One document matched: draft-ietf-httpbis-p2-semantics-13.xml
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<rfc obsoletes="2616" updates="2817" category="std" ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-13">
<front>
<title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address>
<postal>
<street>345 Park Ave</street>
<city>San Jose</city>
<region>CA</region>
<code>95110</code>
<country>USA</country>
</postal>
<email>fielding@gbiv.com</email>
<uri>http://roy.gbiv.com/</uri>
</address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address>
<postal>
<street>21 Oak Knoll Road</street>
<city>Carlisle</city>
<region>MA</region>
<code>01741</code>
<country>USA</country>
</postal>
<email>jg@freedesktop.org</email>
<uri>http://gettys.wordpress.com/</uri>
</address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address>
<postal>
<street>HP Labs, Large Scale Systems Group</street>
<street>1501 Page Mill Road, MS 1177</street>
<city>Palo Alto</city>
<region>CA</region>
<code>94304</code>
<country>USA</country>
</postal>
<email>JeffMogul@acm.org</email>
</address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address>
<postal>
<street>1 Microsoft Way</street>
<city>Redmond</city>
<region>WA</region>
<code>98052</code>
<country>USA</country>
</postal>
<email>henrikn@microsoft.com</email>
</address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address>
<postal>
<street>345 Park Ave</street>
<city>San Jose</city>
<region>CA</region>
<code>95110</code>
<country>USA</country>
</postal>
<email>LMM@acm.org</email>
<uri>http://larry.masinter.net/</uri>
</address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address>
<postal>
<street>1 Microsoft Way</street>
<city>Redmond</city>
<region>WA</region>
<code>98052</code>
</postal>
<email>paulle@microsoft.com</email>
</address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address>
<postal>
<street>MIT Computer Science and Artificial Intelligence Laboratory</street>
<street>The Stata Center, Building 32</street>
<street>32 Vassar Street</street>
<city>Cambridge</city>
<region>MA</region>
<code>02139</code>
<country>USA</country>
</postal>
<email>timbl@w3.org</email>
<uri>http://www.w3.org/People/Berners-Lee/</uri>
</address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address>
<postal>
<street>W3C / ERCIM</street>
<street>2004, rte des Lucioles</street>
<city>Sophia-Antipolis</city>
<region>AM</region>
<code>06902</code>
<country>France</country>
</postal>
<email>ylafon@w3.org</email>
<uri>http://www.raubacapeu.net/people/yves/</uri>
</address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address>
<postal>
<street>Hafenweg 16</street>
<city>Muenster</city><region>NW</region><code>48155</code>
<country>Germany</country>
</postal>
<phone>+49 251 2807760</phone>
<facsimile>+49 251 2807761</facsimile>
<email>julian.reschke@greenbytes.de</email>
<uri>http://greenbytes.de/tech/webdav/</uri>
</address>
</author>
<date month="March" year="2011" day="14"/>
<workgroup>HTTPbis Working Group</workgroup>
<abstract>
<t>
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.
</t>
</abstract>
<note title="Editorial Note (To be removed by RFC Editor)">
<t>
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 <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
and related documents (including fancy diffs) can be found at
<eref target="http://tools.ietf.org/wg/httpbis/"/>.
</t>
<t>
The changes in this draft are summarized in <xref target="changes.since.12"/>.
</t>
</note>
</front>
<middle>
<section title="Introduction" anchor="introduction">
<t>
This document defines HTTP/1.1 request and response semantics. Each HTTP
message, as defined in <xref target="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.
</t>
<t>
This document is currently disorganized in order to minimize the changes
between drafts and enable reviewers to see the smaller errata changes.
A future 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, methods, request modifying header fields, response status,
status modifying header fields, and resource metadata. The current mess
reflects how widely dispersed these topics and associated requirements
had become in <xref target="RFC2616"/>.
</t>
<section title="Requirements" anchor="intro.requirements">
<t>
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 <xref target="RFC2119"/>.
</t>
<t>
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".
</t>
</section>
<section title="Syntax Notation" anchor="notation">
<t>
This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
extends the syntax defined in <xref target="RFC5234"/> with a list rule).
<xref target="collected.abnf"/> shows the collected ABNF, with the list
rule expanded.
</t>
<t>
The following core rules are included by
reference, as defined in <xref target="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 sequence of data), SP (space),
VCHAR (any visible USASCII character),
and WSP (whitespace).
</t>
<section title="Core Rules" anchor="core.rules">
<t>
The core rules below are defined in Section 1.2.2 of <xref target="Part1"/>:
</t>
<figure><artwork type="abnf2616"><![CDATA[
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>
]]></artwork></figure>
</section>
<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
<t>
The ABNF rules below are defined in other parts:
</t>
<figure><artwork type="abnf2616"><![CDATA[
absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
comment = <comment, defined in [Part1], Section 3.2>
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>
URI-reference = <URI-reference, defined in [Part1], Section 2.6>
]]></artwork></figure>
</section>
</section>
</section>
<section title="Method" anchor="method">
<t>
The Method token indicates the request method to be performed on the target
resource (Section 4.3 of <xref target="Part1"/>). The method is case-sensitive.
</t>
<figure><iref primary="true" item="Grammar" subitem="Method"/><artwork type="abnf2616"><![CDATA[
Method = token
]]></artwork></figure>
<t>
The list of methods allowed by a resource can be specified in an
Allow header field (<xref target="header.allow"/>). 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 <xref target="method.definitions"/>.
</t>
<section title="Overview of Methods" anchor="overview.of.methods">
<t>
The methods listed below are defined in <xref target="method.definitions"/>.
</t>
<texttable align="left">
<ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
<c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
<c>GET</c> <c><xref target="GET"/></c>
<c>HEAD</c> <c><xref target="HEAD"/></c>
<c>POST</c> <c><xref target="POST"/></c>
<c>PUT</c> <c><xref target="PUT"/></c>
<c>DELETE</c> <c><xref target="DELETE"/></c>
<c>TRACE</c> <c><xref target="TRACE"/></c>
<c>CONNECT</c> <c><xref target="CONNECT"/></c>
</texttable>
<t>
Note that this list is not exhaustive — it does not include request methods defined
in other specifications.
</t>
</section>
<section title="Method Registry" anchor="method.registry">
<t>
The HTTP Method Registry defines the name space for the Method token in the
Request line of an HTTP request.
</t>
<t>
Registrations MUST include the following fields:
<list style="symbols">
<t>Method Name (see <xref target="method"/>)</t>
<t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
<t>Pointer to specification text</t>
</list>
</t>
<t>
Values to be added to this name space are subject to IETF review
(<xref target="RFC5226"/>, Section 4.1).
</t>
<t>
The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
</t>
<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
<t>
When it is necessary to express new semantics for a HTTP request that
aren't specific to a single application or media type, and currently defined
methods are inadequate, it may be appropriate to register a new method.
</t>
<t>
HTTP methods are generic; that is, they are potentially applicable to any
resource, not just one particular media type, "type" of resource, or
application. As such, it is preferred that new HTTP methods be registered
in a document that isn't specific to a single application, so that this is
clear.
</t>
<t>
Due to the parsing rules defined in Section 3.3 of <xref target="Part1"/>, definitions of HTTP
methods cannot prohibit the presence of a message-body on either the request
or the response message (with responses to HEAD requests being the single
exception). Definitions of new methods cannot change this rule, but they can
specify that only zero-length bodies (as opposed to absent bodies) are allowed.
</t>
<t>
New method definitions need to indicate whether they are safe (<xref target="safe.methods"/>) and whether they are idempotent (<xref target="idempotent.methods"/>). They also need to state whether they can be
cached (<xref target="Part6"/>); in particular what conditions a cache may store the
response, and under what conditions such a stored response may be used to
satisfy a subsequent request.
</t>
</section>
</section>
</section>
<section title="Request Header Fields" anchor="request.header.fields">
<t>
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.
</t>
<texttable align="left">
<ttcol>Header Field Name</ttcol>
<ttcol>Defined in...</ttcol>
<c>Accept</c> <c>Section 6.1 of <xref target="Part3"/></c>
<c>Accept-Charset</c> <c>Section 6.2 of <xref target="Part3"/></c>
<c>Accept-Encoding</c> <c>Section 6.3 of <xref target="Part3"/></c>
<c>Accept-Language</c> <c>Section 6.4 of <xref target="Part3"/></c>
<c>Authorization</c> <c>Section 4.1 of <xref target="Part7"/></c>
<c>Expect</c> <c><xref target="header.expect"/></c>
<c>From</c> <c><xref target="header.from"/></c>
<c>Host</c> <c>Section 9.4 of <xref target="Part1"/></c>
<c>If-Match</c> <c>Section 6.2 of <xref target="Part4"/></c>
<c>If-Modified-Since</c> <c>Section 6.3 of <xref target="Part4"/></c>
<c>If-None-Match</c> <c>Section 6.4 of <xref target="Part4"/></c>
<c>If-Range</c> <c>Section 5.3 of <xref target="Part5"/></c>
<c>If-Unmodified-Since</c> <c>Section 6.5 of <xref target="Part4"/></c>
<c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
<c>Proxy-Authorization</c> <c>Section 4.3 of <xref target="Part7"/></c>
<c>Range</c> <c>Section 5.4 of <xref target="Part5"/></c>
<c>Referer</c> <c><xref target="header.referer"/></c>
<c>TE</c> <c>Section 9.5 of <xref target="Part1"/></c>
<c>User-Agent</c> <c><xref target="header.user-agent"/></c>
</texttable>
</section>
<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
<t>
The Status-Code element is a 3-digit integer result code of the attempt to
understand and satisfy the request.
