source: draft-ietf-httpbis/11/p3-payload.xml @ 973

Last change on this file since 973 was 973, checked in by julian.reschke@…, 10 years ago

prepare publication of -11 drafts on 2010-08-04.

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File size: 135.5 KB
[29]1<?xml version="1.0" encoding="utf-8"?>
[101]2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
[8]3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns=''>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns=''>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns=''>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns=''>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns=''>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns=''>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns=''>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns=''>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns=''>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns=''>SHOULD NOT</bcp14>">
[973]14  <!ENTITY ID-VERSION "11">
[971]15  <!ENTITY ID-MONTH "August">
[741]16  <!ENTITY ID-YEAR "2010">
[424]17  <!ENTITY notation                 "<xref target='Part1' x:rel='#notation' xmlns:x=''/>">
[205]18  <!ENTITY notation-abnf            "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
19  <!ENTITY basic-rules              "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
[115]20  <!ENTITY caching-neg-resp         "<xref target='Part6' x:rel='#caching.negotiated.responses' xmlns:x=''/>">
[31]21  <!ENTITY header-transfer-encoding "<xref target='Part1' x:rel='#header.transfer-encoding' xmlns:x=''/>">
22  <!ENTITY header-content-length    "<xref target='Part1' x:rel='#header.content-length' xmlns:x=''/>">
23  <!ENTITY header-content-range     "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
24  <!ENTITY header-expires           "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
25  <!ENTITY header-last-modified     "<xref target='Part4' x:rel='#header.last-modified' xmlns:x=''/>">
26  <!ENTITY header-user-agent        "<xref target='Part2' x:rel='#header.user-agent' xmlns:x=''/>">
[115]27  <!ENTITY header-vary              "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
[31]28  <!ENTITY message-body             "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
[647]29  <!ENTITY header-fields            "<xref target='Part1' x:rel='#header.fields' xmlns:x=''/>">
[31]30  <!ENTITY multipart-byteranges     "<xref target='Part5' x:rel='' xmlns:x=''/>">
[580]31  <!ENTITY full-date                "<xref target='Part1' x:rel='' xmlns:x=''/>">
[457]32  <!ENTITY qvalue                   "<xref target='Part1' x:rel='#quality.values' xmlns:x=''/>">
[374]33  <!ENTITY uri                      "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
[823]34  <!ENTITY effective-request-uri    "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x=''/>">
[808]35  <!ENTITY compression-codings      "<xref target='Part1' x:rel='#compression.codings' xmlns:x=''/>">
36  <!ENTITY transfer-codings         "<xref target='Part1' x:rel='#transfer.codings' xmlns:x=''/>">
[673]37  <!ENTITY compress-coding          "<xref target='Part1' x:rel='#compress.coding' xmlns:x=''/>">
38  <!ENTITY deflate-coding           "<xref target='Part1' x:rel='#deflate.coding' xmlns:x=''/>">
39  <!ENTITY gzip-coding              "<xref target='Part1' x:rel='#gzip.coding' xmlns:x=''/>">
[716]40  <!ENTITY response-representation  "<xref target='Part2' x:rel='#identifying.response.associated.with.representation' xmlns:x=''/>">
42<?rfc toc="yes" ?>
[29]43<?rfc symrefs="yes" ?>
44<?rfc sortrefs="yes" ?>
[8]45<?rfc compact="yes"?>
46<?rfc subcompact="no" ?>
47<?rfc linkmailto="no" ?>
48<?rfc editing="no" ?>
[203]49<?rfc comments="yes"?>
50<?rfc inline="yes"?>
[799]51<?rfc rfcedstyle="yes"?>
[8]52<?rfc-ext allow-markup-in-artwork="yes" ?>
53<?rfc-ext include-references-in-index="yes" ?>
[308]54<rfc obsoletes="2616" category="std" x:maturity-level="draft"
[446]55     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-&ID-VERSION;"
[153]56     xmlns:x=''>
[120]59  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
[29]61  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
62    <organization abbrev="Day Software">Day Software</organization>
[8]63    <address>
64      <postal>
[29]65        <street>23 Corporate Plaza DR, Suite 280</street>
66        <city>Newport Beach</city>
[8]67        <region>CA</region>
[29]68        <code>92660</code>
69        <country>USA</country>
[8]70      </postal>
[29]71      <phone>+1-949-706-5300</phone>
72      <facsimile>+1-949-706-5305</facsimile>
73      <email></email>
74      <uri></uri>
[8]75    </address>
76  </author>
[29]78  <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]79    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
[8]80    <address>
81      <postal>
[29]82        <street>21 Oak Knoll Road</street>
83        <city>Carlisle</city>
[8]84        <region>MA</region>
[29]85        <code>01741</code>
86        <country>USA</country>
[8]87      </postal>
[844]88      <email></email>
89      <uri></uri>
[8]90    </address>
91  </author>
93  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
[29]94    <organization abbrev="HP">Hewlett-Packard Company</organization>
[8]95    <address>
96      <postal>
[29]97        <street>HP Labs, Large Scale Systems Group</street>
98        <street>1501 Page Mill Road, MS 1177</street>
[8]99        <city>Palo Alto</city>
100        <region>CA</region>
[29]101        <code>94304</code>
102        <country>USA</country>
[8]103      </postal>
[29]104      <email></email>
[8]105    </address>
106  </author>
108  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
[29]109    <organization abbrev="Microsoft">Microsoft Corporation</organization>
[8]110    <address>
111      <postal>
[29]112        <street>1 Microsoft Way</street>
113        <city>Redmond</city>
114        <region>WA</region>
115        <code>98052</code>
116        <country>USA</country>
[8]117      </postal>
[29]118      <email></email>
[8]119    </address>
120  </author>
122  <author initials="L." surname="Masinter" fullname="Larry Masinter">
[29]123    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
[8]124    <address>
125      <postal>
[29]126        <street>345 Park Ave</street>
127        <city>San Jose</city>
[8]128        <region>CA</region>
[29]129        <code>95110</code>
130        <country>USA</country>
[8]131      </postal>
[29]132      <email></email>
133      <uri></uri>
[8]134    </address>
135  </author>
137  <author initials="P." surname="Leach" fullname="Paul J. Leach">
138    <organization abbrev="Microsoft">Microsoft Corporation</organization>
139    <address>
140      <postal>
141        <street>1 Microsoft Way</street>
142        <city>Redmond</city>
143        <region>WA</region>
144        <code>98052</code>
145      </postal>
146      <email></email>
147    </address>
148  </author>
150  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
151    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
152    <address>
153      <postal>
[34]154        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
155        <street>The Stata Center, Building 32</street>
156        <street>32 Vassar Street</street>
[8]157        <city>Cambridge</city>
158        <region>MA</region>
159        <code>02139</code>
[29]160        <country>USA</country>
[8]161      </postal>
162      <email></email>
[34]163      <uri></uri>
[8]164    </address>
165  </author>
[95]167  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]168    <organization abbrev="W3C">World Wide Web Consortium</organization>
169    <address>
170      <postal>
171        <street>W3C / ERCIM</street>
172        <street>2004, rte des Lucioles</street>
173        <city>Sophia-Antipolis</city>
174        <region>AM</region>
175        <code>06902</code>
176        <country>France</country>
177      </postal>
178      <email></email>
179      <uri></uri>
180    </address>
181  </author>
[95]183  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
184    <organization abbrev="greenbytes">greenbytes GmbH</organization>
185    <address>
186      <postal>
187        <street>Hafenweg 16</street>
188        <city>Muenster</city><region>NW</region><code>48155</code>
189        <country>Germany</country>
190      </postal>
[609]191      <phone>+49 251 2807760</phone>
192      <facsimile>+49 251 2807761</facsimile>
193      <email></email>
194      <uri></uri>
[95]195    </address>
196  </author>
[973]198  <date month="&ID-MONTH;" year="&ID-YEAR;" day="4"/>
[440]199  <workgroup>HTTPbis Working Group</workgroup>
203   The Hypertext Transfer Protocol (HTTP) is an application-level
204   protocol for distributed, collaborative, hypermedia information
[29]205   systems. HTTP has been in use by the World Wide Web global information
[35]206   initiative since 1990. This document is Part 3 of the seven-part specification
[29]207   that defines the protocol referred to as "HTTP/1.1" and, taken together,
[42]208   obsoletes RFC 2616.  Part 3 defines HTTP message content,
[29]209   metadata, and content negotiation.
213<note title="Editorial Note (To be removed by RFC Editor)">
214  <t>
215    Discussion of this draft should take place on the HTTPBIS working group
216    mailing list ( The current issues list is
[848]217    at <eref target=""/>
[36]218    and related documents (including fancy diffs) can be found at
[324]219    <eref target=""/>.
[36]220  </t>
[153]221  <t>
[841]222    The changes in this draft are summarized in <xref target="changes.since.10"/>.
[153]223  </t>
227<section title="Introduction" anchor="introduction">
[163]229   This document defines HTTP/1.1 message payloads (a.k.a., content), the
[161]230   associated metadata header fields that define how the payload is intended
231   to be interpreted by a recipient, the request header fields that
[908]232   might influence content selection, and the various selection algorithms
[161]233   that are collectively referred to as HTTP content negotiation.
236   This document is currently disorganized in order to minimize the changes
237   between drafts and enable reviewers to see the smaller errata changes.
238   The next draft will reorganize the sections to better reflect the content.
239   In particular, the sections on entities will be renamed payload and moved
240   to the first half of the document, while the sections on content negotiation
241   and associated request header fields will be moved to the second half.  The
242   current mess reflects how widely dispersed these topics and associated
243   requirements had become in <xref target="RFC2616"/>.
[660]246<section title="Terminology" anchor="terminology">
248   This specification uses a number of terms to refer to the roles
249   played by participants in, and objects of, the HTTP communication.
252  <iref item="content negotiation"/>
253  <x:dfn>content negotiation</x:dfn>
254  <list>
255    <t>
256      The mechanism for selecting the appropriate representation when
[856]257      servicing a request. The representation in any response
[660]258      can be negotiated (including error responses).
259    </t>
260  </list>
[96]264<section title="Requirements" anchor="intro.requirements">
266   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
267   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
268   document are to be interpreted as described in <xref target="RFC2119"/>.
271   An implementation is not compliant if it fails to satisfy one or more
[847]272   of the "MUST" or "REQUIRED" level requirements for the protocols it
273   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
274   level and all the "SHOULD" level requirements for its protocols is said
275   to be "unconditionally compliant"; one that satisfies all the "MUST"
276   level requirements but not all the "SHOULD" level requirements for its
277   protocols is said to be "conditionally compliant".
[424]281<section title="Syntax Notation" anchor="notation">
[425]282  <x:anchor-alias value="ALPHA"/>
283  <x:anchor-alias value="CR"/>
284  <x:anchor-alias value="DIGIT"/>
285  <x:anchor-alias value="LF"/>
286  <x:anchor-alias value="OCTET"/>
287  <x:anchor-alias value="VCHAR"/>
288  <x:anchor-alias value="WSP"/>
[543]290  This specification uses the ABNF syntax defined in &notation; (which
291  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
292  <xref target="collected.abnf"/> shows the collected ABNF, with the list
293  rule expanded.
[425]296  The following core rules are included by
297  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
298  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
299  DIGIT (decimal 0-9), DQUOTE (double quote),
300  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
301  OCTET (any 8-bit sequence of data), SP (space),
302  VCHAR (any visible USASCII character),
303  and WSP (whitespace).
