . . 17
9.2.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . . 18
9.2.4. 203 Non-Authoritative Information . . . . . . . . . . 18
9.2.5. 204 No Content . . . . . . . . . . . . . . . . . . . . 18
9.2.6. 205 Reset Content . . . . . . . . . . . . . . . . . . 19
9.2.7. 206 Partial Content . . . . . . . . . . . . . . . . . 19
9.3. Redirection 3xx . . . . . . . . . . . . . . . . . . . . . 19
9.3.1. 300 Multiple Choices . . . . . . . . . . . . . . . . . 19
9.3.2. 301 Moved Permanently . . . . . . . . . . . . . . . . 20
9.3.3. 302 Found . . . . . . . . . . . . . . . . . . . . . . 20
9.3.4. 303 See Other . . . . . . . . . . . . . . . . . . . . 21
9.3.5. 304 Not Modified . . . . . . . . . . . . . . . . . . . 21
9.3.6. 305 Use Proxy . . . . . . . . . . . . . . . . . . . . 21
9.3.7. 306 (Unused) . . . . . . . . . . . . . . . . . . . . . 22
9.3.8. 307 Temporary Redirect . . . . . . . . . . . . . . . . 22
9.4. Client Error 4xx . . . . . . . . . . . . . . . . . . . . . 22
9.4.1. 400 Bad Request . . . . . . . . . . . . . . . . . . . 23
9.4.2. 401 Unauthorized . . . . . . . . . . . . . . . . . . . 23
9.4.3. 402 Payment Required . . . . . . . . . . . . . . . . . 23
9.4.4. 403 Forbidden . . . . . . . . . . . . . . . . . . . . 23
9.4.5. 404 Not Found . . . . . . . . . . . . . . . . . . . . 23
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9.4.6. 405 Method Not Allowed . . . . . . . . . . . . . . . . 23
9.4.7. 406 Not Acceptable . . . . . . . . . . . . . . . . . . 23
9.4.8. 407 Proxy Authentication Required . . . . . . . . . . 24
9.4.9. 408 Request Timeout . . . . . . . . . . . . . . . . . 24
9.4.10. 409 Conflict . . . . . . . . . . . . . . . . . . . . . 24
9.4.11. 410 Gone . . . . . . . . . . . . . . . . . . . . . . . 25
9.4.12. 411 Length Required . . . . . . . . . . . . . . . . . 25
9.4.13. 412 Precondition Failed . . . . . . . . . . . . . . . 25
9.4.14. 413 Request Entity Too Large . . . . . . . . . . . . . 25
9.4.15. 414 Request-URI Too Long . . . . . . . . . . . . . . . 26
9.4.16. 415 Unsupported Media Type . . . . . . . . . . . . . . 26
9.4.17. 416 Requested Range Not Satisfiable . . . . . . . . . 26
9.4.18. 417 Expectation Failed . . . . . . . . . . . . . . . . 26
9.5. Server Error 5xx . . . . . . . . . . . . . . . . . . . . . 26
9.5.1. 500 Internal Server Error . . . . . . . . . . . . . . 26
9.5.2. 501 Not Implemented . . . . . . . . . . . . . . . . . 27
9.5.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . . 27
9.5.4. 503 Service Unavailable . . . . . . . . . . . . . . . 27
9.5.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . . 27
9.5.6. 505 HTTP Version Not Supported . . . . . . . . . . . . 27
10. Header Field Definitions . . . . . . . . . . . . . . . . . . . 28
10.1. Allow . . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.2. Expect . . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.3. From . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
10.4. Location . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.5. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . . 30
10.6. Referer . . . . . . . . . . . . . . . . . . . . . . . . . 31
10.7. Retry-After . . . . . . . . . . . . . . . . . . . . . . . 31
10.8. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10.9. User-Agent . . . . . . . . . . . . . . . . . . . . . . . . 32
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
12. Security Considerations . . . . . . . . . . . . . . . . . . . 33
12.1. Transfer of Sensitive Information . . . . . . . . . . . . 33
12.2. Encoding Sensitive Information in URI's . . . . . . . . . 34
12.3. Location Headers and Spoofing . . . . . . . . . . . . . . 34
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 34
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Appendix A. Changes from RFC 2068 . . . . . . . . . . . . . . . . 36
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40
Intellectual Property and Copyright Statements . . . . . . . . . . 43
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1. Introduction
This document will define aspects of HTTP related to request and
response semantics. Right now it only includes the extracted
relevant sections of RFC 2616 with only minor edits.