</t>
<t>
The Reason-Phrase is intended to give a short textual description of the
Status-Code and is intended for a human user. The client does not need
to examine or display the Reason-Phrase.
</t>
<figure><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="extension-code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/><artwork type="abnf2616"><![CDATA[
Status-Code = 3DIGIT
Reason-Phrase = *( WSP / VCHAR / obs-text )
]]></artwork></figure>
<t>
HTTP status codes are extensible. HTTP applications are not required
to understand the meaning of all registered status codes, though such
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.
</t>
<section title="Overview of Status Codes" anchor="overview.of.status.codes">
<t>
The status codes listed below are defined in <xref target="status.codes"/>
of this specification, Section 3 of <xref target="Part4"/>, Section 3 of <xref target="Part5"/>, and Section 3 of <xref target="Part7"/>.
The reason phrases listed here are only recommendations — they can be
replaced by local equivalents without affecting the protocol.
</t>
<texttable align="left">
<ttcol>Status-Code</ttcol>
<ttcol>Reason-Phrase</ttcol>
<ttcol>Defined in...</ttcol>
<c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
<c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
<c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
<c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
<c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
<c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
<c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
<c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
<c>206</c> <c>Partial Content</c> <c>Section 3.1 of <xref target="Part5"/></c>
<c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
<c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
<c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
<c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
<c>304</c> <c>Not Modified</c> <c>Section 3.1 of <xref target="Part4"/></c>
<c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
<c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
<c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
<c>401</c> <c>Unauthorized</c> <c>Section 3.1 of <xref target="Part7"/></c>
<c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
<c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
<c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
<c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
<c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
<c>407</c> <c>Proxy Authentication Required</c> <c>Section 3.2 of <xref target="Part7"/></c>
<c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
<c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
<c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
<c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
<c>412</c> <c>Precondition Failed</c> <c>Section 3.2 of <xref target="Part4"/></c>
<c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
<c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
<c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
<c>416</c> <c>Requested range not satisfiable</c> <c>Section 3.2 of <xref target="Part5"/></c>
<c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
<c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
<c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
<c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
<c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
<c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
<c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
<c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
</texttable>
<t>
Note that this list is not exhaustive — it does not include
extension status codes defined in other specifications.
</t>
</section>
<section title="Status Code Registry" anchor="status.code.registry">
<t>
The HTTP Status Code Registry defines the name space for the Status-Code
token in the Status-Line of an HTTP response.
</t>
<t>
Values to be added to this name space are subject to IETF review
(<xref target="RFC5226"/>, Section 4.1).
</t>
<t>
The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
</t>
<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
<t>
When it is necessary to express new semantics for a HTTP response that
aren't specific to a single application or media type, and currently defined
status codes are inadequate, a new status code can be registered.
</t>
<t>
HTTP status codes are generic; that is, they are potentially applicable to
any resource, not just one particular media type, "type" of resource, or
application. As such, it is preferred that new HTTP status codes be
registered in a document that isn't specific to a single application, so
that this is clear.
</t>
<t>
Definitions of new HTTP status codes typically explain the request
conditions that produce a response containing the status code (e.g.,
combinations of request headers and/or method(s)), along with any
interactions with response headers (e.g., those that are required, those
that modify the semantics of the response).
</t>
<t>
New HTTP status codes are required to fall under one of the categories
defined in <xref target="status.codes"/>. To allow existing parsers to
properly handle them, new status codes cannot disallow a response body,
although they can mandate a zero-length response body. They can require the
presence of one or more particular HTTP response header(s).
</t>
<t>
Likewise, their definitions can specify that caches are allowed to use
heuristics to determine their freshness (see <xref target="Part6"/>; by default, it is
not allowed), and can define how to determine the resource which they
carry a representation for (see <xref target="identifying.response.associated.with.representation"/>; by default,
it is anonymous).
</t>
</section>
</section>
</section>
<section title="Response Header Fields" anchor="response.header.fields">
<t>
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 <xref target="Part1"/>).
</t>
<texttable align="left">
<ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
<c>Accept-Ranges</c> <c>Section 5.1 of <xref target="Part5"/></c>
<c>Age</c> <c>Section 3.1 of <xref target="Part6"/></c>
<c>Allow</c> <c><xref target="header.allow"/></c>
<c>ETag</c> <c>Section 6.1 of <xref target="Part4"/></c>
<c>Location</c> <c><xref target="header.location"/></c>
<c>Proxy-Authenticate</c> <c>Section 4.2 of <xref target="Part7"/></c>
<c>Retry-After</c> <c><xref target="header.retry-after"/></c>
<c>Server</c> <c><xref target="header.server"/></c>
<c>Vary</c> <c>Section 3.5 of <xref target="Part6"/></c>
<c>WWW-Authenticate</c> <c>Section 4.4 of <xref target="Part7"/></c>
</texttable>
</section>
<section title="Representation" anchor="representation">
<t>
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 <xref target="Part3"/>.
</t>
<t>
A representation body is only present in a message when a message-body is
present, as described in Section 3.3 of <xref target="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.
</t>
<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
<t>
It is sometimes necessary to determine an identifier for the resource
associated with a representation.
</t>
<t>
An HTTP request representation, when present, is always associated with an
anonymous (i.e., unidentified) resource.
</t>
<t>
In the common case, an HTTP response is a representation of the target
resource (see Section 4.3 of <xref target="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):
</t>
<t><list style="numbers">
<t>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.</t>
<t>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
resource (see Section 2.8 of <xref target="Part6"/>).</t>
<t>If the response has a Content-Location header field, and that URI is the same
as the effective request URI, the response payload is a representation of the
target resource.</t>
<t>If the response has a Content-Location header field, 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).</t>
<t>Otherwise, the response is a representation of an anonymous (i.e.,
unidentified) resource.</t>
</list></t>
<t>
<cref anchor="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.</cref>
</t>
</section>
</section>
<section title="Method Definitions" anchor="method.definitions">
<t>
The set of common request 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.
</t>
<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
<section title="Safe Methods" anchor="safe.methods">
<iref item="Safe Methods" primary="true"/>
<t>
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.
</t>
<t>
In particular, the convention has been established that the GET, HEAD,
OPTIONS, and TRACE request methods SHOULD NOT have the significance
of taking an action other than retrieval. These request 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.
</t>
<t>
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.
</t>
</section>
<section title="Idempotent Methods" anchor="idempotent.methods">
<iref item="Idempotent Methods" primary="true"/>
<t>
Request 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.
PUT, DELETE, and all safe request 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.
</t>
</section>
</section>
<section title="OPTIONS" anchor="OPTIONS">
<iref primary="true" item="OPTIONS method"/>
<iref primary="true" item="Methods" subitem="OPTIONS"/>
<t>
The OPTIONS method requests information about the
communication options available on the request/response chain
identified by the effective request URI. This method allows a 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.
</t>
<t>
Responses to the OPTIONS method are not cacheable.
</t>
<t>
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.
</t>
<t>
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).
</t>
<t>
If the request-target is not an asterisk, the OPTIONS request applies
only to the options that are available when communicating with that
resource.
</t>
<t>
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".
</t>
<t>
The Max-Forwards header field MAY be used to target a
specific proxy in the request chain (see <xref target="header.max-forwards"/>).
If no Max-Forwards field is present in the request, then the forwarded
request MUST NOT include a Max-Forwards field.
</t>
</section>
<section title="GET" anchor="GET">
<iref primary="true" item="GET method"/>
<iref primary="true" item="Methods" subitem="GET"/>
<t>
The GET method requests transfer of a current representation of
the target resource.
</t>
<t>
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.
</t>
<t>
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
requests that the representation be transferred only under the
circumstances described by the conditional header field(s). The
conditional GET request 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.
</t>
<t>
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 <xref target="Part5"/>.
The partial GET request is intended to reduce unnecessary
network usage by allowing partially-retrieved representations to be
completed without transferring data already held by the client.
</t>
<t>
The response to a GET request is cacheable and MAY be used to satisfy
subsequent GET and HEAD requests (see <xref target="Part6"/>).
</t>
<t>
See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
</t>
</section>
<section title="HEAD" anchor="HEAD">
<iref primary="true" item="HEAD method"/>
<iref primary="true" item="Methods" subitem="HEAD"/>
<t>
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 header fields 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.
</t>
<t>
The response to a HEAD request is cacheable and MAY be used to satisfy
a subsequent HEAD request; see <xref target="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 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.
</t>
</section>
<section title="POST" anchor="POST">
<iref primary="true" item="POST method"/>
<iref primary="true" item="Methods" subitem="POST"/>
<t>
The POST method requests 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:
<list style="symbols">
<t>
Annotation of existing resources;
</t>
<t>
Posting a message to a bulletin board, newsgroup, mailing list,
or similar group of articles;
</t>
<t>
Providing a block of data, such as the result of submitting a
form, to a data-handling process;
</t>
<t>
Extending a database through an append operation.
</t>
</list>
</t>
<t>
The actual function performed by the POST method is determined by the
server and is usually dependent on the effective request URI.
</t>
<t>
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.
</t>
<t>
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 field (see <xref target="header.location"/>).
</t>
<t>
Responses to POST requests are only cacheable when they
include explicit freshness information (see Section 2.3.1 of <xref target="Part6"/>). A
cached POST response with a Content-Location header field
(see Section 6.7 of <xref target="Part3"/>) whose value is the effective
Request URI MAY be used to satisfy subsequent GET and HEAD requests.