306<section title="Core Rules" anchor="core.rules">
[229]307  <x:anchor-alias value="quoted-string"/>
308  <x:anchor-alias value="token"/>
[810]309  <x:anchor-alias value="word"/>
[357]310  <x:anchor-alias value="OWS"/>
[424]312  The core rules below are defined in &basic-rules;:
314<figure><artwork type="abnf2616">
[229]315  <x:ref>quoted-string</x:ref>  = &lt;quoted-string, defined in &basic-rules;&gt;
316  <x:ref>token</x:ref>          = &lt;token, defined in &basic-rules;&gt;
[810]317  <x:ref>word</x:ref>           = &lt;word, defined in &basic-rules;&gt;
[357]318  <x:ref>OWS</x:ref>            = &lt;OWS, defined in &basic-rules;&gt;
322<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]323  <x:anchor-alias value="absolute-URI"/>
[229]324  <x:anchor-alias value="Allow"/>
325  <x:anchor-alias value="Content-Length"/>
326  <x:anchor-alias value="Content-Range"/>
327  <x:anchor-alias value="Expires"/>
328  <x:anchor-alias value="Last-Modified"/>
[647]329  <x:anchor-alias value="header-field"/>
[391]330  <x:anchor-alias value="partial-URI"/>
[457]331  <x:anchor-alias value="qvalue"/>
[206]333  The ABNF rules below are defined in other parts:
[207]335<figure><!--Part1--><artwork type="abnf2616">
[374]336  <x:ref>absolute-URI</x:ref>   = &lt;absolute-URI, defined in &uri;&gt;
[229]337  <x:ref>Content-Length</x:ref> = &lt;Content-Length, defined in &header-content-length;&gt;
[647]338  <x:ref>header-field</x:ref>   = &lt;header-field, defined in &header-fields;&gt;
[391]339  <x:ref>partial-URI</x:ref>    = &lt;partial-URI, defined in &uri;&gt;
[457]340  <x:ref>qvalue</x:ref>         = &lt;qvalue, defined in &qvalue;&gt;
342<figure><!--Part4--><artwork type="abnf2616">
[229]343  <x:ref>Last-Modified</x:ref>  = &lt;Last-Modified, defined in &header-last-modified;&gt;
345<figure><!--Part5--><artwork type="abnf2616">
[229]346  <x:ref>Content-Range</x:ref>  = &lt;Content-Range, defined in &header-content-range;&gt;
348<figure><!--Part6--><artwork type="abnf2616">
[229]349  <x:ref>Expires</x:ref>        = &lt;Expires, defined in &header-expires;&gt;
[8]357<section title="Protocol Parameters" anchor="protocol.parameters">
359<section title="Character Sets" anchor="character.sets">
361   HTTP uses the same definition of the term "character set" as that
362   described for MIME:
365   The term "character set" is used in this document to refer to a
366   method used with one or more tables to convert a sequence of octets
367   into a sequence of characters. Note that unconditional conversion in
[908]368   the other direction is not required, in that not all characters might
369   be available in a given character set and a character set might provide
[8]370   more than one sequence of octets to represent a particular character.
371   This definition is intended to allow various kinds of character
372   encoding, from simple single-table mappings such as US-ASCII to
373   complex table switching methods such as those that use ISO-2022's
374   techniques. However, the definition associated with a MIME character
375   set name &MUST; fully specify the mapping to be performed from octets
376   to characters. In particular, use of external profiling information
377   to determine the exact mapping is not permitted.
380  <t>
381    <x:h>Note:</x:h> This use of the term "character set" is more commonly
[879]382    referred to as a "character encoding". However, since HTTP and
[563]383    MIME share the same registry, it is important that the terminology
384    also be shared.
385  </t>
[229]387<t anchor="rule.charset">
388  <x:anchor-alias value="charset"/>
[8]389   HTTP character sets are identified by case-insensitive tokens. The
390   complete set of tokens is defined by the IANA Character Set registry
[91]391   (<eref target=""/>).
393<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="charset"/>
[229]394  <x:ref>charset</x:ref> = <x:ref>token</x:ref>
397   Although HTTP allows an arbitrary token to be used as a charset
398   value, any token that has a predefined value within the IANA
[91]399   Character Set registry &MUST; represent the character set defined
[8]400   by that registry. Applications &SHOULD; limit their use of character
401   sets to those defined by the IANA registry.
[81]404   HTTP uses charset in two contexts: within an Accept-Charset request
405   header (in which the charset value is an unquoted token) and as the
[115]406   value of a parameter in a Content-Type header (within a request or
[81]407   response), in which case the parameter value of the charset parameter
[908]408   can be quoted.
[969]411   Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
[8]412   <xref target="RFC2277"/>.
415<section title="Missing Charset" anchor="missing.charset">
417   Some HTTP/1.0 software has interpreted a Content-Type header without
[879]418   charset parameter incorrectly to mean "recipient should guess".
[211]419   Senders wishing to defeat this behavior &MAY; include a charset
420   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and &SHOULD; do so when
421   it is known that it will not confuse the recipient.
424   Unfortunately, some older HTTP/1.0 clients did not deal properly with
425   an explicit charset parameter. HTTP/1.1 recipients &MUST; respect the
426   charset label provided by the sender; and those user agents that have
427   a provision to "guess" a charset &MUST; use the charset from the
428   content-type field if they support that charset, rather than the
429   recipient's preference, when initially displaying a document. See
430   <xref target="canonicalization.and.text.defaults"/>.
435<section title="Content Codings" anchor="content.codings">
[229]436  <x:anchor-alias value="content-coding"/>
438   Content coding values indicate an encoding transformation that has
[866]439   been or can be applied to a representation. Content codings are primarily
440   used to allow a representation to be compressed or otherwise usefully
[8]441   transformed without losing the identity of its underlying media type
[866]442   and without loss of information. Frequently, the representation is stored in
[8]443   coded form, transmitted directly, and only decoded by the recipient.
445<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-coding"/>
[229]446  <x:ref>content-coding</x:ref>   = <x:ref>token</x:ref>
449   All content-coding values are case-insensitive. HTTP/1.1 uses
450   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
451   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
452   describes the content-coding, what is more important is that it
453   indicates what decoding mechanism will be required to remove the
454   encoding.
[673]457   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
458  <list>
459    <t>
460      See &compress-coding;.
461    </t>
462  </list>
[673]465   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
[8]466  <list>
467    <t>
[673]468      See &deflate-coding;.
[8]469    </t>
470  </list>
[673]473   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
474  <list>
475    <t>
476      See &gzip-coding;.
477    </t>
478  </list>
[673]481   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
[8]482  <list><t>
483        The default (identity) encoding; the use of no transformation
484        whatsoever. This content-coding is used only in the Accept-Encoding
485        header, and &SHOULD-NOT;  be used in the Content-Encoding
486        header.
487  </t></list>
490<section title="Content Coding Registry" anchor="content.coding.registry">
[670]492   The HTTP Content Coding Registry defines the name space for the content
493   coding names.
496   Registrations &MUST; include the following fields:
497   <list style="symbols">
498     <t>Name</t>
499     <t>Description</t>
500     <t>Pointer to specification text</t>
501   </list>
[808]504   Names of content codings &MUST-NOT; overlap with names of transfer codings
505   (&transfer-codings;), unless the encoding transformation is identical (as it
506   is the case for the compression codings defined in
507   &compression-codings;).
[942]510   Values to be added to this name space require a specification
511   (see "Specification Required" in
[670]512   <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
[8]513   conform to the purpose of content coding defined in this section.
516   The registry itself is maintained at
517   <eref target=""/>.
[8]523<section title="Media Types" anchor="media.types">
[229]524  <x:anchor-alias value="media-type"/>
525  <x:anchor-alias value="type"/>
526  <x:anchor-alias value="subtype"/>
[152]528   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
[8]529   and Accept (<xref target="header.accept"/>) header fields in order to provide
530   open and extensible data typing and type negotiation.
532<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="media-type"/><iref primary="true" item="Grammar" subitem="type"/><iref primary="true" item="Grammar" subitem="subtype"/>
[357]533  <x:ref>media-type</x:ref> = <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
534  <x:ref>type</x:ref>       = <x:ref>token</x:ref>
535  <x:ref>subtype</x:ref>    = <x:ref>token</x:ref>
[229]537<t anchor="rule.parameter">
538  <x:anchor-alias value="attribute"/>
539  <x:anchor-alias value="parameter"/>
540  <x:anchor-alias value="value"/>
[8]541   Parameters &MAY; follow the type/subtype in the form of attribute/value
[29]542   pairs.
[29]544<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="parameter"/><iref primary="true" item="Grammar" subitem="attribute"/><iref primary="true" item="Grammar" subitem="value"/>
[250]545  <x:ref>parameter</x:ref>      = <x:ref>attribute</x:ref> "=" <x:ref>value</x:ref>
546  <x:ref>attribute</x:ref>      = <x:ref>token</x:ref>
[810]547  <x:ref>value</x:ref>          = <x:ref>word</x:ref>
550   The type, subtype, and parameter attribute names are case-insensitive.
[370]551   Parameter values might or might not be case-sensitive, depending on the
552   semantics of the parameter name.  The presence or absence of a parameter might
[8]553   be significant to the processing of a media-type, depending on its
554   definition within the media type registry.
[908]557   A parameter value that matches the <x:ref>token</x:ref> production can be
[297]558   transmitted as either a token or within a quoted-string. The quoted and
559   unquoted values are equivalent.
[8]562   Note that some older HTTP applications do not recognize media type
563   parameters. When sending data to older HTTP applications,
564   implementations &SHOULD; only use media type parameters when they are
565   required by that type/subtype definition.
568   Media-type values are registered with the Internet Assigned Number
[91]569   Authority (IANA). The media type registration process is
[115]570   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
[8]571   discouraged.
574<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
[874]576   Internet media types are registered with a canonical form. A
577   representation transferred via HTTP messages &MUST; be in the
[8]578   appropriate canonical form prior to its transmission except for
579   "text" types, as defined in the next paragraph.
582   When in canonical form, media subtypes of the "text" type use CRLF as
583   the text line break. HTTP relaxes this requirement and allows the
584   transport of text media with plain CR or LF alone representing a line
[874]585   break when it is done consistently for an entire representation. HTTP
586   applications &MUST; accept CRLF, bare CR, and bare LF as indicating
587   a line break in text media received via HTTP. In
588   addition, if the text is in a character encoding that does not
[8]589   use octets 13 and 10 for CR and LF respectively, as is the case for
[874]590   some multi-byte character encodings, HTTP allows the use of whatever octet
591   sequences are defined by that character encoding to represent the
[8]592   equivalent of CR and LF for line breaks. This flexibility regarding
[874]593   line breaks applies only to text media in the payload body; a bare CR
[8]594   or LF &MUST-NOT; be substituted for CRLF within any of the HTTP control
595   structures (such as header fields and multipart boundaries).
[874]598   If a representation is encoded with a content-coding, the underlying
[8]599   data &MUST; be in a form defined above prior to being encoded.
[211]602   The "charset" parameter is used with some media types to define the
[874]603   character encoding (<xref target="character.sets"/>) of the data. When no explicit charset
[211]604   parameter is provided by the sender, media subtypes of the "text"
605   type are defined to have a default charset value of "ISO-8859-1" when
[874]606   received via HTTP. Data in character encodings other than "ISO-8859-1" or
[211]607   its subsets &MUST; be labeled with an appropriate charset value. See
608   <xref target="missing.charset"/> for compatibility problems.
612<section title="Multipart Types" anchor="multipart.types">
614   MIME provides for a number of "multipart" types -- encapsulations of
[874]615   one or more representations within a single message-body. All multipart
[97]616   types share a common syntax, as defined in <xref target="RFC2046" x:sec="5.1.1" x:fmt="of"/>,
617   and &MUST; include a boundary parameter as part of the media type
[8]618   value. The message body is itself a protocol element and &MUST;
619   therefore use only CRLF to represent line breaks between body-parts.
622   In general, HTTP treats a multipart message-body no differently than
[852]623   any other media type: strictly as payload.  HTTP does not use the
624   multipart boundary as an indicator of message-body length.
[97]625   <!-- jre: re-insert removed text pointing to caching? -->
[852]626   In all other respects, an HTTP user agent &SHOULD; follow the same or similar
[8]627   behavior as a MIME user agent would upon receipt of a multipart type.
628   The MIME header fields within each body-part of a multipart message-body
629   do not have any significance to HTTP beyond that defined by
630   their MIME semantics.
633   If an application receives an unrecognized multipart subtype, the
634   application &MUST; treat it as being equivalent to "multipart/mixed".
637  <t>
638    <x:h>Note:</x:h> The "multipart/form-data" type has been specifically defined
639    for carrying form data suitable for processing via the POST
640    request method, as described in <xref target="RFC2388"/>.
641  </t>
646<section title="Language Tags" anchor="language.tags">
[229]647  <x:anchor-alias value="language-tag"/>
[690]649   A language tag, as defined in <xref target="RFC5646"/>, identifies a
[613]650   natural language spoken, written, or otherwise conveyed by human beings for
651   communication of information to other human beings. Computer languages are
652   explicitly excluded. HTTP uses language tags within the Accept-Language and
653   Content-Language fields.
[613]656   In summary, a language tag is composed of one or more parts: A primary
657   language subtag followed by a possibly empty series of subtags:
[613]659<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="language-tag"/>
[690]660  <x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in <xref target="RFC5646" x:sec="2.1"/>&gt;
663   White space is not allowed within the tag and all tags are case-insensitive.
[613]664   The name space of language subtags is administered by the IANA (see
665   <eref target=""/>).
668  <preamble>Example tags include:</preamble>
669<artwork type="example">
670  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
[690]674   See <xref target="RFC5646"/> for further information.