The HTTP protocol is a request/response protocol. A client sends a
request to the server in the form of a request method, URI, and
protocol version, followed by a MIME-like message containing request
modifiers, client information, and possible body content over a
connection with a server. The server responds with a status line,
including the message's protocol version and a success or error code,
followed by a MIME-like message containing server information, entity
metainformation, and possible entity-body content. The relationship
between HTTP and MIME is described in Appendix A of [Part3].
2. Product Tokens
Product tokens are used to allow communicating applications to
identify themselves by software name and version. Most fields using
product tokens also allow sub-products which form a significant part
of the application to be listed, separated by white space. By
convention, the products are listed in order of their significance
for identifying the application.
product = token ["/" product-version]
product-version = token
Examples:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3
Server: Apache/0.8.4
Product tokens SHOULD be short and to the point. They MUST NOT be
used for advertising or other non-essential information. Although
any token character MAY appear in a product-version, this token
SHOULD only be used for a version identifier (i.e., successive
versions of the same product SHOULD only differ in the product-
version portion of the product value).
3. Method
The Method token indicates the method to be performed on the resource
identified by the Request-URI. The method is case-sensitive.
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Method = "OPTIONS" ; Section 8.2
| "GET" ; Section 8.3
| "HEAD" ; Section 8.4
| "POST" ; Section 8.5
| "PUT" ; Section 8.6
| "DELETE" ; Section 8.7
| "TRACE" ; Section 8.8
| "CONNECT" ; Section 8.9
| extension-method
extension-method = token
The list of methods allowed by a resource can be specified in an
Allow header field (Section 10.1). The return 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 return the status code 405 (Method Not
Allowed) if the method is known by the origin server but not allowed
for the requested 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 8.
4. 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.
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request-header = Accept ; [Part3], Section 5.1
| Accept-Charset ; [Part3], Section 5.2
| Accept-Encoding ; [Part3], Section 5.3
| Accept-Language ; [Part3], Section 5.4
| Authorization ; [Part7], Section 3.1
| Expect ; Section 10.2
| From ; Section 10.3
| Host ; [Part1], Section 8.4
| 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 10.5
| Proxy-Authorization ; [Part7], Section 3.3
| Range ; [Part5], Section 5.4
| Referer ; Section 10.6
| TE ; [Part1], Section 8.8
| User-Agent ; Section 10.9
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. Unrecognized header fields are treated as
entity-header fields.
5. 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. These codes are fully
defined in Section 9. 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's, 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 9.1.1: Continue
| "101" ; Section 9.1.2: Switching Protocols
| "200" ; Section 9.2.1: OK
| "201" ; Section 9.2.2: Created
| "202" ; Section 9.2.3: Accepted
| "203" ; Section 9.2.4: Non-Authoritative Information
| "204" ; Section 9.2.5: No Content
| "205" ; Section 9.2.6: Reset Content
| "206" ; Section 9.2.7: Partial Content
| "300" ; Section 9.3.1: Multiple Choices
| "301" ; Section 9.3.2: Moved Permanently
| "302" ; Section 9.3.3: Found
| "303" ; Section 9.3.4: See Other
| "304" ; Section 9.3.5: Not Modified
| "305" ; Section 9.3.6: Use Proxy
| "307" ; Section 9.3.8: Temporary Redirect
| "400" ; Section 9.4.1: Bad Request
| "401" ; Section 9.4.2: Unauthorized
| "402" ; Section 9.4.3: Payment Required
| "403" ; Section 9.4.4: Forbidden
| "404" ; Section 9.4.5: Not Found
| "405" ; Section 9.4.6: Method Not Allowed
| "406" ; Section 9.4.7: Not Acceptable
| "407" ; Section 9.4.8: Proxy Authentication Required
| "408" ; Section 9.4.9: Request Time-out
| "409" ; Section 9.4.10: Conflict
| "410" ; Section 9.4.11: Gone
| "411" ; Section 9.4.12: Length Required
| "412" ; Section 9.4.13: Precondition Failed
| "413" ; Section 9.4.14: Request Entity Too Large
| "414" ; Section 9.4.15: Request-URI Too Large
| "415" ; Section 9.4.16: Unsupported Media Type
| "416" ; Section 9.4.17: Requested range not satisfiable
| "417" ; Section 9.4.18: Expectation Failed
| "500" ; Section 9.5.1: Internal Server Error
| "501" ; Section 9.5.2: Not Implemented
| "502" ; Section 9.5.3: Bad Gateway
| "503" ; Section 9.5.4: Service Unavailable
| "504" ; Section 9.5.5: Gateway Time-out
| "505" ; Section 9.5.6: HTTP Version not supported
| extension-code
extension-code = 3DIGIT
Reason-Phrase = *<TEXT, excluding CR, LF>
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 entity returned
with the response, since that entity is likely to include human-
readable information which will explain the unusual status.