</t>
<t>
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.
</t>
</section>
<section title="PUT" anchor="PUT">
<iref primary="true" item="PUT method"/>
<iref primary="true" item="Methods" subitem="PUT"/>
<t>
The PUT method requests that the state of the target resource
be created or replaced with the state defined by the representation
enclosed in the request message payload. A successful PUT of a given
representation would suggest that a subsequent GET on that same target
resource will result in an equivalent representation being returned in
a 200 (OK) response. However, there is no guarantee that such a state
change will be observable, since the target resource might be acted
upon by other user agents in parallel, or might be subject to dynamic
processing by the origin server, before any subsequent GET is received.
A successful response only implies that the user agent's intent was
achieved at the time of its processing by the origin server.
</t>
<t>
If the target resource does not have a current representation and
the PUT successfully creates one, then the origin server MUST inform
the user agent by sending a 201 (Created) response. If the target
resource does have a current representation and that representation is
successfully modified in accordance with the state of the enclosed
representation, then either a 200 (OK) or 204 (No Content) response
SHOULD be sent to indicate successful completion of the request.
</t>
<t>
Unrecognized header fields SHOULD be ignored (i.e., not saved
as part of the resource state).
</t>
<t>
An origin server SHOULD verify that the PUT representation is
consistent with any constraints which the server has for the target
resource that cannot or will not be changed by the PUT. This is
particularly important when the origin server uses internal
configuration information related to the URI in order to set the
values for representation metadata on GET responses. When a PUT
representation is inconsistent with the target resource, the origin
server SHOULD either make them consistent, by transforming the
representation or changing the resource configuration, or respond
with an appropriate error message containing sufficient information
to explain why the representation is unsuitable. The 409 (Conflict)
or 415 (Unsupported Media Type) status codes are suggested, with the
latter being specific to constraints on Content-Type values.
</t>
<t>
For example, if the target resource is configured to always have a
Content-Type of "text/html" and the representation being PUT has a
Content-Type of "image/jpeg", then the origin server SHOULD do one of:
(a) reconfigure the target resource to reflect the new media type;
(b) transform the PUT representation to a format consistent with that
of the resource before saving it as the new resource state; or,
(c) reject the request with a 415 response indicating that the target
resource is limited to "text/html", perhaps including a link to a
different resource that would be a suitable target for the new
representation.
</t>
<t>
HTTP does not define exactly how a PUT method affects the state
of an origin server beyond what can be expressed by the intent of
the user agent request and the semantics of the origin server response.
It does not define what a resource might be, in any sense of that
word, beyond the interface provided via HTTP. It does not define
how resource state is "stored", nor how such storage might change
as a result of a change in resource state, nor how the origin server
translates resource state into representations. Generally speaking,
all implementation details behind the resource interface are
intentionally hidden by the server.
</t>
<t>
The fundamental difference between the POST and PUT methods is
highlighted by the different intent for the target resource.
The target resource in a POST request is intended to handle the
enclosed representation as a data-accepting process, such as for
a gateway to some other protocol or a document that accepts annotations.
In contrast, the target resource in a PUT request is intended to
take the enclosed representation as a new or replacement value.
Hence, the intent of PUT is idempotent and visible to intermediaries,
even though the exact effect is only known by the origin server.
</t>
<t>
Proper interpretation of a PUT request presumes that the user agent
knows what target resource is desired. A service that is intended
to select a proper URI on behalf of the client, after receiving
a state-changing request, SHOULD be implemented using the POST
method rather than PUT. If the origin server will not make the
requested PUT state change to the target resource and instead
wishes to have it applied to a different resource, such as when the
resource has been moved to a different URI, then the origin server
MUST send a 301 (Moved Permanently) response; the user agent MAY
then make its own decision regarding whether or not to redirect the
request.
</t>
<t>
A PUT request applied to the target resource MAY have side-effects
on other resources. For example, an article might have a URI for
identifying "the current version" (a resource) which is separate
from the URIs identifying each particular version (different
resources that at one point shared the same state as the current version
resource). A successful PUT request on "the current version" URI might
therefore create a new version resource in addition to changing the
state of the target resource, and might also cause links to be added
between the related resources.
</t>
<t>
An origin server SHOULD reject any PUT request that contains a
Content-Range header field, since it might be misinterpreted as
partial content (or might be partial content that is being mistakenly
PUT as a full representation). Partial content updates are
possible by targeting a separately identified resource with state
that overlaps a portion of the larger resource, or by using a
different method that has been specifically defined for partial
updates (for example, the PATCH method defined in
<xref target="RFC5789"/>).
</t>
<t>
Responses to the PUT method are not cacheable. If a PUT request passes
through a cache that has one or more stored responses for the effective
request URI, those stored responses will be invalidated (see
Section 2.5 of <xref target="Part6"/>).
</t>
</section>
<section title="DELETE" anchor="DELETE">
<iref primary="true" item="DELETE method"/>
<iref primary="true" item="Methods" subitem="DELETE"/>
<t>
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.
</t>
<t>
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.
</t>
<t>
Responses to the DELETE method are not cacheable. If a DELETE request
passes through a cache that has one or more stored responses for the
effective request URI, those stored responses will be invalidated (see
Section 2.5 of <xref target="Part6"/>).
</t>
</section>
<section title="TRACE" anchor="TRACE">
<iref primary="true" item="TRACE method"/>
<iref primary="true" item="Methods" subitem="TRACE"/>
<t>
The TRACE method requests 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 to receive a Max-Forwards
value of zero (0) in the request (see <xref target="header.max-forwards"/>).
A TRACE request MUST NOT include a message-body.
</t>
<t>
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 <xref target="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.
</t>
<t>
If the request is valid, the response SHOULD have a Content-Type of
"message/http" (see Section 10.3.1 of <xref target="Part1"/>) and contain a message-body
that encloses a copy of the entire request message.
Responses to the TRACE method are not cacheable.
</t>
</section>
<section title="CONNECT" anchor="CONNECT">
<iref primary="true" item="CONNECT method"/>
<iref primary="true" item="Methods" subitem="CONNECT"/>
<t>
The CONNECT method requests that the proxy establish a tunnel
to the request-target and then restrict its behavior to blind
forwarding of packets until the connection is closed.
</t>
<t>
When using CONNECT, the request-target MUST use the authority form
(Section 4.1.2 of <xref target="Part1"/>); i.e., the request-target consists of only the
host name and port number of the tunnel destination, separated by a colon.
For example,
</t>
<figure><artwork type="message/http; msgtype="request""><![CDATA[
CONNECT server.example.com:80 HTTP/1.1
Host: server.example.com:80
]]></artwork></figure>
<t>
Other HTTP mechanisms can be used normally with the CONNECT method —
except end-to-end protocol Upgrade requests, since the
tunnel must be established first.
</t>
<t>
For example, proxy authentication might be used to establish the
authority to create a tunnel:
</t>
<figure><artwork type="message/http; msgtype="request""><![CDATA[
CONNECT server.example.com:80 HTTP/1.1
Host: server.example.com:80
Proxy-Authorization: basic aGVsbG86d29ybGQ=
]]></artwork></figure>
<t>
Like any other pipelined HTTP/1.1 request, data to be tunnel may be
sent immediately after the blank line. The usual caveats also apply:
data may be discarded if the eventual response is negative, and the
connection may be reset with no response if more than one TCP segment
is outstanding.
</t>
<section title="Establishing a Tunnel with CONNECT">
<t>
Any successful (2xx) response to a CONNECT request indicates that the
proxy has established a connection to the requested host and port,
and has switched to tunneling the current connection to that server
connection.
</t>
<t>
It may be the case that the proxy itself can only reach the requested
origin server through another proxy. In this case, the first proxy
SHOULD make a CONNECT request of that next proxy, requesting a tunnel
to the authority. A proxy MUST NOT respond with any 2xx status code
unless it has either a direct or tunnel connection established to the
authority.
</t>
<t>
An origin server which receives a CONNECT request for itself MAY
respond with a 2xx status code to indicate that a connection is
established.
</t>
<t>
If at any point either one of the peers gets disconnected, any
outstanding data that came from that peer will be passed to the other
one, and after that also the other connection will be terminated by
the proxy. If there is outstanding data to that peer undelivered,
that data will be discarded.
</t>
</section>
</section>
</section>
<section title="Status Code Definitions" anchor="status.codes">
<t>
Each Status-Code is described below, including any metadata required
in the response.
</t>
<section title="Informational 1xx" anchor="status.1xx">
<t>
This class of status code indicates a provisional response,
consisting only of the Status-Line and optional header fields, and is
terminated by an empty line. There are no required header fields 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.
</t>
<t>
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.
</t>
<t>
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).)
</t>
<section title="100 Continue" anchor="status.100">
<iref primary="true" item="100 Continue (status code)"/>
<iref primary="true" item="Status Codes" subitem="100 Continue"/>
<t>
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 <xref target="Part1"/> for detailed discussion of the use and handling of this
status code.
</t>
</section>
<section title="101 Switching Protocols" anchor="status.101">
<iref primary="true" item="101 Switching Protocols (status code)"/>
<iref primary="true" item="Status Codes" subitem="101 Switching Protocols"/>
<t>
The server understands and is willing to comply with the client's
request, via the Upgrade message header field (Section 9.8 of <xref target="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.
</t>
<t>
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.
</t>
</section>
</section>
<section title="Successful 2xx" anchor="status.2xx">
<t>
This class of status code indicates that the client's request was
successfully received, understood, and accepted.