[965]679<section title="Payload" anchor="payload">
[965]681   HTTP messages &MAY; transfer a payload if not otherwise restricted by
682   the request method or response status code.  The payload consists of
683   metadata, in the form of header fields, and data, in the form of the
684   sequence of octets in the message-body after any transfer-coding has
685   been decoded.
[965]687<iref item="payload"/>
689   A "<x:dfn>payload</x:dfn>" in HTTP is always a partial or complete
690   representation of some resource.  We use separate terms for payload
691   and representation because some messages contain only the associated
692   representation's header fields (e.g., responses to HEAD) or only some
693   part(s) of the representation (e.g., the 206 status code).
695<section title="Payload Header Fields" anchor="payload.header.fields">
696  <x:anchor-alias value="payload-header"/>
[965]698   HTTP header fields that specifically define the payload, rather than the
699   associated representation, are referred to as "payload header fields".
700   The following payload header fields are defined by HTTP/1.1:
703   <x:ref>Content-Length</x:ref>           ; &header-content-length;
704   <x:ref>Content-MD5</x:ref>              ; <xref target="header.content-md5"/>
705   <x:ref>Content-Range</x:ref>            ; &header-content-range;
[874]709<section title="Payload Body" anchor="payload.body">
710  <x:anchor-alias value="payload-body"/>
[874]712   A payload body is only present in a message when a message-body is
713   present, as described in &message-body;. The payload body is obtained
[8]714   from the message-body by decoding any Transfer-Encoding that might
715   have been applied to ensure safe and proper transfer of the message.
[965]720<section title="Representation" anchor="representation">
721<iref item="representation"/>
[965]723   A "<x:dfn>representation</x:dfn>" is information in a format that can be readily
724   communicated from one party to another.  A resource representation
725   is information that reflects the state of that resource, as observed
726   at some point in the past (e.g., in a response to GET) or to be
727   desired at some point in the future (e.g., in a PUT request).
730   Most, but not all, representations transferred via HTTP are intended
731   to be a representation of the target resource (the resource identified
732   by the effective request URI).  The precise semantics of a representation
733   are determined by the type of message (request or response), the request
734   method, the response status code, and the representation metadata.
735   For example, the above semantic is true for the representation in any
736   200 (OK) response to GET and for the representation in any PUT request.
737   A 200 response to PUT, in contrast, contains either a representation
738   that describes the successful action or a representation of the target
739   resource, with the latter indicated by a Content-Location header field
740   with the same value as the effective request URI.  Likewise, response
741   messages with an error status code usually contain a representation that
742   describes the error and what next steps are suggested for resolving it.
745<section title="Representation Header Fields" anchor="representation.header.fields">
746  <x:anchor-alias value="representation-header"/>
748   Representation header fields define metadata about the representation data
749   enclosed in the message-body or, if no message-body is present, about
750   the representation that would have been transferred in a 200 response
751   to a simultaneous GET request with the same effective request URI.
754   The following header fields are defined as representation metadata:
757   <x:ref>Content-Encoding</x:ref>         ; <xref target="header.content-encoding"/>
758   <x:ref>Content-Language</x:ref>         ; <xref target="header.content-language"/>
759   <x:ref>Content-Location</x:ref>         ; <xref target="header.content-location"/>
760   <x:ref>Content-Type</x:ref>             ; <xref target="header.content-type"/>
761   <x:ref>Expires</x:ref>                  ; &header-expires;
762   <x:ref>Last-Modified</x:ref>            ; &header-last-modified;
766<section title="Representation Data" anchor="">
767  <x:anchor-alias value="representation-data"/>
769   The representation body associated with an HTTP message is
770   either provided as the payload body of the message or
771   referred to by the message semantics and the effective request
772   URI.  The representation data is in a format and encoding defined by
773   the representation metadata header fields.
776   The data type of the representation data
777   is determined via the header fields Content-Type and Content-Encoding.
[8]778   These define a two-layer, ordered encoding model:
780<figure><artwork type="example">
[965]781  representation-data := Content-Encoding( Content-Type( bits ) )
[965]784   Content-Type specifies the media type of the underlying data, which
785   defines both the data format and how that data &SHOULD; be processed
786   by the recipient (within the scope of the request method semantics).
787   Any HTTP/1.1 message containing a payload body &SHOULD; include a
788   Content-Type header field defining the media type of the associated
789   representation unless that metadata is unknown to the sender.
[831]790   If the Content-Type header field is not present, it indicates that
[965]791   the sender does not know the media type of the representation;
792   recipients &MAY; either assume that the media type is
793   "application/octet-stream" (<xref target="RFC2046" x:fmt="," x:sec="4.5.1"/>)
[592]794   or examine the content to determine its type.
[965]797   In practice, resource owners do not always properly configure their origin
798   server to provide the correct Content-Type for a given representation,
799   with the result that some clients will examine a response body's content
800   and override the specified type.
[908]801   Clients that do so risk drawing incorrect conclusions, which might expose
[965]802   additional security risks (e.g., "privilege escalation").  Furthermore,
803   it is impossible to determine the sender's intent by examining the data
804   format: many data formats match multiple media types that differ only in
805   processing semantics.  Implementers are encouraged to provide a means of
806   disabling such "content sniffing" when it is used.
[908]809   Content-Encoding is used to indicate any additional content
[8]810   codings applied to the data, usually for the purpose of data
[965]811   compression, that are a property of the representation.  If
812   Content-Encoding is not present, then there is no additional
813   encoding beyond that defined by the Content-Type.
818<section title="Content Negotiation" anchor="content.negotiation">
[745]820   HTTP responses include a representation which contains information for
821   interpretation, whether by a human user or for further processing.
822   Often, the server has different ways of representing the
823   same information; for example, in different formats, languages,
824   or using different character encodings.
[745]827   HTTP clients and their users might have different or variable
828   capabilities, characteristics or preferences which would influence
829   which representation, among those available from the server,
830   would be best for the server to deliver. For this reason, HTTP
831   provides mechanisms for "content negotiation" -- a process of
832   allowing selection of a representation of a given resource,
833   when more than one is available.
[745]836   This specification defines two patterns of content negotiation;
837   "server-driven", where the server selects the representation based
838   upon the client's stated preferences, and "agent-driven" negotiation,
839   where the server provides a list of representations for the client to
840   choose from, based upon their metadata. In addition,  there are
841   other patterns: some applications use an "active content" pattern,
842   where the server returns active content which runs on the client
843   and, based on client available parameters, selects additional
844   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
845   has also been proposed.
848   These patterns are all widely used, and have trade-offs in applicability
849   and practicality. In particular, when the number of preferences or
850   capabilities to be expressed by a client are large (such as when many
851   different formats are supported by a user-agent), server-driven
[908]852   negotiation becomes unwieldy, and might not be appropriate. Conversely,
[745]853   when the number of representations to choose from is very large,
[908]854   agent-driven negotiation might not be appropriate.
857   Note that in all cases, the supplier of representations has the
858   responsibility for determining which representations might be
859   considered to be the "same information".
862<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
864   If the selection of the best representation for a response is made by
865   an algorithm located at the server, it is called server-driven
866   negotiation. Selection is based on the available representations of
[763]867   the response (the dimensions over which it can vary; e.g., language,
[8]868   content-coding, etc.) and the contents of particular header fields in
869   the request message or on other information pertaining to the request
870   (such as the network address of the client).
873   Server-driven negotiation is advantageous when the algorithm for
874   selecting from among the available representations is difficult to
875   describe to the user agent, or when the server desires to send its
876   "best guess" to the client along with the first response (hoping to
877   avoid the round-trip delay of a subsequent request if the "best
878   guess" is good enough for the user). In order to improve the server's
879   guess, the user agent &MAY; include request header fields (Accept,
880   Accept-Language, Accept-Encoding, etc.) which describe its
881   preferences for such a response.
884   Server-driven negotiation has disadvantages:
885  <list style="numbers">
886    <t>
887         It is impossible for the server to accurately determine what
888         might be "best" for any given user, since that would require
889         complete knowledge of both the capabilities of the user agent
890         and the intended use for the response (e.g., does the user want
891         to view it on screen or print it on paper?).
892    </t>
893    <t>
894         Having the user agent describe its capabilities in every
895         request can be both very inefficient (given that only a small
896         percentage of responses have multiple representations) and a
897         potential violation of the user's privacy.
898    </t>
899    <t>
900         It complicates the implementation of an origin server and the
901         algorithms for generating responses to a request.
902    </t>
903    <t>
[908]904         It might limit a public cache's ability to use the same response
[8]905         for multiple user's requests.
906    </t>
907  </list>
910   HTTP/1.1 includes the following request-header fields for enabling
911   server-driven negotiation through description of user agent
912   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
913   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
[745]914   (<xref target="header.accept-language"/>), and User-Agent (&header-user-agent;).
915   However, an origin server is not limited to these dimensions and &MAY; vary
916   the response based on any aspect of the request, including information
[8]917   outside the request-header fields or within extension header fields
918   not defined by this specification.
921  <t>
922    <x:h>Note:</x:h> In practice, User-Agent based negotiation is fragile,
923    because new clients might not be recognized.
924  </t>
[115]927   The Vary header field (&header-vary;) can be used to express the parameters the
[8]928   server uses to select a representation that is subject to server-driven
[29]929   negotiation.
933<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
935   With agent-driven negotiation, selection of the best representation
936   for a response is performed by the user agent after receiving an
937   initial response from the origin server. Selection is based on a list
938   of the available representations of the response included within the
[874]939   header fields or body of the initial response, with each
[8]940   representation identified by its own URI. Selection from among the
[908]941   representations can be performed automatically (if the user agent is
[8]942   capable of doing so) or manually by the user selecting from a
943   generated (possibly hypertext) menu.
946   Agent-driven negotiation is advantageous when the response would vary
947   over commonly-used dimensions (such as type, language, or encoding),
948   when the origin server is unable to determine a user agent's
949   capabilities from examining the request, and generally when public
950   caches are used to distribute server load and reduce network usage.
953   Agent-driven negotiation suffers from the disadvantage of needing a
954   second request to obtain the best alternate representation. This
955   second request is only efficient when caching is used. In addition,
956   this specification does not define any mechanism for supporting
957   automatic selection, though it also does not prevent any such
958   mechanism from being developed as an extension and used within
959   HTTP/1.1.
[745]962   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
[8]963   status codes for enabling agent-driven negotiation when the server is
964   unwilling or unable to provide a varying response using server-driven
965   negotiation.
[8]970<section title="Header Field Definitions" anchor="header.fields">
[117]972   This section defines the syntax and semantics of HTTP/1.1 header fields
973   related to the payload of messages.
[8]976<section title="Accept" anchor="header.accept">
977  <iref primary="true" item="Accept header" x:for-anchor=""/>
978  <iref primary="true" item="Headers" subitem="Accept" x:for-anchor=""/>
[229]979  <x:anchor-alias value="Accept"/>
[357]980  <x:anchor-alias value="Accept-v"/>
[370]981  <x:anchor-alias value="accept-ext"/>
[229]982  <x:anchor-alias value="accept-params"/>
983  <x:anchor-alias value="media-range"/>
[698]985   The "Accept" request-header field can be used by user agents to specify
986   response media types that are acceptable. Accept headers can be used to
987   indicate that the request is specifically limited to a small set of desired
988   types, as in the case of a request for an in-line image.
[370]990<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="Accept-v"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/>
[366]991  <x:ref>Accept</x:ref>   = "Accept" ":" <x:ref>OWS</x:ref> <x:ref>Accept-v</x:ref>
[357]992  <x:ref>Accept-v</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
[229]994  <x:ref>media-range</x:ref>    = ( "*/*"
[334]995                   / ( <x:ref>type</x:ref> "/" "*" )
996                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
[370]997                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
998  <x:ref>accept-params</x:ref>  = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> *( <x:ref>accept-ext</x:ref> )
[376]999  <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref>
[810]1000                   [ "=" <x:ref>word</x:ref> ]
1003   The asterisk "*" character is used to group media types into ranges,
1004   with "*/*" indicating all media types and "type/*" indicating all
1005   subtypes of that type. The media-range &MAY; include media type
1006   parameters that are applicable to that range.
1009   Each media-range &MAY; be followed by one or more accept-params,
1010   beginning with the "q" parameter for indicating a relative quality
1011   factor. The first "q" parameter (if any) separates the media-range
1012   parameter(s) from the accept-params. Quality factors allow the user
1013   or user agent to indicate the relative degree of preference for that
[457]1014   media-range, using the qvalue scale from 0 to 1 (&qvalue;). The
[8]1015   default value is q=1.