6. 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 resource identified by the Request-URI.
response-header = Accept-Ranges ; [Part5], Section 5.1
| Age ; [Part6], Section 3.1
| ETag ; [Part4], Section 6.1
| Location ; Section 10.4
| Proxy-Authenticate ; [Part7], Section 3.2
| Retry-After ; Section 10.7
| Server ; Section 10.8
| 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. Unrecognized header fields are treated as
entity-header fields.
7. Entity
Request and Response messages MAY transfer an entity if not otherwise
restricted by the request method or response status code. An entity
consists of entity-header fields and an entity-body, although some
responses will only include the entity-headers. HTTP entity-body and
entity-header fields are defined in [Part3].
An entity-body is only present in a message when a message-body is
present, as described in Section 4.3 of [Part1]. The entity-body is
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obtained from the message-body by decoding any Transfer-Encoding that
might have been applied to ensure safe and proper transfer of the
message.
8. 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.
The Host request-header field (Section 8.4 of [Part1]) MUST accompany
all HTTP/1.1 requests.
8.1. Safe and Idempotent Methods
8.1.1. Safe Methods
Implementors should be aware that the software represents the user in
their interactions over the Internet, and should be careful to allow
the user to be aware of any actions they might take which may have an
unexpected significance to themselves or others.
In particular, the convention has been established that the GET and
HEAD 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.
8.1.2. Idempotent Methods
Methods can also have the property of "idempotence" in that (aside
from error or expiration issues) the side-effects of N > 0 identical
requests is the same as for a single request. The methods GET, HEAD,
PUT and DELETE share this property. Also, the methods OPTIONS and
TRACE SHOULD NOT have side effects, and so are inherently idempotent.
However, it is possible that a sequence of several requests is non-
idempotent, even if all of the methods executed in that sequence are
idempotent. (A sequence is idempotent if a single execution of the
entire sequence always yields a result that is not changed by a
reexecution of all, or part, of that sequence.) For example, a
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sequence is non-idempotent if its result depends on a value that is
later modified in the same sequence.
A sequence that never has side effects is idempotent, by definition
(provided that no concurrent operations are being executed on the
same set of resources).
8.2. OPTIONS
The OPTIONS method represents a request for information about the
communication options available on the request/response chain
identified by the 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 an entity-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. A server that does not support such an
extension MAY discard the request body.
If the Request-URI 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-URI 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".
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The Max-Forwards request-header field MAY be used to target a
specific proxy in the request chain. When a proxy receives an
OPTIONS request on an absoluteURI for which request forwarding is
permitted, the proxy MUST check for a Max-Forwards field. If the
Max-Forwards field-value is zero ("0"), the proxy MUST NOT forward
the message; instead, the proxy SHOULD respond with its own
communication options. If the Max-Forwards field-value is an integer
greater than zero, the proxy MUST decrement the field-value when it
forwards the request. If no Max-Forwards field is present in the
request, then the forwarded request MUST NOT include a Max-Forwards
field.
8.3. GET
The GET method means retrieve whatever information (in the form of an
entity) is identified by the Request-URI. If the Request-URI refers
to a data-producing process, it is the produced data which shall be
returned as the entity 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 entity 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 entities 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 entity 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 entities to
be completed without transferring data already held by the client.
The response to a GET request is cacheable if and only if it meets
the requirements for HTTP caching described in [Part6].
See Section 12.2 for security considerations when used for forms.
8.4. HEAD
The HEAD method is identical to GET except that the server MUST NOT
return a message-body in the response. The metainformation 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 metainformation about the entity implied by
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the request without transferring the entity-body itself. This method
is often used for testing hypertext links for validity,
accessibility, and recent modification.
The response to a HEAD request MAY be cacheable in the sense that the
information contained in the response MAY be used to update a
previously cached entity from that resource. If the new field values
indicate that the cached entity differs from the current entity (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.