</t>
<section title="200 OK" anchor="status.200">
<iref primary="true" item="200 OK (status code)"/>
<iref primary="true" item="Status Codes" subitem="200 OK"/>
<t>
The request has succeeded. The payload returned with the response
is dependent on the method used in the request, for example:
<list style="hanging">
<t hangText="GET">
a representation of the target resource is sent in the response;
</t>
<t hangText="HEAD">
the same representation as GET, except without the message-body;
</t>
<t hangText="POST">
a representation describing or containing the result of the action;
</t>
<t hangText="TRACE">
a representation containing the request message as received by the
end server.
</t>
</list>
</t>
<t>
Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
freshness for 200 responses.
</t>
</section>
<section title="201 Created" anchor="status.201">
<iref primary="true" item="201 Created (status code)"/>
<iref primary="true" item="Status Codes" subitem="201 Created"/>
<t>
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
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.
</t>
<t>
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 <xref target="Part4"/>).
</t>
</section>
<section title="202 Accepted" anchor="status.202">
<iref primary="true" item="202 Accepted (status code)"/>
<iref primary="true" item="Status Codes" subitem="202 Accepted"/>
<t>
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.
</t>
<t>
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.
</t>
</section>
<section title="203 Non-Authoritative Information" anchor="status.203">
<iref primary="true" item="203 Non-Authoritative Information (status code)"/>
<iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information"/>
<t>
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).
</t>
<t>
Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
freshness for 203 responses.
</t>
</section>
<section title="204 No Content" anchor="status.204">
<iref primary="true" item="204 No Content (status code)"/>
<iref primary="true" item="Status Codes" subitem="204 No Content"/>
<t>
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 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.
</t>
<t>
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.
</t>
<t>
The 204 response MUST NOT include a message-body, and thus is always
terminated by the first empty line after the header fields.
</t>
</section>
<section title="205 Reset Content" anchor="status.205">
<iref primary="true" item="205 Reset Content (status code)"/>
<iref primary="true" item="Status Codes" subitem="205 Reset Content"/>
<t>
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.
</t>
<t>
The message-body included with the response MUST be empty. Note that
receivers still need to parse the response according to the algorithm defined
in Section 3.3 of <xref target="Part1"/>.
</t>
</section>
<section title="206 Partial Content" anchor="status.206">
<iref primary="true" item="206 Partial Content (status code)"/>
<iref primary="true" item="Status Codes" subitem="206 Partial Content"/>
<t>
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 <xref target="Part5"/>.
</t>
<t>
Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
freshness for 206 responses.
</t>
</section>
</section>
<section title="Redirection 3xx" anchor="status.3xx">
<t>
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 <xref target="safe.methods"/>.
A client SHOULD detect infinite redirection loops, since such loops
generate network traffic for each redirection.
</t>
<t><list>
<t>
Note: An earlier version of this specification recommended a
maximum of five redirections (<xref target="RFC2068"/>, Section 10.3).
Content developers need to be aware that some clients might
implement such a fixed limitation.
</t>
</list></t>
<section title="300 Multiple Choices" anchor="status.300">
<iref primary="true" item="300 Multiple Choices (status code)"/>
<iref primary="true" item="Status Codes" subitem="300 Multiple Choices"/>
<t>
The target resource has more than one
representation, each with its own specific location, and agent-driven
negotiation information (Section 5 of <xref target="Part3"/>) is being provided so that
the user (or user agent) can select a preferred representation by
redirecting its request to that location.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
freshness for 300 responses.
</t>
</section>
<section title="301 Moved Permanently" anchor="status.301">
<iref primary="true" item="301 Moved Permanently (status code)"/>
<iref primary="true" item="Status Codes" subitem="301 Moved Permanently"/>
<t>
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.
</t>
<t>
Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
freshness for 301 responses.
</t>
<t>
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).
</t>
<t>
If the 301 status code is received in response to a request method
that is known to be "safe", as defined in <xref target="safe.methods"/>,
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.
</t>
<t><list>
<t>
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.
</t>
</list></t>
</section>
<section title="302 Found" anchor="status.302">
<iref primary="true" item="302 Found (status code)"/>
<iref primary="true" item="Status Codes" subitem="302 Found"/>
<t>
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.
</t>
<t>
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).
</t>
<t>
If the 302 status code is received in response to a request method
that is known to be "safe", as defined in <xref target="safe.methods"/>,
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.
</t>
<t><list>
<t>
Note: HTTP/1.0 (<xref target="RFC1945"/>, Section 9.3)
and the first version of HTTP/1.1 (<xref target="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
(<xref target="RFC2616"/>, Section 10.3.3) has added the
status codes
<xref target="status.303" format="none">303</xref> and
<xref target="status.307" format="none">307</xref> for servers that wish
to make unambiguously clear which kind of reaction is expected of the
client.
</t>
</list></t>
</section>
<section title="303 See Other" anchor="status.303">
<iref primary="true" item="303 See Other (status code)"/>
<iref primary="true" item="Status Codes" subitem="303 See Other"/>
<t>
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.
</t>
<t>
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 original request.
</t>
<t>
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).
</t>
<t>
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.
</t>
</section>
<section title="304 Not Modified" anchor="status.304">
<iref primary="true" item="304 Not Modified (status code)"/>
<iref primary="true" item="Status Codes" subitem="304 Not Modified"/>
<t>
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 <xref target="Part4"/>.
</t>
</section>
<section title="305 Use Proxy" anchor="status.305">
<iref primary="true" item="305 Use Proxy (status code)"/>
<iref primary="true" item="Status Codes" subitem="305 Use Proxy"/>
<t>
The 305 status code was defined in a previous version of this specification
(see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
</t>
</section>
<section title="306 (Unused)" anchor="status.306">
<iref primary="true" item="306 (Unused) (status code)"/>
<iref primary="true" item="Status Codes" subitem="306 (Unused)"/>
<t>
The 306 status code was used in a previous version of the
specification, is no longer used, and the code is reserved.
</t>
</section>
<section title="307 Temporary Redirect" anchor="status.307">
<iref primary="true" item="307 Temporary Redirect (status code)"/>
<iref primary="true" item="Status Codes" subitem="307 Temporary Redirect"/>
<t>
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.
</t>
<t>
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.
</t>
<t>
If the 307 status code is received in response to a request method
that is known to be "safe", as defined in <xref target="safe.methods"/>,
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.
</t>
</section>
</section>
<section title="Client Error 4xx" anchor="status.4xx">
<t>
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.
</t>
<t>
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.
</t>
<section title="400 Bad Request" anchor="status.400">
<iref primary="true" item="400 Bad Request (status code)"/>
<iref primary="true" item="Status Codes" subitem="400 Bad Request"/>
<t>
The request could not be understood by the server due to malformed
syntax. The client SHOULD NOT repeat the request without
modifications.
</t>
</section>
<section title="401 Unauthorized" anchor="status.401">
<iref primary="true" item="401 Unauthorized (status code)"/>
<iref primary="true" item="Status Codes" subitem="401 Unauthorized"/>
<t>
The request requires user authentication (see Section 3.1 of <xref target="Part7"/>).
</t>
</section>
<section title="402 Payment Required" anchor="status.402">
<iref primary="true" item="402 Payment Required (status code)"/>
<iref primary="true" item="Status Codes" subitem="402 Payment Required"/>
<t>
This code is reserved for future use.
</t>
</section>
<section title="403 Forbidden" anchor="status.403">
<iref primary="true" item="403 Forbidden (status code)"/>
<iref primary="true" item="Status Codes" subitem="403 Forbidden"/>
<t>
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.
</t>
</section>
<section title="404 Not Found" anchor="status.404">
<iref primary="true" item="404 Not Found (status code)"/>
<iref primary="true" item="Status Codes" subitem="404 Not Found"/>
<t>
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.
</t>
</section>
<section title="405 Method Not Allowed" anchor="status.405">
<iref primary="true" item="405 Method Not Allowed (status code)"/>
<iref primary="true" item="Status Codes" subitem="405 Method Not Allowed"/>
<t>
The method specified in the Request-Line is not allowed for the target
resource. The response MUST include an
Allow header field containing a list of valid methods for the requested
resource.
</t>
</section>
<section title="406 Not Acceptable" anchor="status.406">
<iref primary="true" item="406 Not Acceptable (status code)"/>
<iref primary="true" item="Status Codes" subitem="406 Not Acceptable"/>
<t>
The resource identified by the request is only capable of generating
response representations which have content characteristics not acceptable
according to the accept header fields sent in the request.
</t>
<t>
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.
</t>
<t><list>
<t>
Note: HTTP/1.1 servers are allowed to return responses which are
not acceptable according to the accept header fields sent in the
request. In some cases, this might even be preferable to sending a
406 response. User agents are encouraged to inspect the header fields of
an incoming response to determine if it is acceptable.
</t>
</list></t>
<t>
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.
</t>
</section>
<section title="407 Proxy Authentication Required" anchor="status.407">
<iref primary="true" item="407 Proxy Authentication Required (status code)"/>
<iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required"/>
<t>
This code is similar to 401 (Unauthorized), but indicates that the
client must first authenticate itself with the proxy (see Section 3.2 of <xref target="Part7"/>).
</t>
</section>
<section title="408 Request Timeout" anchor="status.408">
<iref primary="true" item="408 Request Timeout (status code)"/>
<iref primary="true" item="Status Codes" subitem="408 Request Timeout"/>
<t>
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.
</t>
</section>
<section title="409 Conflict" anchor="status.409">
<iref primary="true" item="409 Conflict (status code)"/>
<iref primary="true" item="Status Codes" subitem="409 Conflict"/>
<t>
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.