1018  <t>
1019    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
1020    parameters from Accept extension parameters is due to historical
1021    practice. Although this prevents any media type parameter named
1022    "q" from being used with a media range, such an event is believed
1023    to be unlikely given the lack of any "q" parameters in the IANA
1024    media type registry and the rare usage of any media type
1025    parameters in Accept. Future media types are discouraged from
1026    registering any parameter named "q".
1027  </t>
1030   The example
1032<figure><artwork type="example">
[357]1033  Accept: audio/*; q=0.2, audio/basic
1036   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
[879]1037   type if it is the best available after an 80% mark-down in quality".
1040   If no Accept header field is present, then it is assumed that the
1041   client accepts all media types. If an Accept header field is present,
1042   and if the server cannot send a response which is acceptable
1043   according to the combined Accept field value, then the server &SHOULD;
[137]1044   send a 406 (Not Acceptable) response.
1047   A more elaborate example is
1049<figure><artwork type="example">
[357]1050  Accept: text/plain; q=0.5, text/html,
1051          text/x-dvi; q=0.8, text/x-c
1054   Verbally, this would be interpreted as "text/html and text/x-c are
1055   the preferred media types, but if they do not exist, then send the
[866]1056   text/x-dvi representation, and if that does not exist, send the text/plain
[879]1057   representation".
1060   Media ranges can be overridden by more specific media ranges or
1061   specific media types. If more than one media range applies to a given
1062   type, the most specific reference has precedence. For example,
1064<figure><artwork type="example">
[357]1065  Accept: text/*, text/html, text/html;level=1, */*
1068   have the following precedence:
[459]1069   <list style="numbers">
1070    <t>text/html;level=1</t>
1071    <t>text/html</t>
1072    <t>text/*</t>
1073    <t>*/*</t>
1074   </list>
1077   The media type quality factor associated with a given type is
1078   determined by finding the media range with the highest precedence
1079   which matches that type. For example,
1081<figure><artwork type="example">
[357]1082  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1083          text/html;level=2;q=0.4, */*;q=0.5
1086   would cause the following values to be associated:
[459]1088<texttable align="left">
1089  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1090  <c>text/html;level=1</c>    <c>1</c>
1091  <c>text/html</c>            <c>0.7</c>
1092  <c>text/plain</c>           <c>0.3</c>
1093  <c>image/jpeg</c>           <c>0.5</c>
1094  <c>text/html;level=2</c>    <c>0.4</c>
1095  <c>text/html;level=3</c>    <c>0.7</c>
1098      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
1099      values for certain media ranges. However, unless the user agent is
1100      a closed system which cannot interact with other rendering agents,
1101      this default set ought to be configurable by the user.
1105<section title="Accept-Charset" anchor="header.accept-charset">
1106  <iref primary="true" item="Accept-Charset header" x:for-anchor=""/>
1107  <iref primary="true" item="Headers" subitem="Accept-Charset" x:for-anchor=""/>
[229]1108  <x:anchor-alias value="Accept-Charset"/>
[357]1109  <x:anchor-alias value="Accept-Charset-v"/>
[698]1111   The "Accept-Charset" request-header field can be used by user agents to
1112   indicate what response character sets are acceptable. This field allows
[8]1113   clients capable of understanding more comprehensive or special-purpose
[698]1114   character sets to signal that capability to a server which is capable of
1115   representing documents in those character sets.
[357]1117<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/>
[366]1118  <x:ref>Accept-Charset</x:ref>   = "Accept-Charset" ":" <x:ref>OWS</x:ref>
[357]1119          <x:ref>Accept-Charset-v</x:ref>
[376]1120  <x:ref>Accept-Charset-v</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
1121                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1124   Character set values are described in <xref target="character.sets"/>. Each charset &MAY;
1125   be given an associated quality value which represents the user's
1126   preference for that charset. The default value is q=1. An example is
1128<figure><artwork type="example">
[357]1129  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1132   The special value "*", if present in the Accept-Charset field,
1133   matches every character set (including ISO-8859-1) which is not
1134   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1135   in an Accept-Charset field, then all character sets not explicitly
1136   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1137   a quality value of 1 if not explicitly mentioned.
1140   If no Accept-Charset header is present, the default is that any
1141   character set is acceptable. If an Accept-Charset header is present,
1142   and if the server cannot send a response which is acceptable
1143   according to the Accept-Charset header, then the server &SHOULD; send
[137]1144   an error response with the 406 (Not Acceptable) status code, though
[8]1145   the sending of an unacceptable response is also allowed.
1149<section title="Accept-Encoding" anchor="header.accept-encoding">
1150  <iref primary="true" item="Accept-Encoding header" x:for-anchor=""/>
1151  <iref primary="true" item="Headers" subitem="Accept-Encoding" x:for-anchor=""/>
[229]1152  <x:anchor-alias value="Accept-Encoding"/>
[357]1153  <x:anchor-alias value="Accept-Encoding-v"/>
[229]1154  <x:anchor-alias value="codings"/>
[698]1156   The "Accept-Encoding" request-header field can be used by user agents to
1157   indicate what response content-codings (<xref target="content.codings"/>)
1158   are acceptable in the response.
[357]1160<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="Accept-Encoding-v"/><iref primary="true" item="Grammar" subitem="codings"/>
[366]1161  <x:ref>Accept-Encoding</x:ref>    = "Accept-Encoding" ":" <x:ref>OWS</x:ref>
[357]1162                     <x:ref>Accept-Encoding-v</x:ref>
1163  <x:ref>Accept-Encoding-v</x:ref>  =
[370]1164                     #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[357]1165  <x:ref>codings</x:ref>            = ( <x:ref>content-coding</x:ref> / "*" )
[248]1168   Each codings value &MAY; be given an associated quality value which
1169   represents the preference for that encoding. The default value is q=1.
[8]1172   Examples of its use are:
1174<figure><artwork type="example">
[357]1175  Accept-Encoding: compress, gzip
1176  Accept-Encoding:
1177  Accept-Encoding: *
1178  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1179  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1182   A server tests whether a content-coding is acceptable, according to
1183   an Accept-Encoding field, using these rules:
1184  <list style="numbers">
1185      <t>If the content-coding is one of the content-codings listed in
1186         the Accept-Encoding field, then it is acceptable, unless it is
[457]1187         accompanied by a qvalue of 0. (As defined in &qvalue;, a
[879]1188         qvalue of 0 means "not acceptable".)</t>
1190      <t>The special "*" symbol in an Accept-Encoding field matches any
1191         available content-coding not explicitly listed in the header
1192         field.</t>
1194      <t>If multiple content-codings are acceptable, then the acceptable
1195         content-coding with the highest non-zero qvalue is preferred.</t>
1197      <t>The "identity" content-coding is always acceptable, unless
1198         specifically refused because the Accept-Encoding field includes
1199         "identity;q=0", or because the field includes "*;q=0" and does
1200         not explicitly include the "identity" content-coding. If the
1201         Accept-Encoding field-value is empty, then only the "identity"
1202         encoding is acceptable.</t>
1203  </list>
1206   If an Accept-Encoding field is present in a request, and if the
1207   server cannot send a response which is acceptable according to the
1208   Accept-Encoding header, then the server &SHOULD; send an error response
1209   with the 406 (Not Acceptable) status code.
1212   If no Accept-Encoding field is present in a request, the server &MAY;
1213   assume that the client will accept any content coding. In this case,
1214   if "identity" is one of the available content-codings, then the
1215   server &SHOULD; use the "identity" content-coding, unless it has
1216   additional information that a different content-coding is meaningful
1217   to the client.
1220  <t>
1221    <x:h>Note:</x:h> If the request does not include an Accept-Encoding field,
1222    and if the "identity" content-coding is unavailable, then
1223    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1224    "gzip" and "compress") are preferred; some older clients
1225    improperly display messages sent with other content-codings.  The
1226    server might also make this decision based on information about
1227    the particular user-agent or client.
1228  </t>
1231  <t>
1232    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
1233    associated with content-codings. This means that qvalues will not
1234    work and are not permitted with x-gzip or x-compress.
1235  </t>
1239<section title="Accept-Language" anchor="header.accept-language">
1240  <iref primary="true" item="Accept-Language header" x:for-anchor=""/>
1241  <iref primary="true" item="Headers" subitem="Accept-Language" x:for-anchor=""/>
[229]1242  <x:anchor-alias value="Accept-Language"/>
[357]1243  <x:anchor-alias value="Accept-Language-v"/>
[229]1244  <x:anchor-alias value="language-range"/>
[698]1246   The "Accept-Language" request-header field can be used by user agents to
1247   indicate the set of natural languages that are preferred in the response.
1248   Language tags are defined in <xref target="language.tags"/>.
[357]1250<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="Accept-Language-v"/><iref primary="true" item="Grammar" subitem="language-range"/>
[366]1251  <x:ref>Accept-Language</x:ref>   = "Accept-Language" ":" <x:ref>OWS</x:ref>
[357]1252                    <x:ref>Accept-Language-v</x:ref>
1253  <x:ref>Accept-Language-v</x:ref> =
[370]1254                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[357]1255  <x:ref>language-range</x:ref>    =
[303]1256            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
[303]1259   Each language-range can be given an associated quality value which
[8]1260   represents an estimate of the user's preference for the languages
1261   specified by that range. The quality value defaults to "q=1". For
1262   example,
1264<figure><artwork type="example">
[357]1265  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1268   would mean: "I prefer Danish, but will accept British English and
[879]1269   other types of English".
[724]1270   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
[724]1273   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
1274   several matching schemes. Implementations can offer the most appropriate
1275   matching scheme for their requirements.
1278  <t>
[756]1279    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
[724]1280    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
1281    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
[563]1282  </t>
1285   It might be contrary to the privacy expectations of the user to send
1286   an Accept-Language header with the complete linguistic preferences of
1287   the user in every request. For a discussion of this issue, see
1288   <xref target=""/>.
1291   As intelligibility is highly dependent on the individual user, it is
1292   recommended that client applications make the choice of linguistic
1293   preference available to the user. If the choice is not made
1294   available, then the Accept-Language header field &MUST-NOT; be given in
1295   the request.
1298  <t>
1299    <x:h>Note:</x:h> When making the choice of linguistic preference available to
1300    the user, we remind implementors of  the fact that users are not
1301    familiar with the details of language matching as described above,
[969]1302    and ought to be provided appropriate guidance. As an example, users
[563]1303    might assume that on selecting "en-gb", they will be served any
1304    kind of English document if British English is not available. A
1305    user agent might suggest in such a case to add "en" to get the
1306    best matching behavior.
1307  </t>
1311<section title="Content-Encoding" anchor="header.content-encoding">
1312  <iref primary="true" item="Content-Encoding header" x:for-anchor=""/>
1313  <iref primary="true" item="Headers" subitem="Content-Encoding" x:for-anchor=""/>
[229]1314  <x:anchor-alias value="Content-Encoding"/>
[357]1315  <x:anchor-alias value="Content-Encoding-v"/>
[965]1317   The "Content-Encoding" header field indicates what content-codings
[866]1318   have been applied to the representation, and thus what decoding mechanisms
[698]1319   must be applied in order to obtain the media-type referenced by the
1320   Content-Type header field. Content-Encoding is primarily used to allow a
[866]1321   representation to be compressed without losing the identity of its underlying
[698]1322   media type.
[357]1324<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/>
[366]1325  <x:ref>Content-Encoding</x:ref>   = "Content-Encoding" ":" <x:ref>OWS</x:ref> <x:ref>Content-Encoding-v</x:ref>
[357]1326  <x:ref>Content-Encoding-v</x:ref> = 1#<x:ref>content-coding</x:ref>
1329   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1331<figure><artwork type="example">
[357]1332  Content-Encoding: gzip
[866]1335   The content-coding is a characteristic of the representation.
1336   Typically, the representation body is stored with this
[8]1337   encoding and is only decoded before rendering or analogous usage.
1338   However, a non-transparent proxy &MAY; modify the content-coding if the
1339   new coding is known to be acceptable to the recipient, unless the
1340   "no-transform" cache-control directive is present in the message.
[866]1343   If the content-coding of a representation is not "identity", then the
1344   representation metadata &MUST; include a Content-Encoding header
1345   field (<xref target="header.content-encoding"/>)
[8]1346   that lists the non-identity content-coding(s) used.
[874]1349   If the content-coding of a representation in a request message is not
[8]1350   acceptable to the origin server, the server &SHOULD; respond with a
1351   status code of 415 (Unsupported Media Type).
[866]1354   If multiple encodings have been applied to a representation, the content
[8]1355   codings &MUST; be listed in the order in which they were applied.