8.5. POST
The POST method is used to request that the origin server accept the
entity enclosed in the request as a new subordinate of the resource
identified by the Request-URI in the Request-Line. 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 Request-URI. The posted
entity is subordinate to that URI in the same way that a file is
subordinate to a directory containing it, a news article is
subordinate to a newsgroup to which it is posted, or a record is
subordinate to a database.
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,
depending on whether or not the response includes an entity that
describes the result.
If a resource has been created on the origin server, the response
SHOULD be 201 (Created) and contain an entity which describes the
status of the request and refers to the new resource, and a Location
header (see Section 10.4).
Responses to this method are not cacheable, unless the response
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includes appropriate Cache-Control or Expires header fields.
However, the 303 (See Other) response can be used to direct the user
agent to retrieve a cacheable resource.
POST requests MUST obey the message transmission requirements set out
in Section 7.2 of [Part1].
See Section 12.2 for security considerations.
8.6. PUT
The PUT method requests that the enclosed entity be stored under the
supplied Request-URI. If the Request-URI refers to an already
existing resource, the enclosed entity SHOULD be considered as a
modified version of the one residing on the origin server. If the
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, 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 resource
could not be created or modified with the Request-URI, an appropriate
error response SHOULD be given that reflects the nature of the
problem. The recipient of the entity MUST NOT ignore any Content-*
(e.g. Content-Range) headers 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 and the Request-URI identifies
one or more currently cached entities, those entries SHOULD be
treated as stale. Responses to this method are not cacheable.
The fundamental difference between the POST and PUT requests is
reflected in the different meaning of the Request-URI. The URI in a
POST request identifies the resource that will handle the enclosed
entity. That resource might be a data-accepting process, a gateway
to some other protocol, or a separate entity that accepts
annotations. In contrast, the URI in a PUT request identifies the
entity enclosed with the request -- 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
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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.
HTTP/1.1 does not define how a PUT method affects the state of an
origin server.
PUT requests MUST obey the message transmission requirements set out
in Section 7.2 of [Part1].
Unless otherwise specified for a particular entity-header, the
entity-headers in the PUT request SHOULD be applied to the resource
created or modified by the PUT.
8.7. DELETE
The DELETE method requests that the origin server delete the resource
identified by the Request-URI. 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
entity 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 an entity.
If the request passes through a cache and the Request-URI identifies
one or more currently cached entities, those entries SHOULD be
treated as stale. Responses to this method are not cacheable.
8.8. 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 entity-
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 10.5). A TRACE request
MUST NOT include an entity.
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 8.9 of
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[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 contain the entire
request message in the entity-body, with a Content-Type of "message/
http". Responses to this method MUST NOT be cached.
8.9. 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 [Luo1998]).
9. Status Code Definitions
Each Status-Code is described below, including a description of which
method(s) it can follow and any metainformation required in the
response.
9.1. 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).)
9.1.1. 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
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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.
9.1.2. 101 Switching Protocols
The server understands and is willing to comply with the client's
request, via the Upgrade message header field (Section 5.4 of
[Part5]), 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.
9.2. Successful 2xx
This class of status code indicates that the client's request was
successfully received, understood, and accepted.
9.2.1. 200 OK
The request has succeeded. The information returned with the
response is dependent on the method used in the request, for example:
GET an entity corresponding to the requested resource is sent in the
response;
HEAD the entity-header fields corresponding to the requested
resource are sent in the response without any message-body;
POST an entity describing or containing the result of the action;
TRACE an entity containing the request message as received by the
end server.
9.2.2. 201 Created
The request has been fulfilled and resulted in a new resource being
created. The newly created resource can be referenced by the URI(s)
returned in the entity of the response, with the most specific URI
for the resource given by a Location header field. The response
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SHOULD include an entity containing a list of resource
characteristics and location(s) from which the user or user agent can
choose the one most appropriate. The entity format is specified by
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 requested variant just
created, see Section 6.1 of [Part4].
9.2.3. 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 entity 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.
9.2.4. 203 Non-Authoritative Information
The returned metainformation in the entity-header 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 metainformation 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).
9.2.5. 204 No Content
The server has fulfilled the request but does not need to return an
entity-body, and might want to return updated metainformation. The
response MAY include new or updated metainformation in the form of
entity-headers, which if present SHOULD be associated with the
requested variant.
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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 metainformation 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.
9.2.6. 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 an entity.
9.2.7. 206 Partial Content
The server has fulfilled the partial GET request for the resource and
the enclosed entity is a partial representation as defined in
[Part5].