</t>
<t>
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.
</t>
</section>
<section title="410 Gone" anchor="status.410">
<iref primary="true" item="410 Gone (status code)"/>
<iref primary="true" item="Status Codes" subitem="410 Gone"/>
<t>
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.
</t>
<t>
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.
</t>
<t>
Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine freshness
for 410 responses.
</t>
</section>
<section title="411 Length Required" anchor="status.411">
<iref primary="true" item="411 Length Required (status code)"/>
<iref primary="true" item="Status Codes" subitem="411 Length Required"/>
<t>
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.
</t>
</section>
<section title="412 Precondition Failed" anchor="status.412">
<iref primary="true" item="412 Precondition Failed (status code)"/>
<iref primary="true" item="Status Codes" subitem="412 Precondition Failed"/>
<t>
The precondition given in one or more of the header fields
evaluated to false when it was tested on the server, as defined in
Section 3.2 of <xref target="Part4"/>.
</t>
</section>
<section title="413 Request Entity Too Large" anchor="status.413">
<iref primary="true" item="413 Request Entity Too Large (status code)"/>
<iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large"/>
<t>
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.
</t>
<t>
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.
</t>
</section>
<section title="414 URI Too Long" anchor="status.414">
<iref primary="true" item="414 URI Too Long (status code)"/>
<iref primary="true" item="Status Codes" subitem="414 URI Too Long"/>
<t>
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.
</t>
</section>
<section title="415 Unsupported Media Type" anchor="status.415">
<iref primary="true" item="415 Unsupported Media Type (status code)"/>
<iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type"/>
<t>
The server is refusing to service the request because the request
payload is in a format not supported by this request method on the
target resource.
</t>
</section>
<section title="416 Requested Range Not Satisfiable" anchor="status.416">
<iref primary="true" item="416 Requested Range Not Satisfiable (status code)"/>
<iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable"/>
<t>
The request included a Range header field (Section 5.4 of <xref target="Part5"/>) and none of
the range-specifier values in this field overlap the current extent
of the selected resource. See Section 3.2 of <xref target="Part5"/>.
</t>
</section>
<section title="417 Expectation Failed" anchor="status.417">
<iref primary="true" item="417 Expectation Failed (status code)"/>
<iref primary="true" item="Status Codes" subitem="417 Expectation Failed"/>
<t>
The expectation given in an Expect header field (see <xref target="header.expect"/>)
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.
</t>
</section>
<section title="426 Upgrade Required" anchor="status.426">
<iref primary="true" item="426 Upgrade Required (status code)"/>
<iref primary="true" item="Status Codes" subitem="426 Upgrade Required"/>
<t>
The request can not be completed without a prior protocol upgrade. This
response MUST include an Upgrade header field (Section 9.8 of <xref target="Part1"/>)
specifying the required protocols.
</t>
<figure>
<preamble>Example:</preamble>
<artwork type="message/http; msgtype="request""><![CDATA[
HTTP/1.1 426 Upgrade Required
Upgrade: HTTP/2.0
Connection: Upgrade
]]></artwork></figure>
<t>
The server SHOULD include a message body in the 426 response which
indicates in human readable form the reason for the error and describes any
alternative courses which may be available to the user.
</t>
</section>
</section>
<section title="Server Error 5xx" anchor="status.5xx">
<t>
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.
</t>
<section title="500 Internal Server Error" anchor="status.500">
<iref primary="true" item="500 Internal Server Error (status code)"/>
<iref primary="true" item="Status Codes" subitem="500 Internal Server Error"/>
<t>
The server encountered an unexpected condition which prevented it
from fulfilling the request.
</t>
</section>
<section title="501 Not Implemented" anchor="status.501">
<iref primary="true" item="501 Not Implemented (status code)"/>
<iref primary="true" item="Status Codes" subitem="501 Not Implemented"/>
<t>
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.
</t>
</section>
<section title="502 Bad Gateway" anchor="status.502">
<iref primary="true" item="502 Bad Gateway (status code)"/>
<iref primary="true" item="Status Codes" subitem="502 Bad Gateway"/>
<t>
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.
</t>
</section>
<section title="503 Service Unavailable" anchor="status.503">
<iref primary="true" item="503 Service Unavailable (status code)"/>
<iref primary="true" item="Status Codes" subitem="503 Service Unavailable"/>
<t>
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 field. If no Retry-After is given, the client SHOULD
handle the response as it would for a 500 response.
</t>
<t><list>
<t>
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.
</t>
</list></t>
</section>
<section title="504 Gateway Timeout" anchor="status.504">
<iref primary="true" item="504 Gateway Timeout (status code)"/>
<iref primary="true" item="Status Codes" subitem="504 Gateway Timeout"/>
<t>
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.
</t>
<t><list>
<t>
Note to implementors: some deployed proxies are known to
return 400 or 500 when DNS lookups time out.
</t>
</list></t>
</section>
<section title="505 HTTP Version Not Supported" anchor="status.505">
<iref primary="true" item="505 HTTP Version Not Supported (status code)"/>
<iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported"/>
<t>
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 <xref target="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.
</t>
</section>
</section>
</section>
<section title="Header Field Definitions" anchor="header.fields">
<t>
This section defines the syntax and semantics of HTTP/1.1 header fields
related to request and response semantics.
</t>
<section title="Allow" anchor="header.allow">
<iref primary="true" item="Allow header field"/>
<iref primary="true" item="Header Fields" subitem="Allow"/>
<t>
The "Allow" 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 request methods associated with the resource.
</t>
<figure><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/><artwork type="abnf2616"><![CDATA[
Allow = "Allow" ":" OWS Allow-v
Allow-v = #Method
]]></artwork></figure>
<t>
Example of use:
</t>
<figure><artwork type="example"><![CDATA[
Allow: GET, HEAD, PUT
]]></artwork></figure>
<t>
The actual set of allowed methods is defined by the origin server at the
time of each request.
</t>
<t>
A proxy MUST NOT modify the Allow header field — it does not need to
understand all the methods specified in order to handle them according to
the generic message handling rules.
</t>
</section>
<section title="Expect" anchor="header.expect">
<iref primary="true" item="Expect header field"/>
<iref primary="true" item="Header Fields" subitem="Expect"/>
<t>
The "Expect" header field is used to indicate that particular
server behaviors are required by the client.
</t>
<figure><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/><artwork type="abnf2616"><![CDATA[
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 ) ]
]]></artwork></figure>
<t>
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.
</t>
<t>
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.
</t>
<t>
Comparison of expectation values is case-insensitive for unquoted
tokens (including the 100-continue token), and is case-sensitive for
quoted-string expectation-extensions.
</t>
<t>
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
header field itself is end-to-end; it MUST be forwarded if the
request is forwarded.
</t>
<t>
Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
Expect header field.
</t>
<t>
See Section 7.2.3 of <xref target="Part1"/> for the use of the 100 (Continue) status code.
</t>
</section>
<section title="From" anchor="header.from">
<iref primary="true" item="From header field"/>
<iref primary="true" item="Header Fields" subitem="From"/>
<t>
The "From" 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 <xref target="RFC5322"/>:
</t>
<figure><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/><artwork type="abnf2616"><![CDATA[
From = "From" ":" OWS From-v
From-v = mailbox
mailbox = <mailbox, defined in [RFC5322], Section 3.4>
]]></artwork></figure>
<t>
An example is:
</t>
<figure><artwork type="example"><![CDATA[
From: webmaster@example.org
]]></artwork></figure>
<t>
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 field so that the
person responsible for running the robot can be contacted if problems
occur on the receiving end.
</t>
<t>
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.
</t>
<t>
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.
</t>
</section>
<section title="Location" anchor="header.location">
<iref primary="true" item="Location header field"/>
<iref primary="true" item="Header Fields" subitem="Location"/>
<t>
The "Location" header field is used to identify a newly created
resource, or to redirect the recipient to a different location for
completion of the request.
</t>
<t>
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.
</t>
<t>
The field value consists of a single URI-reference. When it has the form
of a relative reference (<xref target="RFC3986"/>, Section 4.2),
the final value is computed by resolving it against the effective request
URI (<xref target="RFC3986"/>, Section 5).
</t>
<figure><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/><artwork type="abnf2616"><![CDATA[
Location = "Location" ":" OWS Location-v
Location-v = URI-reference
]]></artwork></figure>
<figure>
<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
<artwork type="example"><![CDATA[
Location: http://www.example.org/pub/WWW/People.html#tim
]]></artwork></figure><figure><artwork type="example"><![CDATA[ Location: /index.html
]]></artwork></figure>
<t>
There are circumstances in which a fragment identifier in a Location URI
would not be appropriate:
<list style="symbols">
<t>With a 201 Created response, because in this usage the Location header
field specifies the URI for the entire created resource.</t>
<t>With 305 Use Proxy.</t>
</list>
</t>
<t><list>
<t>
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. Thus be aware that including fragment identifiers might
inconvenience anyone relying on the semantics of the original URI's
fragment identifier.
</t>
</list></t>
<t><list>
<t>
Note: The Content-Location header field (Section 6.7 of <xref target="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.
</t>
</list></t>
</section>
<section title="Max-Forwards" anchor="header.max-forwards">
<iref primary="true" item="Max-Forwards header field"/>
<iref primary="true" item="Header Fields" subitem="Max-Forwards"/>
<t>
The "Max-Forwards" header field provides a mechanism with the
TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
methods to limit the number of times that the request is forwarded by
proxies. This can be useful when the client is attempting to
trace a request which appears to be failing or looping in mid-chain.