1356   Additional information about the encoding parameters &MAY; be provided
[866]1357   by other header fields not defined by this specification.
1361<section title="Content-Language" anchor="header.content-language">
1362  <iref primary="true" item="Content-Language header" x:for-anchor=""/>
1363  <iref primary="true" item="Headers" subitem="Content-Language" x:for-anchor=""/>
[229]1364  <x:anchor-alias value="Content-Language"/>
[357]1365  <x:anchor-alias value="Content-Language-v"/>
[965]1367   The "Content-Language" header field describes the natural
[866]1368   language(s) of the intended audience for the representation. Note that this might
[874]1369   not be equivalent to all the languages used within the representation.
[357]1371<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/>
[366]1372  <x:ref>Content-Language</x:ref>   = "Content-Language" ":" <x:ref>OWS</x:ref> <x:ref>Content-Language-v</x:ref>
[357]1373  <x:ref>Content-Language-v</x:ref> = 1#<x:ref>language-tag</x:ref>
1376   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1377   Content-Language is to allow a user to identify and differentiate
[866]1378   representations according to the user's own preferred language. Thus, if the
[8]1379   body content is intended only for a Danish-literate audience, the
1380   appropriate field is
1382<figure><artwork type="example">
[357]1383  Content-Language: da
1386   If no Content-Language is specified, the default is that the content
1387   is intended for all language audiences. This might mean that the
1388   sender does not consider it to be specific to any natural language,
1389   or that the sender does not know for which language it is intended.
1392   Multiple languages &MAY; be listed for content that is intended for
1393   multiple audiences. For example, a rendition of the "Treaty of
[879]1394   Waitangi", presented simultaneously in the original Maori and English
[8]1395   versions, would call for
1397<figure><artwork type="example">
[357]1398  Content-Language: mi, en
[866]1401   However, just because multiple languages are present within a representation
[8]1402   does not mean that it is intended for multiple linguistic audiences.
1403   An example would be a beginner's language primer, such as "A First
[879]1404   Lesson in Latin", which is clearly intended to be used by an
[8]1405   English-literate audience. In this case, the Content-Language would
1406   properly only include "en".
1409   Content-Language &MAY; be applied to any media type -- it is not
1410   limited to textual documents.
1414<section title="Content-Location" anchor="header.content-location">
1415  <iref primary="true" item="Content-Location header" x:for-anchor=""/>
1416  <iref primary="true" item="Headers" subitem="Content-Location" x:for-anchor=""/>
[229]1417  <x:anchor-alias value="Content-Location"/>
[357]1418  <x:anchor-alias value="Content-Location-v"/>
[856]1420   The "Content-Location" header field supplies a URI that can be used
1421   as a specific identifier for the representation in this message.
1422   In other words, if one were to perform a GET on this URI at the time
1423   of this message's generation, then a 200 response would contain the
1424   same representation that is enclosed as payload in this message.
[357]1426<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/>
[366]1427  <x:ref>Content-Location</x:ref>   = "Content-Location" ":" <x:ref>OWS</x:ref>
[357]1428                    <x:ref>Content-Location-v</x:ref>
1429  <x:ref>Content-Location-v</x:ref> =
[391]1430                    <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
[972]1433   The Content-Location value is not a replacement for the effective
[856]1434   Request URI (&effective-request-uri;).  It is representation metadata.
1435   It has the same syntax and semantics as the header field of the same name
[858]1436   defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
[856]1437   However, its appearance in an HTTP message has some special implications
1438   for HTTP recipients.
[856]1441   If Content-Location is included in a response message and its value
[965]1442   is the same as the effective request URI, then the response payload
[856]1443   &SHOULD; be considered the current representation of that resource.
1444   For a GET or HEAD request, this is the same as the default semantics
1445   when no Content-Location is provided by the server.  For a state-changing
1446   method like PUT or POST, it implies that the server's response contains
1447   the new representation of that resource, thereby distinguishing it from
1448   representations that might only report about the action (e.g., "It worked!").
1449   This allows authoring applications to update their local copies without
1450   the need for a subsequent GET request.
[856]1453   If Content-Location is included in a response message and its value
[965]1454   differs from the effective request URI, then the origin server is
[856]1455   informing recipients that this representation has its own, presumably
1456   more specific, identifier.  For a GET or HEAD request, this is an
[965]1457   indication that the effective request URI identifies a resource that
[856]1458   is subject to content negotiation and the representation selected for
1459   this response can also be found at the identified URI.  For other
1460   methods, such a Content-Location indicates that this representation
1461   contains a report on the action's status and the same report is
1462   available (for future access with GET) at the given URI.  For
[908]1463   example, a purchase transaction made via the POST method might
[856]1464   include a receipt document as the payload of the 200 response;
1465   the Content-Location value provides an identifier for retrieving
1466   a copy of that same receipt in the future.
1469   If Content-Location is included in a request message, then it &MAY;
1470   be interpreted by the origin server as an indication of where the
1471   user agent originally obtained the content of the enclosed
1472   representation (prior to any subsequent modification of the content
1473   by that user agent).  In other words, the user agent is providing
1474   the same representation metadata that it received with the original
1475   representation.  However, such interpretation &MUST-NOT; be used to
1476   alter the semantics of the method requested by the client.  For
1477   example, if a client makes a PUT request on a negotiated resource
1478   and the origin server accepts that PUT (without redirection), then the
1479   new set of values for that resource is expected to be consistent with
1480   the one representation supplied in that PUT; the Content-Location
1481   cannot be used as a form of reverse content selection that
1482   identifies only one of the negotiated representations to be updated.
1483   If the user agent had wanted the latter semantics, it would have applied
1484   the PUT directly to the Content-Location URI.
1487   A Content-Location field received in a request message is transitory
1488   information that &SHOULD-NOT; be saved with other representation
1489   metadata for use in later responses.  The Content-Location's value
1490   might be saved for use in other contexts, such as within source links
1491   or other metadata.
1494   A cache cannot assume that a representation with a Content-Location
[8]1495   different from the URI used to retrieve it can be used to respond to
[856]1496   later requests on that Content-Location URI.
[965]1499   If the Content-Location value is a partial URI, the partial URI is
1500   interpreted relative to the effective request URI.
1504<section title="Content-MD5" anchor="header.content-md5">
1505  <iref primary="true" item="Content-MD5 header" x:for-anchor=""/>
1506  <iref primary="true" item="Headers" subitem="Content-MD5" x:for-anchor=""/>
[229]1507  <x:anchor-alias value="Content-MD5"/>
[357]1508  <x:anchor-alias value="Content-MD5-v"/>
[965]1510   The "Content-MD5" header field, as defined in <xref target="RFC1864"/>, is
[874]1511   an MD5 digest of the payload body that provides an end-to-end message
1512   integrity check (MIC) of the payload body (the message-body after any
1513   transfer-coding is decoded). Note that a MIC is good for
1514   detecting accidental modification of the payload body in transit, but is not
[699]1515   proof against malicious attacks.
[357]1517<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/>
[366]1518  <x:ref>Content-MD5</x:ref>   = "Content-MD5" ":" <x:ref>OWS</x:ref> <x:ref>Content-MD5-v</x:ref>
[357]1519  <x:ref>Content-MD5-v</x:ref> = &lt;base64 of 128 bit MD5 digest as per <xref target="RFC1864"/>&gt;
1522   The Content-MD5 header field &MAY; be generated by an origin server or
[874]1523   client to function as an integrity check of the payload body. Only
1524   origin servers or user agents &MAY; generate the Content-MD5 header field;
[8]1525   proxies and gateways &MUST-NOT; generate it, as this would defeat its
[874]1526   value as an end-to-end integrity check. Any recipient &MAY; check that
1527   the digest value in this header field matches a corresponding digest
1528   calculated on payload body as received.
[874]1531   The MD5 digest is computed based on the content of the payload body,
1532   including any content-coding, but not including any transfer-coding
1533   applied to the message-body because such transfer-codings might be
1534   applied or removed anywhere along the request/response chain.
1535   If the message is received with a transfer-coding, that encoding &MUST;
1536   be decoded prior to checking the Content-MD5 value against the received
1537   payload.
1540   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1541   composite media-types (e.g., multipart/* and message/rfc822), but
1542   this does not change how the digest is computed as defined in the
1543   preceding paragraph.
[874]1546   There are several consequences of this. The payload for composite
[8]1547   types &MAY; contain many body-parts, each with its own MIME and HTTP
1548   headers (including Content-MD5, Content-Transfer-Encoding, and
1549   Content-Encoding headers). If a body-part has a Content-Transfer-Encoding
1550   or Content-Encoding header, it is assumed that the content
1551   of the body-part has had the encoding applied, and the body-part is
1552   included in the Content-MD5 digest as is -- i.e., after the
1553   application. The Transfer-Encoding header field is not allowed within
1554   body-parts.
1557   Conversion of all line breaks to CRLF &MUST-NOT; be done before
1558   computing or checking the digest: the line break convention used in
1559   the text actually transmitted &MUST; be left unaltered when computing
1560   the digest.
1563  <t>
[756]1564    <x:h>Note:</x:h> While the definition of Content-MD5 is exactly the same for
[563]1565    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1566    in which the application of Content-MD5 to HTTP entity-bodies
1567    differs from its application to MIME entity-bodies. One is that
1568    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1569    does use Transfer-Encoding and Content-Encoding. Another is that
1570    HTTP more frequently uses binary content types than MIME, so it is
1571    worth noting that, in such cases, the byte order used to compute
1572    the digest is the transmission byte order defined for the type.
1573    Lastly, HTTP allows transmission of text types with any of several
1574    line break conventions and not just the canonical form using CRLF.
1575  </t>
1579<section title="Content-Type" anchor="header.content-type">
1580  <iref primary="true" item="Content-Type header" x:for-anchor=""/>
1581  <iref primary="true" item="Headers" subitem="Content-Type" x:for-anchor=""/>
[229]1582  <x:anchor-alias value="Content-Type"/>
[357]1583  <x:anchor-alias value="Content-Type-v"/>
[965]1585   The "Content-Type" header field indicates the media type of the
[874]1586   representation. In the case of responses to the HEAD method, the media type is
[698]1587   that which would have been sent had the request been a GET.
[357]1589<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/>
[366]1590  <x:ref>Content-Type</x:ref>   = "Content-Type" ":" <x:ref>OWS</x:ref> <x:ref>Content-Type-v</x:ref>
[357]1591  <x:ref>Content-Type-v</x:ref> = <x:ref>media-type</x:ref>
1594   Media types are defined in <xref target="media.types"/>. An example of the field is
1596<figure><artwork type="example">
[357]1597  Content-Type: text/html; charset=ISO-8859-4
[965]1600   Further discussion of Content-Type is provided in <xref target=""/>.
[29]1606<section title="IANA Considerations" anchor="IANA.considerations">
[921]1607<section title="Header Field Registration" anchor="header.field.registration">
[969]1609   The Message Header Field Registry located at <eref target=""/> shall be updated
[290]1610   with the permanent registrations below (see <xref target="RFC3864"/>):
[680]1612<?BEGININC p3-payload.iana-headers ?>
[253]1613<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]1614<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]1615   <ttcol>Header Field Name</ttcol>
1616   <ttcol>Protocol</ttcol>
1617   <ttcol>Status</ttcol>
1618   <ttcol>Reference</ttcol>
1620   <c>Accept</c>
1621   <c>http</c>
1622   <c>standard</c>
1623   <c>
1624      <xref target="header.accept"/>
1625   </c>
1626   <c>Accept-Charset</c>
1627   <c>http</c>
1628   <c>standard</c>
1629   <c>
1630      <xref target="header.accept-charset"/>
1631   </c>
1632   <c>Accept-Encoding</c>
1633   <c>http</c>
1634   <c>standard</c>
1635   <c>
1636      <xref target="header.accept-encoding"/>
1637   </c>
1638   <c>Accept-Language</c>
1639   <c>http</c>
1640   <c>standard</c>
1641   <c>
1642      <xref target="header.accept-language"/>
1643   </c>
1644   <c>Content-Disposition</c>
1645   <c>http</c>
[937]1646   <c>standard</c>
[253]1647   <c>
1648      <xref target="content-disposition"/>
1649   </c>
1650   <c>Content-Encoding</c>
1651   <c>http</c>
1652   <c>standard</c>
1653   <c>
1654      <xref target="header.content-encoding"/>
1655   </c>
1656   <c>Content-Language</c>
1657   <c>http</c>
1658   <c>standard</c>
1659   <c>
1660      <xref target="header.content-language"/>
1661   </c>
1662   <c>Content-Location</c>
1663   <c>http</c>
1664   <c>standard</c>
1665   <c>
1666      <xref target="header.content-location"/>
1667   </c>
1668   <c>Content-MD5</c>
1669   <c>http</c>
1670   <c>standard</c>
1671   <c>
1672      <xref target="header.content-md5"/>
1673   </c>
1674   <c>Content-Type</c>
1675   <c>http</c>
1676   <c>standard</c>
1677   <c>
1678      <xref target="header.content-type"/>
1679   </c>
[291]1680   <c>MIME-Version</c>
1681   <c>http</c>
[937]1682   <c>standard</c>
[291]1683   <c>
1684      <xref target="mime-version"/>
1685   </c>
[680]1688<?ENDINC p3-payload.iana-headers ?>
[290]1690   The change controller is: "IETF ( - Internet Engineering Task Force".