9.3. 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
GET or HEAD. A client SHOULD detect infinite redirection loops,
since such loops generate network traffic for each redirection.
Note: previous versions of this specification recommended a
maximum of five redirections. Content developers should be aware
that there might be clients that implement such a fixed
limitation.
9.3.1. 300 Multiple Choices
The requested resource corresponds to any one of a set of
representations, each with its own specific location, and agent-
driven negotiation information (Section 4 of [Part3]) is being
provided so that the user (or user agent) can select a preferred
representation and redirect its request to that location.
Unless it was a HEAD request, the response SHOULD include an entity
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containing a list of resource characteristics and location(s) from
which the user or user agent can choose the one most appropriate.
The entity 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. This response is cacheable unless indicated otherwise.
9.3.2. 301 Moved Permanently
The requested 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 Request-URI to one or more of the new
references returned by the server, where possible. This response is
cacheable unless indicated otherwise.
The new permanent URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the entity 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 other
than GET or HEAD, 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: 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.
9.3.3. 302 Found
The requested resource resides temporarily under a different URI.
Since the redirection might be altered on occasion, the client SHOULD
continue to use the Request-URI for future requests. This response
is only cacheable if indicated by a Cache-Control or Expires header
field.
The temporary URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the entity of the
response SHOULD contain a short hypertext note with a hyperlink to
the new URI(s).
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If the 302 status code is received in response to a request other
than GET or HEAD, 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: RFC 1945 and RFC 2068 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. The status codes 303 and 307 have
been added for servers that wish to make unambiguously clear which
kind of reaction is expected of the client.
9.3.4. 303 See Other
The response to the request can be found under a different URI and
SHOULD be retrieved using a GET method on that resource. This method
exists primarily to allow the output of a POST-activated script to
redirect the user agent to a selected resource. The new URI is not a
substitute reference for the originally requested resource. The 303
response MUST NOT be cached, but the response to the second
(redirected) request might be cacheable.
The different URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the entity of the
response SHOULD contain a short hypertext note with a hyperlink to
the new URI(s).
Note: Many pre-HTTP/1.1 user agents do not understand the 303
status. When interoperability with such clients is a concern, the
302 status code may be used instead, since most user agents react
to a 302 response as described here for 303.
9.3.5. 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 [Part4].
9.3.6. 305 Use Proxy
The requested resource MUST be accessed through the proxy given by
the Location field. The Location field gives the URI of the proxy.
The recipient is expected to repeat this single request via the
proxy. 305 responses MUST only be generated by origin servers.
Note: RFC 2068 was not clear that 305 was intended to redirect a
single request, and to be generated by origin servers only. Not
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observing these limitations has significant security consequences.
9.3.7. 306 (Unused)
The 306 status code was used in a previous version of the
specification, is no longer used, and the code is reserved.
9.3.8. 307 Temporary Redirect
The requested resource resides temporarily under a different URI.
Since the redirection MAY be altered on occasion, the client SHOULD
continue to use the Request-URI for future requests. This response
is only cacheable if indicated by a Cache-Control or Expires header
field.
The temporary URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the entity 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. 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 other
than GET or HEAD, 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.
9.4. 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 an entity 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 entity 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 may erase the client's unacknowledged input buffers
before they can be read and interpreted by the HTTP application.
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9.4.1. 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.
9.4.2. 401 Unauthorized
The request requires user authentication (see [Part7]).
9.4.3. 402 Payment Required
This code is reserved for future use.
9.4.4. 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 entity. If the server does not wish to
make this information available to the client, the status code 404
(Not Found) can be used instead.
9.4.5. 404 Not Found
The server has not found anything matching the 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.
9.4.6. 405 Method Not Allowed
The method specified in the Request-Line is not allowed for the
resource identified by the Request-URI. The response MUST include an
Allow header containing a list of valid methods for the requested
resource.
9.4.7. 406 Not Acceptable
The resource identified by the request is only capable of generating
response entities which have content characteristics not acceptable
according to the accept headers sent in the request.
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Unless it was a HEAD request, the response SHOULD include an entity
containing a list of available entity characteristics and location(s)
from which the user or user agent can choose the one most
appropriate. The entity 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 may 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.
9.4.8. 407 Proxy Authentication Required
This code is similar to 401 (Unauthorized), but indicates that the
client must first authenticate itself with the proxy (see [Part7]).