</t>
<figure><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/><artwork type="abnf2616"><![CDATA[
Max-Forwards = "Max-Forwards" ":" OWS Max-Forwards-v
Max-Forwards-v = 1*DIGIT
]]></artwork></figure>
<t>
The Max-Forwards value is a decimal integer indicating the remaining
number of times this request message can be forwarded.
</t>
<t>
Each 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).
</t>
<t>
The Max-Forwards header field MAY be ignored for all other request
methods.
</t>
</section>
<section title="Referer" anchor="header.referer">
<iref primary="true" item="Referer header field"/>
<iref primary="true" item="Header Fields" subitem="Referer"/>
<t>
The "Referer" [sic] 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.).
</t>
<t>
The Referer header field 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.
</t>
<t>
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).
</t>
<figure><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/><artwork type="abnf2616"><![CDATA[
Referer = "Referer" ":" OWS Referer-v
Referer-v = absolute-URI / partial-URI
]]></artwork></figure>
<t>
Example:
</t>
<figure><artwork type="example"><![CDATA[
Referer: http://www.example.org/hypertext/Overview.html
]]></artwork></figure>
<t>
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
<xref target="encoding.sensitive.information.in.uris"/> for security considerations.
</t>
</section>
<section title="Retry-After" anchor="header.retry-after">
<iref primary="true" item="Retry-After header field"/>
<iref primary="true" item="Header Fields" subitem="Retry-After"/>
<t>
The 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.
</t>
<t>
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.
</t>
<figure><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/><artwork type="abnf2616"><![CDATA[
Retry-After = "Retry-After" ":" OWS Retry-After-v
Retry-After-v = HTTP-date / delta-seconds
]]></artwork></figure>
<t anchor="rule.delta-seconds">
Time spans are non-negative decimal integers, representing time in
seconds.
</t>
<figure><iref primary="true" item="Grammar" subitem="delta-seconds"/><artwork type="abnf2616"><![CDATA[
delta-seconds = 1*DIGIT
]]></artwork></figure>
<t>
Two examples of its use are
</t>
<figure><artwork type="example"><![CDATA[
Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
Retry-After: 120
]]></artwork></figure>
<t>
In the latter example, the delay is 2 minutes.
</t>
</section>
<section title="Server" anchor="header.server">
<iref primary="true" item="Server header field"/>
<iref primary="true" item="Header Fields" subitem="Server"/>
<t>
The "Server" header field contains information about the
software used by the origin server to handle the request.
</t>
<t>
The field can contain multiple product tokens (Section 6.3 of <xref target="Part1"/>) and
comments (Section 3.2 of <xref target="Part1"/>) identifying the server and any significant
subproducts. The product tokens are listed in order of their significance
for identifying the application.
</t>
<figure><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/><artwork type="abnf2616"><![CDATA[
Server = "Server" ":" OWS Server-v
Server-v = product
*( RWS ( product / comment ) )
]]></artwork></figure>
<t>
Example:
</t>
<figure><artwork type="example"><![CDATA[
Server: CERN/3.0 libwww/2.17
]]></artwork></figure>
<t>
If the response is being forwarded through a proxy, the proxy
application MUST NOT modify the Server header field. Instead, it
MUST include a Via field (as described in Section 9.9 of <xref target="Part1"/>).
</t>
<t><list>
<t>
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.
</t>
</list></t>
</section>
<section title="User-Agent" anchor="header.user-agent">
<iref primary="true" item="User-Agent header field"/>
<iref primary="true" item="Header Fields" subitem="User-Agent"/>
<t>
The "User-Agent" header field contains information about the user
agent originating the request. User agents SHOULD include this field with
requests.
</t>
<t>
Typically, it is used for statistical purposes, the tracing of protocol
violations, and tailoring responses to avoid particular user agent
limitations.
</t>
<t>
The field can contain multiple product tokens (Section 6.3 of <xref target="Part1"/>)
and comments (Section 3.2 of <xref target="Part1"/>) identifying the agent and its
significant subproducts. By convention, the product tokens are listed in
order of their significance for identifying the application.
</t>
<t>
Because this field is usually sent on every request a user agent makes,
implementations are encouraged not to include needlessly fine-grained
detail, and to limit (or even prohibit) the addition of subproducts by third
parties. Overly long and detailed User-Agent field values make requests
larger and can also be used to identify ("fingerprint") the user against
their wishes.
</t>
<t>
Likewise, implementations are encouraged not to use the product tokens of
other implementations in order to declare compatibility with them, as this
circumvents the purpose of the field. Finally, they are encouraged not to
use comments to identify products; doing so makes the field value more
difficult to parse.
</t>
<figure><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/><artwork type="abnf2616"><![CDATA[
User-Agent = "User-Agent" ":" OWS User-Agent-v
User-Agent-v = product *( RWS ( product / comment ) )
]]></artwork></figure>
<t>
Example:
</t>
<figure><artwork type="example"><![CDATA[
User-Agent: CERN-LineMode/2.15 libwww/2.17b3
]]></artwork></figure>
</section>
</section>
<section title="IANA Considerations" anchor="IANA.considerations">
<section title="Method Registry" anchor="method.registration">
<t>
The registration procedure for HTTP request methods is defined by
<xref target="method.registry"/> of this document.
</t>
<t>
The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
and be populated with the registrations below:
</t>
<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
<ttcol>Method</ttcol>
<ttcol>Safe</ttcol>
<ttcol>Reference</ttcol>
<c>CONNECT</c>
<c>no</c>
<c>
<xref target="CONNECT"/>
</c>
<c>DELETE</c>
<c>no</c>
<c>
<xref target="DELETE"/>
</c>
<c>GET</c>
<c>yes</c>
<c>
<xref target="GET"/>
</c>
<c>HEAD</c>
<c>yes</c>
<c>
<xref target="HEAD"/>
</c>
<c>OPTIONS</c>
<c>yes</c>
<c>
<xref target="OPTIONS"/>
</c>
<c>POST</c>
<c>no</c>
<c>
<xref target="POST"/>
</c>
<c>PUT</c>
<c>no</c>
<c>
<xref target="PUT"/>
</c>
<c>TRACE</c>
<c>yes</c>
<c>
<xref target="TRACE"/>
</c>
</texttable>
<!--(END)-->
</section>
<section title="Status Code Registry" anchor="status.code.registration">
<t>
The registration procedure for HTTP Status Codes — previously defined
in Section 7.1 of <xref target="RFC2817"/> — is now defined
by <xref target="status.code.registry"/> of this document.
</t>
<t>
The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
shall be updated with the registrations below:
</t>
<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
<ttcol>Value</ttcol>
<ttcol>Description</ttcol>
<ttcol>Reference</ttcol>
<c>100</c>
<c>Continue</c>
<c>
<xref target="status.100"/>
</c>
<c>101</c>
<c>Switching Protocols</c>
<c>
<xref target="status.101"/>
</c>
<c>200</c>
<c>OK</c>
<c>
<xref target="status.200"/>
</c>
<c>201</c>
<c>Created</c>
<c>
<xref target="status.201"/>
</c>
<c>202</c>
<c>Accepted</c>
<c>
<xref target="status.202"/>
</c>
<c>203</c>
<c>Non-Authoritative Information</c>
<c>
<xref target="status.203"/>
</c>
<c>204</c>
<c>No Content</c>
<c>
<xref target="status.204"/>
</c>
<c>205</c>
<c>Reset Content</c>
<c>
<xref target="status.205"/>
</c>
<c>300</c>
<c>Multiple Choices</c>
<c>
<xref target="status.300"/>
</c>
<c>301</c>
<c>Moved Permanently</c>
<c>
<xref target="status.301"/>
</c>
<c>302</c>
<c>Found</c>
<c>
<xref target="status.302"/>
</c>
<c>303</c>
<c>See Other</c>
<c>
<xref target="status.303"/>
</c>
<c>305</c>
<c>Use Proxy</c>
<c>
<xref target="status.305"/>
</c>
<c>306</c>
<c>(Unused)</c>
<c>
<xref target="status.306"/>
</c>
<c>307</c>
<c>Temporary Redirect</c>
<c>
<xref target="status.307"/>
</c>
<c>400</c>
<c>Bad Request</c>
<c>
<xref target="status.400"/>
</c>
<c>402</c>
<c>Payment Required</c>
<c>
<xref target="status.402"/>
</c>
<c>403</c>
<c>Forbidden</c>
<c>
<xref target="status.403"/>
</c>
<c>404</c>
<c>Not Found</c>
<c>
<xref target="status.404"/>
</c>
<c>405</c>
<c>Method Not Allowed</c>
<c>
<xref target="status.405"/>
</c>
<c>406</c>
<c>Not Acceptable</c>
<c>
<xref target="status.406"/>
</c>
<c>407</c>
<c>Proxy Authentication Required</c>
<c>
<xref target="status.407"/>
</c>
<c>408</c>
<c>Request Timeout</c>
<c>
<xref target="status.408"/>
</c>
<c>409</c>
<c>Conflict</c>
<c>
<xref target="status.409"/>
</c>
<c>410</c>
<c>Gone</c>
<c>
<xref target="status.410"/>
</c>
<c>411</c>
<c>Length Required</c>
<c>
<xref target="status.411"/>
</c>
<c>413</c>
<c>Request Entity Too Large</c>
<c>
<xref target="status.413"/>
</c>
<c>414</c>
<c>URI Too Long</c>
<c>
<xref target="status.414"/>
</c>
<c>415</c>
<c>Unsupported Media Type</c>
<c>
<xref target="status.415"/>
</c>
<c>417</c>
<c>Expectation Failed</c>
<c>
<xref target="status.417"/>
</c>
<c>426</c>
<c>Upgrade Required</c>
<c>
<xref target="status.426"/>
</c>
<c>500</c>
<c>Internal Server Error</c>
<c>
<xref target="status.500"/>
</c>
<c>501</c>
<c>Not Implemented</c>
<c>
<xref target="status.501"/>
</c>
<c>502</c>
<c>Bad Gateway</c>
<c>
<xref target="status.502"/>
</c>
<c>503</c>
<c>Service Unavailable</c>
<c>
<xref target="status.503"/>
</c>
<c>504</c>
<c>Gateway Timeout</c>
<c>
<xref target="status.504"/>
</c>
<c>505</c>
<c>HTTP Version Not Supported</c>
<c>
<xref target="status.505"/>
</c>
</texttable>
<!--(END)-->
</section>
<section title="Header Field Registration" anchor="header.field.registration">
<t>
The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
with the permanent registrations below (see <xref target="RFC3864"/>):
</t>
<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
<ttcol>Header Field Name</ttcol>
<ttcol>Protocol</ttcol>
<ttcol>Status</ttcol>
<ttcol>Reference</ttcol>
<c>Allow</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.allow"/>
</c>
<c>Expect</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.expect"/>
</c>
<c>From</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.from"/>
</c>
<c>Location</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.location"/>
</c>
<c>Max-Forwards</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.max-forwards"/>
</c>
<c>Referer</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.referer"/>
</c>
<c>Retry-After</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.retry-after"/>
</c>
<c>Server</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.server"/>
</c>
<c>User-Agent</c>
<c>http</c>
<c>standard</c>
<c>
<xref target="header.user-agent"/>
</c>
</texttable>
<!--(END)-->
<t>
The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
</t>
</section>
</section>
<section title="Security Considerations" anchor="security.considerations">
<t>
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.