[668]1694<section title="Content Coding Registry" anchor="content.coding.registration">
1696   The registration procedure for HTTP Content Codings is now defined
[670]1697   by <xref target="content.coding.registry"/> of this document.
1700   The HTTP Content Codings Registry located at <eref target=""/>
[969]1701   shall be updated with the registration below:
1703<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
[670]1704   <ttcol>Name</ttcol>
[668]1705   <ttcol>Description</ttcol>
1706   <ttcol>Reference</ttcol>
1707   <c>compress</c>
1708   <c>UNIX "compress" program method</c>
1709   <c>
[673]1710      &compress-coding;
[668]1711   </c>
1712   <c>deflate</c>
[806]1713   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1714   the "zlib" data format (<xref target="RFC1950"/>)
1715   </c>
[668]1716   <c>
[673]1717      &deflate-coding;
[668]1718   </c>
1719   <c>gzip</c>
1720   <c>Same as GNU zip <xref target="RFC1952"/></c>
1721   <c>
[673]1722      &gzip-coding;
[668]1723   </c>
1724   <c>identity</c>
1725   <c>No transformation</c>
1726   <c>
1727      <xref target="content.codings"/>
1728   </c>
[8]1734<section title="Security Considerations" anchor="security.considerations">
1736   This section is meant to inform application developers, information
1737   providers, and users of the security limitations in HTTP/1.1 as
1738   described by this document. The discussion does not include
1739   definitive solutions to the problems revealed, though it does make
1740   some suggestions for reducing security risks.
1743<section title="Privacy Issues Connected to Accept Headers" anchor="">
1745   Accept request-headers can reveal information about the user to all
1746   servers which are accessed. The Accept-Language header in particular
1747   can reveal information the user would consider to be of a private
1748   nature, because the understanding of particular languages is often
1749   strongly correlated to the membership of a particular ethnic group.
1750   User agents which offer the option to configure the contents of an
1751   Accept-Language header to be sent in every request are strongly
1752   encouraged to let the configuration process include a message which
1753   makes the user aware of the loss of privacy involved.
1756   An approach that limits the loss of privacy would be for a user agent
1757   to omit the sending of Accept-Language headers by default, and to ask
1758   the user whether or not to start sending Accept-Language headers to a
1759   server if it detects, by looking for any Vary response-header fields
1760   generated by the server, that such sending could improve the quality
1761   of service.
1764   Elaborate user-customized accept header fields sent in every request,
1765   in particular if these include quality values, can be used by servers
1766   as relatively reliable and long-lived user identifiers. Such user
1767   identifiers would allow content providers to do click-trail tracking,
1768   and would allow collaborating content providers to match cross-server
1769   click-trails or form submissions of individual users. Note that for
1770   many users not behind a proxy, the network address of the host
1771   running the user agent will also serve as a long-lived user
1772   identifier. In environments where proxies are used to enhance
1773   privacy, user agents ought to be conservative in offering accept
1774   header configuration options to end users. As an extreme privacy
1775   measure, proxies could filter the accept headers in relayed requests.
1776   General purpose user agents which provide a high degree of header
1777   configurability &SHOULD; warn users about the loss of privacy which can
1778   be involved.
1782<section title="Content-Disposition Issues" anchor="content-disposition.issues">
[269]1784   <xref target="RFC2183"/>, from which the often implemented Content-Disposition
[8]1785   (see <xref target="content-disposition"/>) header in HTTP is derived, has a number of very
1786   serious security considerations. Content-Disposition is not part of
1787   the HTTP standard, but since it is widely implemented, we are
[269]1788   documenting its use and risks for implementors. See <xref target="RFC2183" x:fmt="of" x:sec="5"/>
1789   for details.
1795<section title="Acknowledgments" anchor="ack">
[119]1800<references title="Normative References">
[121]1802<reference anchor="ISO-8859-1">
1803  <front>
1804    <title>
1805     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1806    </title>
1807    <author>
1808      <organization>International Organization for Standardization</organization>
1809    </author>
1810    <date year="1998"/>
1811  </front>
1812  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
[31]1815<reference anchor="Part1">
[119]1816  <front>
1817    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1818    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1819      <organization abbrev="Day Software">Day Software</organization>
1820      <address><email></email></address>
1821    </author>
1822    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1823      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1824      <address><email></email></address>
[119]1825    </author>
1826    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1827      <organization abbrev="HP">Hewlett-Packard Company</organization>
1828      <address><email></email></address>
1829    </author>
1830    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1831      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1832      <address><email></email></address>
1833    </author>
1834    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1835      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1836      <address><email></email></address>
1837    </author>
1838    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1839      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1840      <address><email></email></address>
1841    </author>
1842    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1843      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1844      <address><email></email></address>
1845    </author>
1846    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1847      <organization abbrev="W3C">World Wide Web Consortium</organization>
1848      <address><email></email></address>
1849    </author>
1850    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1851      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1852      <address><email></email></address>
1853    </author>
1854    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1855  </front>
1856  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1857  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1860<reference anchor="Part2">
[119]1861  <front>
1862    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1863    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1864      <organization abbrev="Day Software">Day Software</organization>
1865      <address><email></email></address>
1866    </author>
1867    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1868      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1869      <address><email></email></address>
[119]1870    </author>
1871    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1872      <organization abbrev="HP">Hewlett-Packard Company</organization>
1873      <address><email></email></address>
1874    </author>
1875    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1876      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1877      <address><email></email></address>
1878    </author>
1879    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1880      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1881      <address><email></email></address>
1882    </author>
1883    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1884      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1885      <address><email></email></address>
1886    </author>
1887    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1888      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1889      <address><email></email></address>
1890    </author>
1891    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1892      <organization abbrev="W3C">World Wide Web Consortium</organization>
1893      <address><email></email></address>
1894    </author>
1895    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1896      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1897      <address><email></email></address>
1898    </author>
1899    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1900  </front>
1901  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
1902  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
1905<reference anchor="Part4">
[119]1906  <front>
1907    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1908    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1909      <organization abbrev="Day Software">Day Software</organization>
1910      <address><email></email></address>
1911    </author>
1912    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1913      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1914      <address><email></email></address>
[119]1915    </author>
1916    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1917      <organization abbrev="HP">Hewlett-Packard Company</organization>
1918      <address><email></email></address>
1919    </author>
1920    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1921      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1922      <address><email></email></address>
1923    </author>
1924    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1925      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1926      <address><email></email></address>
1927    </author>
1928    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1929      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1930      <address><email></email></address>
1931    </author>
1932    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1933      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1934      <address><email></email></address>
1935    </author>
1936    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1937      <organization abbrev="W3C">World Wide Web Consortium</organization>
1938      <address><email></email></address>
1939    </author>
1940    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1941      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1942      <address><email></email></address>
1943    </author>
1944    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1945  </front>
1946  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1947  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1950<reference anchor="Part5">
[119]1951  <front>
1952    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1953    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1954      <organization abbrev="Day Software">Day Software</organization>
1955      <address><email></email></address>
1956    </author>
1957    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1958      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1959      <address><email></email></address>
[119]1960    </author>
1961    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1962      <organization abbrev="HP">Hewlett-Packard Company</organization>
1963      <address><email></email></address>
1964    </author>
1965    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1966      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1967      <address><email></email></address>
1968    </author>
1969    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1970      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1971      <address><email></email></address>
1972    </author>
1973    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1974      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1975      <address><email></email></address>
1976    </author>
1977    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1978      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1979      <address><email></email></address>
1980    </author>
1981    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1982      <organization abbrev="W3C">World Wide Web Consortium</organization>
1983      <address><email></email></address>
1984    </author>
1985    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1986      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1987      <address><email></email></address>
1988    </author>
1989    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1990  </front>
1991  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
1992  <x:source href="p5-range.xml" basename="p5-range"/>
1995<reference anchor="Part6">
[119]1996  <front>
1997    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1998    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1999      <organization abbrev="Day Software">Day Software</organization>
2000      <address><email></email></address>
2001    </author>
2002    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]2003      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2004      <address><email></email></address>
[119]2005    </author>
2006    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2007      <organization abbrev="HP">Hewlett-Packard Company</organization>
2008      <address><email></email></address>
2009    </author>
2010    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2011      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2012      <address><email></email></address>
2013    </author>
2014    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2015      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2016      <address><email></email></address>
2017    </author>
2018    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2019      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2020      <address><email></email></address>
2021    </author>
2022    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2023      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2024      <address><email></email></address>
2025    </author>
2026    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2027      <organization abbrev="W3C">World Wide Web Consortium</organization>
2028      <address><email></email></address>
2029    </author>
[601]2030    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2031      <address><email></email></address>
2032    </author>
[119]2033    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2034      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2035      <address><email></email></address>
2036    </author>
2037    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2038  </front>
2039  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2040  <x:source href="p6-cache.xml" basename="p6-cache"/>
[131]2043<reference anchor="RFC1864">
2044  <front>
2045    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
2046    <author initials="J." surname="Myers" fullname="John G. Myers">
2047      <organization>Carnegie Mellon University</organization>
2048      <address><email></email></address>
2049    </author>
2050    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
2051      <organization>Dover Beach Consulting, Inc.</organization>
2052      <address><email></email></address>
2053    </author>
2054    <date month="October" year="1995"/>
2055  </front>
2056  <seriesInfo name="RFC" value="1864"/>
[122]2059<reference anchor="RFC1950">
2060  <front>
2061    <title>ZLIB Compressed Data Format Specification version 3.3</title>
2062    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2063      <organization>Aladdin Enterprises</organization>
2064      <address><email></email></address>
2065    </author>
[713]2066    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
[122]2067    <date month="May" year="1996"/>
2068  </front>
2069  <seriesInfo name="RFC" value="1950"/>
2070  <annotation>
[908]2071    RFC 1950 is an Informational RFC, thus it might be less stable than
[122]2072    this specification. On the other hand, this downward reference was
[277]2073    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2074    therefore it is unlikely to cause problems in practice. See also
2075    <xref target="BCP97"/>.
[122]2076  </annotation>
[806]2079<reference anchor="RFC1951">
2080  <front>
2081    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
2082    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2083      <organization>Aladdin Enterprises</organization>
2084      <address><email></email></address>
2085    </author>
2086    <date month="May" year="1996"/>
2087  </front>
2088  <seriesInfo name="RFC" value="1951"/>
2089  <annotation>
[908]2090    RFC 1951 is an Informational RFC, thus it might be less stable than
[806]2091    this specification. On the other hand, this downward reference was
2092    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2093    therefore it is unlikely to cause problems in practice. See also
2094    <xref target="BCP97"/>.
2095  </annotation>
[122]2098<reference anchor="RFC1952">
2099  <front>
2100    <title>GZIP file format specification version 4.3</title>
2101    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2102      <organization>Aladdin Enterprises</organization>
2103      <address><email></email></address>
2104    </author>
2105    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2106      <address><email></email></address>
2107    </author>
2108    <author initials="M." surname="Adler" fullname="Mark Adler">
2109      <address><email></email></address>
2110    </author>
2111    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2112      <address><email></email></address>
2113    </author>
2114    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2115      <address><email></email></address>
2116    </author>
2117    <date month="May" year="1996"/>
2118  </front>
2119  <seriesInfo name="RFC" value="1952"/>
2120  <annotation>
[908]2121    RFC 1952 is an Informational RFC, thus it might be less stable than
[122]2122    this specification. On the other hand, this downward reference was
[277]2123    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2124    therefore it is unlikely to cause problems in practice. See also
2125    <xref target="BCP97"/>.