9.4.9. 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.
9.4.10. 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 entity 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 entity 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 entity would likely contain a list of the differences
between the two versions in a format defined by the response Content-
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Type.
9.4.11. 410 Gone
The requested 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 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. This response is cacheable unless indicated otherwise.
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.
9.4.12. 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.
9.4.13. 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
[Part4].
9.4.14. 413 Request Entity Too Large
The server is refusing to process a request because the request
entity 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.
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9.4.15. 414 Request-URI Too Long
The server is refusing to service the request because the 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 Request-URI.
9.4.16. 415 Unsupported Media Type
The server is refusing to service the request because the entity of
the request is in a format not supported by the requested resource
for the requested method.
9.4.17. 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.
9.4.18. 417 Expectation Failed
The expectation given in an Expect request-header field (see
Section 10.2) 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.
9.5. 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 an entity containing an explanation of the
error situation, and whether it is a temporary or permanent
condition. User agents SHOULD display any included entity to the
user. These response codes are applicable to any request method.
9.5.1. 500 Internal Server Error
The server encountered an unexpected condition which prevented it
from fulfilling the request.
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9.5.2. 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.
9.5.3. 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.
9.5.4. 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 may
wish to simply refuse the connection.
9.5.5. 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: Note to implementors: some deployed proxies are known to
return 400 or 500 when DNS lookups time out.
9.5.6. 505 HTTP Version Not Supported
The server does not support, or refuses to support, the HTTP 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
3.1 of [Part1], other than with this error message. The response
SHOULD contain an entity describing why that version is not supported
and what other protocols are supported by that server.
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10. Header Field Definitions
This section defines the syntax and semantics of all standard
HTTP/1.1 header fields. For entity-header fields, both sender and
recipient refer to either the client or the server, depending on who
sends and who receives the entity.
10.1. Allow
The Allow entity-header field lists the set of methods supported by
the resource identified by the Request-URI. The purpose of this
field is strictly to inform the recipient of valid methods associated
with the resource. An Allow header field MUST be present in a 405
(Method Not Allowed) response.
Allow = "Allow" ":" #Method
Example of use:
Allow: GET, HEAD, PUT
This field cannot prevent a client from trying other methods.
However, the indications given by the Allow header field value SHOULD
be followed. The actual set of allowed methods is defined by the
origin server at the time of each request.
The Allow header field MAY be provided with a PUT request to
recommend the methods to be supported by the new or modified
resource. The server is not required to support these methods and
SHOULD include an Allow header in the response giving the actual
supported methods.
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.
10.2. Expect
The Expect request-header field is used to indicate that particular
server behaviors are required by the client.
Expect = "Expect" ":" 1#expectation
expectation = "100-continue" | expectation-extension
expectation-extension = token [ "=" ( token | quoted-string )
*expect-params ]
expect-params = ";" token [ "=" ( token | quoted-string ) ]
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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. The server MUST respond with a 417
(Expectation Failed) status if any of the expectations cannot be met
or, if there are other problems with the request, some other 4xx
status.
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.
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 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.
10.3. 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 RFC 822 [RFC822] as updated by RFC 1123 [RFC1123]:
From = "From" ":" mailbox
An example is:
From: webmaster@w3.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
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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.
10.4. Location
The Location response-header field is used to redirect the recipient
to a location other than the Request-URI for completion of the
request or identification of a new resource. For 201 (Created)
responses, the Location is that 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 absolute URI.
Location = "Location" ":" absoluteURI
An example is:
Location: http://www.w3.org/pub/WWW/People.html
Note: The Content-Location header field (Section 5.7 of [Part3])
differs from Location in that the Content-Location identifies the
original location of the entity enclosed in the request. It is
therefore possible for a response to contain header fields for
both Location and Content-Location.
10.5. Max-Forwards
The Max-Forwards request-header field provides a mechanism with the
TRACE (Section 8.8) and OPTIONS (Section 8.2) methods to limit the
number of proxies or gateways that can forward the request to the
next inbound server. This can be useful when the client is
attempting to trace a request chain which appears to be failing or
looping in mid-chain.
Max-Forwards = "Max-Forwards" ":" 1*DIGIT
The Max-Forwards value is a decimal integer indicating the remaining
number of times this request message may be forwarded.
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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
defined by this specification and for any extension methods for which
it is not explicitly referred to as part of that method definition.