</t>
<section title="Transfer of Sensitive Information" anchor="security.sensitive">
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
The Referer header field 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 field might indicate a private document's URI whose
publication would be inappropriate.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) 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.
</t>
<t>
Furthermore, the User-Agent header field may contain enough entropy to be
used, possibly in conjunction with other material, to uniquely identify the
user.
</t>
<t>
Some request methods, like TRACE (<xref target="TRACE"/>), expose information
that was sent in request header fields within the body of their response.
Clients SHOULD be careful with sensitive information, like Cookies,
Authorization credentials, and other header fields that might be used to
collect data from the client.
</t>
</section>
<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
<t>
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.
</t>
<t>
Clients SHOULD NOT include a Referer header field in a (non-secure)
HTTP request if the referring page was transferred with a secure
protocol.
</t>
<t>
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.
</t>
</section>
<section title="Location Headers and Spoofing" anchor="location.spoofing">
<t>
If a single server supports multiple organizations that do not trust
one another, then it MUST check the values of Location and Content-Location
header fields 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.
</t>
</section>
<section title="Security Considerations for CONNECT">
<t>
Since tunneled data is opaque to the proxy, there are additional
risks to tunneling to other well-known or reserved ports.
A HTTP client CONNECTing to port 25 could relay spam
via SMTP, for example. As such, proxies SHOULD restrict CONNECT
access to a small number of known ports.
</t>
</section>
</section>
<section title="Acknowledgments" anchor="ack">
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="Part1">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="March" year="2011"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-13"/>
</reference>
<reference anchor="Part3">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="March" year="2011"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-13"/>
</reference>
<reference anchor="Part4">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="March" year="2011"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-13"/>
</reference>
<reference anchor="Part5">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="March" year="2011"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-13"/>
</reference>
<reference anchor="Part6">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
<address><email>mnot@mnot.net</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="March" year="2011"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-13"/>
</reference>
<reference anchor="Part7">
<front>
<title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>fielding@gbiv.com</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
<address><email>jg@freedesktop.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization abbrev="HP">Hewlett-Packard Company</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>henrikn@microsoft.com</email></address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address><email>LMM@acm.org</email></address>
</author>
<author initials="P." surname="Leach" fullname="Paul J. Leach">
<organization abbrev="Microsoft">Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
<organization abbrev="W3C">World Wide Web Consortium</organization>
<address><email>ylafon@w3.org</email></address>
</author>
<author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
<organization abbrev="greenbytes">greenbytes GmbH</organization>
<address><email>julian.reschke@greenbytes.de</email></address>
</author>
<date month="March" year="2011"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-13"/>
</reference>
<reference anchor="RFC2119">
<front>
<title>Key words for use in RFCs to Indicate Requirement Levels</title>
<author initials="S." surname="Bradner" fullname="Scott Bradner">
<organization>Harvard University</organization>
<address><email>sob@harvard.edu</email></address>
</author>
<date month="March" year="1997"/>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
</reference>
<reference anchor="RFC3986">
<front>
<title abbrev="URI Generic Syntax">Uniform Resource Identifier (URI): Generic Syntax</title>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
<address>
<email>timbl@w3.org</email>
<uri>http://www.w3.org/People/Berners-Lee/</uri>
</address>
</author>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding">
<organization abbrev="Day Software">Day Software</organization>
<address>
<email>fielding@gbiv.com</email>
<uri>http://roy.gbiv.com/</uri>
</address>
</author>
<author initials="L." surname="Masinter" fullname="Larry Masinter">
<organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
<address>
<email>LMM@acm.org</email>
<uri>http://larry.masinter.net/</uri>
</address>
</author>
<date month="January" year="2005"/>
</front>
<seriesInfo name="STD" value="66"/>
<seriesInfo name="RFC" value="3986"/>
</reference>
<reference anchor="RFC5234">
<front>
<title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
<author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
<organization>Brandenburg InternetWorking</organization>
<address>
<email>dcrocker@bbiw.net</email>
</address>
</author>
<author initials="P." surname="Overell" fullname="Paul Overell">
<organization>THUS plc.</organization>
<address>
<email>paul.overell@thus.net</email>
</address>
</author>
<date month="January" year="2008"/>
</front>
<seriesInfo name="STD" value="68"/>
<seriesInfo name="RFC" value="5234"/>
</reference>
</references>
<references title="Informative References">
<reference anchor="RFC1945">
<front>
<title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization>MIT, Laboratory for Computer Science</organization>
<address><email>timbl@w3.org</email></address>
</author>
<author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
<organization>University of California, Irvine, Department of Information and Computer Science</organization>
<address><email>fielding@ics.uci.edu</email></address>
</author>
<author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
<organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
<address><email>frystyk@w3.org</email></address>
</author>
<date month="May" year="1996"/>
</front>
<seriesInfo name="RFC" value="1945"/>
</reference>
<reference anchor="RFC2068">
<front>
<title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding">
<organization>University of California, Irvine, Department of Information and Computer Science</organization>
<address><email>fielding@ics.uci.edu</email></address>
</author>
<author initials="J." surname="Gettys" fullname="Jim Gettys">
<organization>MIT Laboratory for Computer Science</organization>
<address><email>jg@w3.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
<organization>Digital Equipment Corporation, Western Research Laboratory</organization>
<address><email>mogul@wrl.dec.com</email></address>
</author>
<author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
<organization>MIT Laboratory for Computer Science</organization>
<address><email>frystyk@w3.org</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
<organization>MIT Laboratory for Computer Science</organization>
<address><email>timbl@w3.org</email></address>
</author>
<date month="January" year="1997"/>
</front>
<seriesInfo name="RFC" value="2068"/>
</reference>
<reference anchor="RFC2616">
<front>
<title>Hypertext Transfer Protocol -- HTTP/1.1</title>
<author initials="R." surname="Fielding" fullname="R. Fielding">
<organization>University of California, Irvine</organization>
<address><email>fielding@ics.uci.edu</email></address>
</author>
<author initials="J." surname="Gettys" fullname="J. Gettys">
<organization>W3C</organization>
<address><email>jg@w3.org</email></address>
</author>
<author initials="J." surname="Mogul" fullname="J. Mogul">
<organization>Compaq Computer Corporation</organization>
<address><email>mogul@wrl.dec.com</email></address>
</author>
<author initials="H." surname="Frystyk" fullname="H. Frystyk">
<organization>MIT Laboratory for Computer Science</organization>
<address><email>frystyk@w3.org</email></address>
</author>
<author initials="L." surname="Masinter" fullname="L. Masinter">
<organization>Xerox Corporation</organization>
<address><email>masinter@parc.xerox.com</email></address>
</author>
<author initials="P." surname="Leach" fullname="P. Leach">
<organization>Microsoft Corporation</organization>
<address><email>paulle@microsoft.com</email></address>
</author>
<author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
<organization>W3C</organization>
<address><email>timbl@w3.org</email></address>
</author>
<date month="June" year="1999"/>
</front>
<seriesInfo name="RFC" value="2616"/>
</reference>
<reference anchor="RFC2817">
<front>
<title>Upgrading to TLS Within HTTP/1.1</title>
<author initials="R." surname="Khare" fullname="R. Khare">
<organization>4K Associates / UC Irvine</organization>
<address><email>rohit@4K-associates.com</email></address>
</author>
<author initials="S." surname="Lawrence" fullname="S. Lawrence">
<organization>Agranat Systems, Inc.</organization>
<address><email>lawrence@agranat.com</email></address>
</author>
<date year="2000" month="May"/>
</front>
<seriesInfo name="RFC" value="2817"/>
</reference>
<reference anchor="RFC3864">
<front>
<title>Registration Procedures for Message Header Fields</title>
<author initials="G." surname="Klyne" fullname="G. Klyne">
<organization>Nine by Nine</organization>
<address><email>GK-IETF@ninebynine.org</email></address>
</author>
<author initials="M." surname="Nottingham" fullname="M. Nottingham">
<organization>BEA Systems</organization>
<address><email>mnot@pobox.com</email></address>
</author>
<author initials="J." surname="Mogul" fullname="J. Mogul">
<organization>HP Labs</organization>
<address><email>JeffMogul@acm.org</email></address>
</author>
<date year="2004" month="September"/>
</front>
<seriesInfo name="BCP" value="90"/>
<seriesInfo name="RFC" value="3864"/>
</reference>
<reference anchor="RFC5226">
<front>
<title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
<author initials="T." surname="Narten" fullname="T. Narten">
<organization>IBM</organization>
<address><email>narten@us.ibm.com</email></address>
</author>
<author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
<organization>Google</organization>
<address><email>Harald@Alvestrand.no</email></address>
</author>
<date year="2008" month="May"/>
</front>
<seriesInfo name="BCP" value="26"/>
<seriesInfo name="RFC" value="5226"/>
</reference>
<reference anchor="RFC5322">
<front>
<title>Internet Message Format</title>
<author initials="P." surname="Resnick" fullname="P. Resnick">
<organization>Qualcomm Incorporated</organization>
</author>
<date year="2008" month="October"/>
</front>
<seriesInfo name="RFC" value="5322"/>
</reference>
<reference anchor="RFC5789">
<front>
<title>PATCH Method for HTTP</title>
<author initials="L." surname="Dusseault" fullname="L. Dusseault">
<organization>Linden Lab</organization>
</author>
<author initials="J." surname="Snell" fullname="J. Snell"/>
<date year="2010" month="March"/>
</front>
<seriesInfo name="RFC" value="5789"/>
</reference>
</references>
<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
<t>
This document takes over the Status Code Registry, previously defined
in Section 7.1 of <xref target="RFC2817"/>.