[122]2126  </annotation>
[131]2129<reference anchor="RFC2045">
2130  <front>
2131    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2132    <author initials="N." surname="Freed" fullname="Ned Freed">
2133      <organization>Innosoft International, Inc.</organization>
2134      <address><email></email></address>
2135    </author>
2136    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2137      <organization>First Virtual Holdings</organization>
2138      <address><email></email></address>
2139    </author>
2140    <date month="November" year="1996"/>
2141  </front>
2142  <seriesInfo name="RFC" value="2045"/>
2145<reference anchor="RFC2046">
2146  <front>
2147    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2148    <author initials="N." surname="Freed" fullname="Ned Freed">
2149      <organization>Innosoft International, Inc.</organization>
2150      <address><email></email></address>
2151    </author>
2152    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2153      <organization>First Virtual Holdings</organization>
2154      <address><email></email></address>
2155    </author>
2156    <date month="November" year="1996"/>
2157  </front>
2158  <seriesInfo name="RFC" value="2046"/>
[119]2161<reference anchor="RFC2119">
2162  <front>
2163    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2164    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2165      <organization>Harvard University</organization>
2166      <address><email></email></address>
2167    </author>
2168    <date month="March" year="1997"/>
2169  </front>
2170  <seriesInfo name="BCP" value="14"/>
2171  <seriesInfo name="RFC" value="2119"/>
[303]2174<reference anchor='RFC4647'>
2175  <front>
2176    <title>Matching of Language Tags</title>
2177    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role="editor">
2178      <organization>Yahoo! Inc.</organization>
2179      <address><email></email></address>
2180    </author>
2181    <author initials='M.' surname='Davis' fullname='Mark Davis' role="editor">
2182      <organization>Google</organization>
2183      <address><email></email></address>
2184    </author>
2185    <date year='2006' month='September' />
2186  </front>
2187  <seriesInfo name='BCP' value='47' />
2188  <seriesInfo name='RFC' value='4647' />
[425]2191<reference anchor="RFC5234">
2192  <front>
2193    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2194    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2195      <organization>Brandenburg InternetWorking</organization>
2196      <address>
[728]2197        <email></email>
2198      </address> 
[425]2199    </author>
2200    <author initials="P." surname="Overell" fullname="Paul Overell">
2201      <organization>THUS plc.</organization>
2202      <address>
[728]2203        <email></email>
2204      </address>
[425]2205    </author>
2206    <date month="January" year="2008"/>
2207  </front>
2208  <seriesInfo name="STD" value="68"/>
2209  <seriesInfo name="RFC" value="5234"/>
[690]2212<reference anchor='RFC5646'>
[613]2213  <front>
2214    <title>Tags for Identifying Languages</title>
2215    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role='editor'>
2216      <organization>Lab126</organization>
2217      <address><email></email></address>
2218    </author>
2219    <author initials='M.' surname='Davis' fullname='Mark Davis' role='editor'>
2220      <organization>Google</organization>
2221      <address><email></email></address>
2222    </author>
[690]2223    <date month='September' year='2009' />
[613]2224  </front>
[690]2225  <seriesInfo name='BCP' value='47' />
2226  <seriesInfo name='RFC' value='5646' />
2231<references title="Informative References">
[129]2233<reference anchor="RFC1945">
2234  <front>
2235    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2236    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2237      <organization>MIT, Laboratory for Computer Science</organization>
2238      <address><email></email></address>
2239    </author>
2240    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2241      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2242      <address><email></email></address>
2243    </author>
2244    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2245      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2246      <address><email></email></address>
2247    </author>
2248    <date month="May" year="1996"/>
2249  </front>
2250  <seriesInfo name="RFC" value="1945"/>
2253<reference anchor="RFC2049">
2254  <front>
2255    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2256    <author initials="N." surname="Freed" fullname="Ned Freed">
2257      <organization>Innosoft International, Inc.</organization>
2258      <address><email></email></address>
2259    </author>
2260    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2261      <organization>First Virtual Holdings</organization>
2262      <address><email></email></address>
2263    </author>
2264    <date month="November" year="1996"/>
2265  </front>
2266  <seriesInfo name="RFC" value="2049"/>
[133]2269<reference anchor="RFC2068">
2270  <front>
2271    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2272    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2273      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2274      <address><email></email></address>
2275    </author>
2276    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2277      <organization>MIT Laboratory for Computer Science</organization>
2278      <address><email></email></address>
2279    </author>
2280    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2281      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2282      <address><email></email></address>
2283    </author>
2284    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2285      <organization>MIT Laboratory for Computer Science</organization>
2286      <address><email></email></address>
2287    </author>
2288    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2289      <organization>MIT Laboratory for Computer Science</organization>
2290      <address><email></email></address>
2291    </author>
2292    <date month="January" year="1997"/>
2293  </front>
2294  <seriesInfo name="RFC" value="2068"/>
[129]2297<reference anchor="RFC2076">
2298  <front>
2299    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2300    <author initials="J." surname="Palme" fullname="Jacob Palme">
2301      <organization>Stockholm University/KTH</organization>
2302      <address><email></email></address>
2303    </author>
2304    <date month="February" year="1997"/>
2305  </front>
2306  <seriesInfo name="RFC" value="2076"/>
2309<reference anchor="RFC2183">
2310  <front>
2311    <title abbrev="Content-Disposition">Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field</title>
2312    <author initials="R." surname="Troost" fullname="Rens Troost">
2313      <organization>New Century Systems</organization>
2314      <address><email></email></address>
2315    </author>
2316    <author initials="S." surname="Dorner" fullname="Steve Dorner">
2317      <organization>QUALCOMM Incorporated</organization>
2318      <address><email></email></address>
2319    </author>
2320    <author initials="K." surname="Moore" fullname="Keith Moore">
2321      <organization>Department of Computer Science</organization>
2322      <address><email></email></address>
2323    </author>
2324    <date month="August" year="1997"/>
2325  </front>
2326  <seriesInfo name="RFC" value="2183"/>
2329<reference anchor="RFC2277">
2330  <front>
2331    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2332    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2333      <organization>UNINETT</organization>
2334      <address><email></email></address>
2335    </author>
2336    <date month="January" year="1998"/>
2337  </front>
2338  <seriesInfo name="BCP" value="18"/>
2339  <seriesInfo name="RFC" value="2277"/>
[745]2342<reference anchor='RFC2295'>
2343  <front>
2344    <title abbrev='HTTP Content Negotiation'>Transparent Content Negotiation in HTTP</title>
2345    <author initials='K.' surname='Holtman' fullname='Koen Holtman'>
2346      <organization>Technische Universiteit Eindhoven</organization>
2347      <address>
2348        <email></email>
2349      </address>
2350    </author>
2351    <author initials='A.H.' surname='Mutz' fullname='Andrew H. Mutz'>
2352      <organization>Hewlett-Packard Company</organization>
2353      <address>
2354        <email></email>
2355      </address>
2356    </author>
2357    <date year='1998' month='March'/>
2358  </front>
2359  <seriesInfo name='RFC' value='2295'/>
[129]2362<reference anchor="RFC2388">
2363  <front>
2364    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2365    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2366      <organization>Xerox Palo Alto Research Center</organization>
2367      <address><email></email></address>
2368    </author>
2369    <date year="1998" month="August"/>
2370  </front>
2371  <seriesInfo name="RFC" value="2388"/>
2374<reference anchor="RFC2557">
2375  <front>
2376    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2377    <author initials="F." surname="Palme" fullname="Jacob Palme">
2378      <organization>Stockholm University and KTH</organization>
2379      <address><email></email></address>
2380    </author>
2381    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2382      <organization>Microsoft Corporation</organization>
2383      <address><email></email></address>
2384    </author>
2385    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2386      <organization>Lotus Development Corporation</organization>
2387      <address><email></email></address>
2388    </author>
2389    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2390      <address><email></email></address>
2391    </author>
2392    <date year="1999" month="March"/>
2393  </front>
2394  <seriesInfo name="RFC" value="2557"/>
[119]2397<reference anchor="RFC2616">
2398  <front>
2399    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2400    <author initials="R." surname="Fielding" fullname="R. Fielding">
2401      <organization>University of California, Irvine</organization>
2402      <address><email></email></address>
2403    </author>
2404    <author initials="J." surname="Gettys" fullname="J. Gettys">
2405      <organization>W3C</organization>
2406      <address><email></email></address>
2407    </author>
2408    <author initials="J." surname="Mogul" fullname="J. Mogul">
2409      <organization>Compaq Computer Corporation</organization>
2410      <address><email></email></address>
2411    </author>
2412    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2413      <organization>MIT Laboratory for Computer Science</organization>
2414      <address><email></email></address>
2415    </author>
2416    <author initials="L." surname="Masinter" fullname="L. Masinter">
2417      <organization>Xerox Corporation</organization>
2418      <address><email></email></address>
2419    </author>
2420    <author initials="P." surname="Leach" fullname="P. Leach">
2421      <organization>Microsoft Corporation</organization>
2422      <address><email></email></address>
2423    </author>
2424    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2425      <organization>W3C</organization>
2426      <address><email></email></address>
2427    </author>
2428    <date month="June" year="1999"/>
2429  </front>
2430  <seriesInfo name="RFC" value="2616"/>
[129]2433<reference anchor="RFC3629">
2434  <front>
2435    <title>UTF-8, a transformation format of ISO 10646</title>
2436    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2437      <organization>Alis Technologies</organization>
2438      <address><email></email></address>
2439    </author>
2440    <date month="November" year="2003"/>
2441  </front>
2442  <seriesInfo name="RFC" value="3629"/>
2443  <seriesInfo name="STD" value="63"/>
[253]2446<reference anchor='RFC3864'>
2447  <front>
2448    <title>Registration Procedures for Message Header Fields</title>
2449    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2450      <organization>Nine by Nine</organization>
2451      <address><email></email></address>
2452    </author>
2453    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2454      <organization>BEA Systems</organization>
2455      <address><email></email></address>
2456    </author>
2457    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2458      <organization>HP Labs</organization>
2459      <address><email></email></address>
2460    </author>
2461    <date year='2004' month='September' />
2462  </front>
2463  <seriesInfo name='BCP' value='90' />
2464  <seriesInfo name='RFC' value='3864' />
[200]2467<reference anchor="RFC4288">
2468  <front>
2469    <title>Media Type Specifications and Registration Procedures</title>
2470    <author initials="N." surname="Freed" fullname="N. Freed">
2471      <organization>Sun Microsystems</organization>
2472      <address>
2473        <email></email>
2474      </address>
2475    </author>
2476    <author initials="J." surname="Klensin" fullname="J. Klensin">
2477      <address>
2478        <email></email>
2479      </address>
2480    </author>
2481    <date year="2005" month="December"/>
2482  </front>
2483  <seriesInfo name="BCP" value="13"/>
2484  <seriesInfo name="RFC" value="4288"/>
[670]2487<reference anchor='RFC5226'>
2488  <front>
2489    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2490    <author initials='T.' surname='Narten' fullname='T. Narten'>
2491      <organization>IBM</organization>
2492      <address><email></email></address>
2493    </author>
2494    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
2495      <organization>Google</organization>
2496      <address><email></email></address>
2497    </author>
2498    <date year='2008' month='May' />
2499  </front>
2500  <seriesInfo name='BCP' value='26' />
2501  <seriesInfo name='RFC' value='5226' />
[327]2504<reference anchor="RFC5322">
2505  <front>
2506    <title>Internet Message Format</title>
2507    <author initials="P." surname="Resnick" fullname="P. Resnick">
2508      <organization>Qualcomm Incorporated</organization>
2509    </author>
2510    <date year="2008" month="October"/>
2511  </front>
2512  <seriesInfo name="RFC" value="5322"/>
[277]2515<reference anchor='BCP97'>
2516  <front>
2517    <title>Handling Normative References to Standards-Track Documents</title>
2518    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
2519      <address>
2520        <email></email>
2521      </address>
2522    </author>
2523    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
2524      <organization>MIT</organization>
2525      <address>
2526        <email></email>
2527      </address>
2528    </author>
2529    <date year='2007' month='June' />
2530  </front>
2531  <seriesInfo name='BCP' value='97' />
2532  <seriesInfo name='RFC' value='4897' />
[874]2538<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
[327]2540   HTTP/1.1 uses many of the constructs defined for Internet Mail (<xref target="RFC5322"/>) and the Multipurpose Internet Mail Extensions (MIME <xref target="RFC2045"/>) to
[874]2541   allow a message-body to be transmitted in an open variety of
[8]2542   representations and with extensible mechanisms. However, RFC 2045
2543   discusses mail, and HTTP has a few features that are different from
[874]2544   those described in MIME. These differences were carefully chosen
[8]2545   to optimize performance over binary connections, to allow greater
2546   freedom in the use of new media types, to make date comparisons
2547   easier, and to acknowledge the practice of some early HTTP servers
2548   and clients.