10.6. Referer
The Referer[sic] request-header field allows the client to specify,
for the server's benefit, the address (URI) of the resource from
which the Request-URI was obtained (the "referrer", although the
header field is misspelled.) The Referer request-header allows a
server 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. The Referer field MUST NOT be
sent if the Request-URI was obtained from a source that does not have
its own URI, such as input from the user keyboard.
Referer = "Referer" ":" ( absoluteURI | relativeURI )
Example:
Referer: http://www.w3.org/hypertext/DataSources/Overview.html
If the field value is a relative URI, it SHOULD be interpreted
relative to the Request-URI. The URI MUST NOT include a fragment.
See Section 12.2 for security considerations.
10.7. Retry-After
The Retry-After response-header 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" ":" ( HTTP-date | delta-seconds )
Two examples of its use are
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Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
Retry-After: 120
In the latter example, the delay is 2 minutes.
10.8. 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 2) and comments
identifying the server and any significant subproducts. The product
tokens are listed in order of their significance for identifying the
application.
Server = "Server" ":" 1*( 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
SHOULD include a Via field (as described in Section 8.9 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.
10.9. 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. User agents SHOULD include
this field with requests. The field can contain multiple product
tokens (Section 2) and comments 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" ":" 1*( product | comment )
Example:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3
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11. IANA Considerations
TBD.
12. 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.
12.1. 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
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.
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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 10.9) or Server (Section 10.8) 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.
12.2. Encoding Sensitive Information in URI's
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 which use the HTTP protocol SHOULD NOT use GET
based forms for the submission of sensitive data, because this will
cause this data to be encoded in the Request-URI. Many existing
servers, proxies, and user agents will log the request URI in some
place where it might be visible to third parties. Servers can use
POST-based form submission instead
12.3. 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.
13. Acknowledgments
Based on an XML translation of RFC 2616 by Julian Reschke.
14. References
[Luo1998] Luotonen, A., "Tunneling TCP based protocols through Web
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Internet-Draft HTTP/1.1 December 2007
proxy servers", Work in Progress.
[Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "HTTP/1.1,
part 1: URIs, Connections, and Message Parsing",
draft-ietf-httpbis-p1-messaging-00 (work in progress),
December 2007.
[Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "HTTP/1.1,
part 3: Message Payload and Content Negotiation",
draft-ietf-httpbis-p3-payload-00 (work in progress),
December 2007.
[Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "HTTP/1.1,
part 4: Conditional Requests",
draft-ietf-httpbis-p4-conditional-00 (work in progress),
December 2007.
[Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "HTTP/1.1,
part 5: Range Requests and Partial Responses",
draft-ietf-httpbis-p5-range-00 (work in progress),
December 2007.
[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "HTTP/1.1,
part 6: Caching", draft-ietf-httpbis-p6-cache-00 (work in
progress), December 2007.
[Part7] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "HTTP/1.1,
part 7: Authentication", draft-ietf-httpbis-p7-auth-00
(work in progress), December 2007.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989.
[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.
[RFC822] Crocker, D., "Standard for the format of ARPA Internet
Fielding, et al. Expires June 22, 2008 [Page 35]
Internet-Draft HTTP/1.1 December 2007
text messages", STD 11, RFC 822, August 1982.
Appendix A. Changes from RFC 2068
Clarified which error code should be used for inbound server failures
(e.g. DNS failures). (Section 9.5.5).
CREATE had a race that required an Etag be sent when a resource is
first created. (Section 9.2.2).
Rewrite of message transmission requirements to make it much harder
for implementors to get it wrong, as the consequences of errors here
can have significant impact on the Internet, and to deal with the
following problems:
1. Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
this was incorrectly placing a requirement on the behavior of an
implementation of a future version of HTTP/1.x
2. Made it clear that user-agents should retry requests, not
"clients" in general.
3. Converted requirements for clients to ignore unexpected 100
(Continue) responses, and for proxies to forward 100 responses,
into a general requirement for 1xx responses.
4. Modified some TCP-specific language, to make it clearer that non-
TCP transports are possible for HTTP.
5. Require that the origin server MUST NOT wait for the request body
before it sends a required 100 (Continue) response.
6. Allow, rather than require, a server to omit 100 (Continue) if it
has already seen some of the request body.
7. Allow servers to defend against denial-of-service attacks and
broken clients.
This change adds the Expect header and 417 status code.
Clean up confusion between 403 and 404 responses. (Section 9.4.4,
9.4.5, and 9.4.11)
The PATCH, LINK, UNLINK methods were defined but not commonly
implemented in previous versions of this specification. See RFC 2068
[RFC2068].