(<xref target="status.code.registry"/>)
</t>
<t>
Clarify definition of POST.
(<xref target="POST"/>)
</t>
<t>
Remove requirement to handle all Content-* header fields; ban use of
Content-Range with PUT.
(<xref target="PUT"/>)
</t>
<t>
Take over definition of CONNECT method from <xref target="RFC2817"/>.
(<xref target="CONNECT"/>)
</t>
<t>
Failed to consider that there are
many other request methods that are safe to automatically redirect,
and further that the user agent is able to make that determination
based on the request method semantics.
(Sections <xref format="counter" target="status.301"/>,
<xref format="counter" target="status.302"/> and
<xref format="counter" target="status.307"/>)
</t>
<t>
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.
(<xref target="status.305"/>)
</t>
<t>
Define status 426 (Upgrade Required) (this was incorporated from
<xref target="RFC2817"/>).
(<xref target="status.426"/>)
</t>
<t>
Reclassify "Allow" as response header field, removing the option to
specify it in a PUT request.
Relax the server requirement on the contents of the Allow header field and
remove requirement on clients to always trust the header field value.
(<xref target="header.allow"/>)
</t>
<t>
Correct syntax of Location header field 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.
(<xref target="header.location"/>)
</t>
<t>
Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
extension methods could have used it as well).
(<xref target="header.max-forwards"/>)
</t>
<t>
Allow Referer field value of "about:blank" as alternative to not specifying it.
(<xref target="header.referer"/>)
</t>
<t>
In the description of the Server header field, the Via field
was described as a SHOULD. The requirement was and is stated
correctly in the description of the Via header field in Section 9.9 of <xref target="Part1"/>.
(<xref target="header.server"/>)
</t>
</section>
<section title="Collected ABNF" anchor="collected.abnf">
<figure>
<artwork type="abnf" name="p2-semantics.parsed-abnf"><![CDATA[
Allow = "Allow:" OWS Allow-v
Allow-v = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
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>
Location = "Location:" OWS Location-v
Location-v = URI-reference
Max-Forwards = "Max-Forwards:" OWS Max-Forwards-v
Max-Forwards-v = 1*DIGIT
Method = token
OWS = <OWS, defined in [Part1], Section 1.2.2>
RWS = <RWS, defined in [Part1], Section 1.2.2>
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 = 3DIGIT
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 ) )
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 ]
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>
token = <token, defined in [Part1], Section 1.2.2>
]]></artwork>
</figure>
<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
; Allow defined but not used
; Expect defined but not used
; From defined but not used
; Location defined but not used
; Max-Forwards defined but not used
; Reason-Phrase defined but not used
; Referer defined but not used
; Retry-After defined but not used
; Server defined but not used
; Status-Code defined but not used
; User-Agent defined but not used
]]></artwork></figure></section>
<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
<section title="Since RFC 2616">
<t>
Extracted relevant partitions from <xref target="RFC2616"/>.
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-00">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
"Via is a MUST"
(<eref target="http://purl.org/NET/http-errata#via-must"/>)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
"Fragments allowed in Location"
(<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
"Safe Methods vs Redirection"
(<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
"Revise description of the POST method"
(<eref target="http://purl.org/NET/http-errata#post"/>)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
"Normative and Informative references"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
"RFC2606 Compliance"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
"Informative references"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
"Redundant cross-references"
</t>
</list>
</t>
<t>
Other changes:
<list style="symbols">
<t>
Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-01">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
"PUT side effects"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
"Duplicate Host header requirements"
</t>
</list>
</t>
<t>
Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
<list style="symbols">
<t>
Move "Product Tokens" section (back) into Part 1, as "token" is used
in the definition of the Upgrade header field.
</t>
<t>
Add explicit references to BNF syntax and rules imported from other parts of the specification.
</t>
<t>
Copy definition of delta-seconds from Part6 instead of referencing it.
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
"Requiring Allow in 405 responses"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
"Status Code Registry"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
"Redirection vs. Location"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
"Cacheability of 303 response"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
"305 Use Proxy"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
"Classification for Allow header"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
"PUT - 'store under' vs 'store at'"
</t>
</list>
</t>
<t>
Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
<list style="symbols">
<t>
Reference RFC 3984, and update header field registrations for headers defined
in this document.
</t>
</list>
</t>
<t>
Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
<list style="symbols">
<t>
Replace string literals when the string really is case-sensitive (method).
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
"OPTIONS request bodies"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
"Description of CONNECT should refer to RFC2817"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
"Location Content-Location reference request/response mixup"
</t>
</list>
</t>
<t>
Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
<list style="symbols">
<t>
Added initial proposal for registration process, plus initial
content (non-HTTP/1.1 methods to be added by a separate specification).
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
"Content-*"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
"RFC 2822 is updated by RFC 5322"
</t>
</list>
</t>
<t>
Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
<list style="symbols">
<t>
Use "/" instead of "|" for alternatives.
</t>
<t>
Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
whitespace ("OWS") and required whitespace ("RWS").
</t>
<t>
Rewrite ABNFs to spell out whitespace rules, factor out
header field value format definitions.
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
"Reason-Phrase BNF"
</t>
</list>
</t>
<t>
Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
<list style="symbols">
<t>
Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
"Clarify when Referer is sent"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
"status codes vs methods"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
"Do not require "updates" relation for specs that register status codes or method names"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
"Idempotency"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
"TRACE security considerations"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
"Clarify rules for determining what entities a response carries"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
"update note citing RFC 1945 and 2068"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
"update note about redirect limit"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
"Location header ABNF should use 'URI'"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
"fragments in Location vs status 303"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
"move IANA registrations for optional status codes"
</t>
</list>
</t>
<t>
Partly resolved issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
"Are OPTIONS and TRACE safe?"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="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)
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
"Fragment combination / precedence during redirects"
</t>
</list>
</t>
<t>
Partly resolved issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
"Location header payload handling"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
"Term for the requested resource's URI"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
"Clarify 'Requested Variant'"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
"Clarify entity / representation / variant terminology"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
"Methods and Caching"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
"OPTIONS vs Max-Forwards"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
"Status codes and caching"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
"consider removing the 'changes from 2068' sections"
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
"Considerations for new status codes"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
"Considerations for new methods"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
"User-Agent guidelines" (relating to the 'User-Agent' header field)
</t>
</list>
</t>
</section>
<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
<t>
Closed issues:
<list style="symbols">
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
"Fragment combination / precedence during redirects" (added warning
about having a fragid on the redirect may cause inconvenience in
some cases)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
"Content-* vs. PUT"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
"205 Bodies"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
"Understanding Content-* on non-PUT requests"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
"Content-*"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
"Header type defaulting"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
"PUT - 'store under' vs 'store at'"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
"duplicate ABNF for Reason-Phrase"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
"Note special status of Content-* prefix in header registration procedures"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
"Max-Forwards vs extension methods"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
"What is the value space of HTTP status codes?" (actually fixed in
draft-ietf-httpbis-p2-semantics-11)
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
"Header Classification"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
"PUT side effect: invalidation or just stale?"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
"proxies not supporting certain methods"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
"Migrate CONNECT from RFC2817 to p2"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
"Migrate Upgrade details from RFC2817"
</t>
<t>
<eref target="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
"clarify PUT semantics'"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
"duplicate ABNF for 'Method'"
</t>
<t>
<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
"untangle ABNFs for header fields"
</t>
</list>
</t>
</section>
</section>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-23 13:12:33 |