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Index
1
100 Continue (status code) 16
101 Switching Protocols (status code) 17
2
200 OK (status code) 17
201 Created (status code) 17
202 Accepted (status code) 18
203 Non-Authoritative Information (status code) 18
204 No Content (status code) 18
205 Reset Content (status code) 19
206 Partial Content (status code) 19
3
300 Multiple Choices (status code) 19
301 Moved Permanently (status code) 20
302 Found (status code) 20
303 See Other (status code) 21
304 Not Modified (status code) 21
305 Use Proxy (status code) 21
306 (Unused) (status code) 22
307 Temporary Redirect (status code) 22
4
400 Bad Request (status code) 23
401 Unauthorized (status code) 23
402 Payment Required (status code) 23
403 Forbidden (status code) 23
404 Not Found (status code) 23
405 Method Not Allowed (status code) 23
406 Not Acceptable (status code) 23
407 Proxy Authentication Required (status code) 24
408 Request Timeout (status code) 24
409 Conflict (status code) 24
410 Gone (status code) 25
411 Length Required (status code) 25
412 Precondition Failed (status code) 25
413 Request Entity Too Large (status code) 25
414 Request-URI Too Long (status code) 26
415 Unsupported Media Type (status code) 26
416 Requested Range Not Satisfiable (status code) 26
417 Expectation Failed (status code) 26
5
500 Internal Server Error (status code) 26
501 Not Implemented (status code) 27
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502 Bad Gateway (status code) 27
503 Service Unavailable (status code) 27
504 Gateway Timeout (status code) 27
505 HTTP Version Not Supported (status code) 27
A
Allow header 28
C
CONNECT method 16
D
DELETE method 15
E
Expect header 28
F
From header 29
G
GET method 12
Grammar
Allow 28
Expect 28
expect-params 28
expectation 28
expectation-extension 28
extension-code 8
extension-method 6
From 29
Location 30
Max-Forwards 30
Method 6
product 5
product-version 5
Reason-Phrase 8
Referer 31
request-header 7
response-header 9
Retry-After 31
Server 32
Status-Code 8
User-Agent 32
H
HEAD method 12
Headers
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Allow 28
Expect 28
From 29
Location 30
Max-Forwards 30
Referer 31
Retry-After 31
Server 32
User-Agent 32
L
LINK method 36
Location header 30
M
Max-Forwards header 30
Methods
CONNECT 16
DELETE 15
GET 12
HEAD 12
LINK 36
OPTIONS 11
PATCH 36
POST 13
PUT 14
TRACE 15
UNLINK 36
O
OPTIONS method 11
P
PATCH method 36
POST method 13
PUT method 14
R
Referer header 31
Retry-After header 31
S
Server header 32
Status Codes
100 Continue 16
101 Switching Protocols 17
200 OK 17
201 Created 17
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202 Accepted 18
203 Non-Authoritative Information 18
204 No Content 18
205 Reset Content 19
206 Partial Content 19
300 Multiple Choices 19
301 Moved Permanently 20
302 Found 20
303 See Other 21
304 Not Modified 21
305 Use Proxy 21
306 (Unused) 22
307 Temporary Redirect 22
400 Bad Request 23
401 Unauthorized 23
402 Payment Required 23
403 Forbidden 23
404 Not Found 23
405 Method Not Allowed 23
406 Not Acceptable 23
407 Proxy Authentication Required 24
408 Request Timeout 24
409 Conflict 24
410 Gone 25
411 Length Required 25
412 Precondition Failed 25
413 Request Entity Too Large 25
414 Request-URI Too Long 26
415 Unsupported Media Type 26
416 Requested Range Not Satisfiable 26
417 Expectation Failed 26
500 Internal Server Error 26
501 Not Implemented 27
502 Bad Gateway 27
503 Service Unavailable 27
504 Gateway Timeout 27
505 HTTP Version Not Supported 27
T
TRACE method 15
U
UNLINK method 36
User-Agent header 32
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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
One Laptop per Child
21 Oak Knoll Road
Carlisle, MA 01741
USA
Email: jg@laptop.org
URI: http://www.laptop.org/
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
Henrik Frystyk Nielsen
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
USA
Email: henrikn@microsoft.com
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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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Full Copyright Statement
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Fielding, et al. Expires June 22, 2008 [Page 43]
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