[874]2551   This appendix describes specific areas where HTTP differs from MIME.
2552   Proxies and gateways to strict MIME environments &SHOULD; be
[8]2553   aware of these differences and provide the appropriate conversions
2554   where necessary. Proxies and gateways from MIME environments to HTTP
2555   also need to be aware of the differences because some conversions
2556   might be required.
[8]2559<section title="MIME-Version" anchor="mime-version">
[291]2560  <iref primary="true" item="MIME-Version header" x:for-anchor=""/>
2561  <iref primary="true" item="Headers" subitem="MIME-Version" x:for-anchor=""/>
[229]2562  <x:anchor-alias value="MIME-Version"/>
[357]2563  <x:anchor-alias value="MIME-Version-v"/>
2565   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages &MAY;
2566   include a single MIME-Version general-header field to indicate what
2567   version of the MIME protocol was used to construct the message. Use
2568   of the MIME-Version header field indicates that the message is in
[115]2569   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
[8]2570   Proxies/gateways are responsible for ensuring full compliance (where
2571   possible) when exporting HTTP messages to strict MIME environments.
[357]2573<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/>
[366]2574  <x:ref>MIME-Version</x:ref>   = "MIME-Version" ":" <x:ref>OWS</x:ref> <x:ref>MIME-Version-v</x:ref>
[357]2575  <x:ref>MIME-Version-v</x:ref> = 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
2578   MIME version "1.0" is the default for use in HTTP/1.1. However,
2579   HTTP/1.1 message parsing and semantics are defined by this document
2580   and not the MIME specification.
2584<section title="Conversion to Canonical Form" anchor="">
[874]2586   MIME requires that an Internet mail body-part be converted to
[115]2587   canonical form prior to being transferred, as described in <xref target="RFC2049" x:fmt="of" x:sec="4"/>.
[97]2588   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
[8]2589   allowed for subtypes of the "text" media type when transmitted over
[97]2590   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
[8]2591   line breaks as CRLF and forbids the use of CR or LF outside of line
2592   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2593   line break within text content when a message is transmitted over
2594   HTTP.
2597   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2598   environment &SHOULD; translate all line breaks within the text media
2599   types described in <xref target="canonicalization.and.text.defaults"/> of this document to the RFC 2049
2600   canonical form of CRLF. Note, however, that this might be complicated
2601   by the presence of a Content-Encoding and by the fact that HTTP
2602   allows the use of some character sets which do not use octets 13 and
2603   10 to represent CR and LF, as is the case for some multi-byte
2604   character sets.
[969]2607   Conversion will break any cryptographic
[8]2608   checksums applied to the original content unless the original content
2609   is already in canonical form. Therefore, the canonical form is
2610   recommended for any content that uses such checksums in HTTP.
2615<section title="Conversion of Date Formats" anchor="">
2617   HTTP/1.1 uses a restricted set of date formats (&full-date;) to
2618   simplify the process of date comparison. Proxies and gateways from
2619   other protocols &SHOULD; ensure that any Date header field present in a
2620   message conforms to one of the HTTP/1.1 formats and rewrite the date
2621   if necessary.
[8]2625<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
[874]2627   MIME does not include any concept equivalent to HTTP/1.1's
[8]2628   Content-Encoding header field. Since this acts as a modifier on the
2629   media type, proxies and gateways from HTTP to MIME-compliant
2630   protocols &MUST; either change the value of the Content-Type header
[874]2631   field or decode the representation before forwarding the message. (Some
[8]2632   experimental applications of Content-Type for Internet mail have used
2633   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2634   a function equivalent to Content-Encoding. However, this parameter is
[874]2635   not part of the MIME standards).
2639<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
[874]2641   HTTP does not use the Content-Transfer-Encoding field of MIME.
2642   Proxies and gateways from MIME-compliant protocols to HTTP &MUST;
[85]2643   remove any Content-Transfer-Encoding
[8]2644   prior to delivering the response message to an HTTP client.
2647   Proxies and gateways from HTTP to MIME-compliant protocols are
2648   responsible for ensuring that the message is in the correct format
2649   and encoding for safe transport on that protocol, where "safe
2650   transport" is defined by the limitations of the protocol being used.
2651   Such a proxy or gateway &SHOULD; label the data with an appropriate
2652   Content-Transfer-Encoding if doing so will improve the likelihood of
2653   safe transport over the destination protocol.
2657<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
[29]2659   HTTP/1.1 introduces the Transfer-Encoding header field (&header-transfer-encoding;).
[8]2660   Proxies/gateways &MUST; remove any transfer-coding prior to
2661   forwarding a message via a MIME-compliant protocol.
2665<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
[129]2667   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
[8]2668   need to be aware of MIME line length limitations. Since HTTP does not
2669   have this limitation, HTTP does not fold long lines. MHTML messages
2670   being transported by HTTP follow all conventions of MHTML, including
2671   line length limitations and folding, canonicalization, etc., since
2672   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2673   does not interpret the content or any MIME header lines that might be
2674   contained therein.
2679<section title="Additional Features" anchor="additional.features">
[97]2681   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
[8]2682   existing HTTP implementations, but not consistently and correctly
2683   across most HTTP/1.1 applications. Implementors are advised to be
2684   aware of these features, but cannot rely upon their presence in, or
2685   interoperability with, other HTTP/1.1 applications. Some of these
2686   describe proposed experimental features, and some describe features
2687   that experimental deployment found lacking that are now addressed in
2688   the base HTTP/1.1 specification.
2691   A number of other headers, such as Content-Disposition and Title,
[97]2692   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2695<section title="Content-Disposition" anchor="content-disposition">
2696<iref item="Headers" subitem="Content-Disposition" primary="true" x:for-anchor=""/>
2697<iref item="Content-Disposition header" primary="true" x:for-anchor=""/>
[229]2698  <x:anchor-alias value="content-disposition"/>
[357]2699  <x:anchor-alias value="content-disposition-v"/>
[229]2700  <x:anchor-alias value="disposition-type"/>
2701  <x:anchor-alias value="disposition-parm"/>
2702  <x:anchor-alias value="disp-extension-parm"/>
2703  <x:anchor-alias value="disp-extension-token"/>
2704  <x:anchor-alias value="filename-parm"/>
[697]2706   The "Content-Disposition" response-header field has been proposed as a
[8]2707   means for the origin server to suggest a default filename if the user
2708   requests that the content is saved to a file. This usage is derived
[269]2709   from the definition of Content-Disposition in <xref target="RFC2183"/>.
[357]2711<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-disposition"/><iref primary="true" item="Grammar" subitem="content-disposition-v"/><iref primary="true" item="Grammar" subitem="disposition-type"/><iref primary="true" item="Grammar" subitem="disposition-parm"/><iref primary="true" item="Grammar" subitem="filename-parm"/><iref primary="true" item="Grammar" subitem="disp-extension-token"/><iref primary="true" item="Grammar" subitem="disp-extension-parm"/>
[366]2712  <x:ref>content-disposition</x:ref> = "Content-Disposition" ":" <x:ref>OWS</x:ref>
[357]2713                        <x:ref>content-disposition-v</x:ref>
[376]2714  <x:ref>content-disposition-v</x:ref> = <x:ref>disposition-type</x:ref>
2715                          *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>disposition-parm</x:ref> )
[334]2716  <x:ref>disposition-type</x:ref> = "attachment" / <x:ref>disp-extension-token</x:ref>
2717  <x:ref>disposition-parm</x:ref> = <x:ref>filename-parm</x:ref> / <x:ref>disp-extension-parm</x:ref>
[229]2718  <x:ref>filename-parm</x:ref> = "filename" "=" <x:ref>quoted-string</x:ref>
2719  <x:ref>disp-extension-token</x:ref> = <x:ref>token</x:ref>
[810]2720  <x:ref>disp-extension-parm</x:ref> = <x:ref>token</x:ref> "=" <x:ref>word</x:ref>
2723   An example is
2725<figure><artwork type="example">
[458]2726  Content-Disposition: attachment; filename="fname.ext"
2729   The receiving user agent &SHOULD-NOT;  respect any directory path
2730   information present in the filename-parm parameter, which is the only
2731   parameter believed to apply to HTTP implementations at this time. The
2732   filename &SHOULD; be treated as a terminal component only.
2735   If this header is used in a response with the application/octet-stream
2736   content-type, the implied suggestion is that the user agent
[746]2737   should not display the response, but directly enter a "save response
2738   as..." dialog.
2741   See <xref target="content-disposition.issues"/> for Content-Disposition security issues.
[99]2746<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2748  Clarify contexts that charset is used in.
2749  (<xref target="character.sets"/>)
[712]2752  Remove base URI setting semantics for Content-Location due to poor
[714]2753  implementation support, which was caused by too many broken servers emitting
2754  bogus Content-Location headers, and also the potentially undesirable effect
2755  of potentially breaking relative links in content-negotiated resources.
[712]2756  (<xref target="header.content-location"/>)
[104]2759  Remove reference to non-existant identity transfer-coding value tokens.
2760  (<xref target="no.content-transfer-encoding"/>)
[680]2764<?BEGININC p3-payload.abnf-appendix ?>
[427]2765<section xmlns:x="" title="Collected ABNF" anchor="collected.abnf">
2767<artwork type="abnf" name="p3-payload.parsed-abnf">
2768<x:ref>Accept</x:ref> = "Accept:" OWS Accept-v
2769<x:ref>Accept-Charset</x:ref> = "Accept-Charset:" OWS Accept-Charset-v
2770<x:ref>Accept-Charset-v</x:ref> = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
[425]2771 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2772 qvalue ] ] )
[427]2773<x:ref>Accept-Encoding</x:ref> = "Accept-Encoding:" OWS Accept-Encoding-v
2774<x:ref>Accept-Encoding-v</x:ref> = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
[425]2775 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
[427]2776<x:ref>Accept-Language</x:ref> = "Accept-Language:" OWS Accept-Language-v
2777<x:ref>Accept-Language-v</x:ref> = *( "," OWS ) language-range [ OWS ";" OWS "q="
[425]2778 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2779 ] )
[427]2780<x:ref>Accept-v</x:ref> = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
[425]2781 OWS media-range [ accept-params ] ] ) ]
[427]2783<x:ref>Content-Encoding</x:ref> = "Content-Encoding:" OWS Content-Encoding-v
2784<x:ref>Content-Encoding-v</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
[425]2785 content-coding ] )
[427]2786<x:ref>Content-Language</x:ref> = "Content-Language:" OWS Content-Language-v
2787<x:ref>Content-Language-v</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
[425]2788 language-tag ] )
[678]2789<x:ref>Content-Length</x:ref> = &lt;Content-Length, defined in [Part1], Section 9.2&gt;
[427]2790<x:ref>Content-Location</x:ref> = "Content-Location:" OWS Content-Location-v
2791<x:ref>Content-Location-v</x:ref> = absolute-URI / partial-URI
2792<x:ref>Content-MD5</x:ref> = "Content-MD5:" OWS Content-MD5-v
2793<x:ref>Content-MD5-v</x:ref> = &lt;base64 of 128 bit MD5 digest as per [RFC1864]&gt;
2794<x:ref>Content-Range</x:ref> = &lt;Content-Range, defined in [Part5], Section 5.2&gt;
2795<x:ref>Content-Type</x:ref> = "Content-Type:" OWS Content-Type-v
2796<x:ref>Content-Type-v</x:ref> = media-type
[538]2798<x:ref>Expires</x:ref> = &lt;Expires, defined in [Part6], Section 3.3&gt;
2800<x:ref>Last-Modified</x:ref> = &lt;Last-Modified, defined in [Part4], Section 6.6&gt;
2802<x:ref>MIME-Version</x:ref> = "MIME-Version:" OWS MIME-Version-v
2803<x:ref>MIME-Version-v</x:ref> = 1*DIGIT "." 1*DIGIT
2805<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
[648]2807<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
[810]2808<x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" word ]
[427]2809<x:ref>accept-params</x:ref> = OWS ";" OWS "q=" qvalue *accept-ext
2810<x:ref>attribute</x:ref> = token
2812<x:ref>charset</x:ref> = token
2813<x:ref>codings</x:ref> = ( content-coding / "*" )
2814<x:ref>content-coding</x:ref> = token
2815<x:ref>content-disposition</x:ref> = "Content-Disposition:" OWS
[425]2816 content-disposition-v
[427]2817<x:ref>content-disposition-v</x:ref> = disposition-type *( OWS ";" OWS
[425]2818 disposition-parm )
[810]2820<x:ref>disp-extension-parm</x:ref> = token "=" word
[427]2821<x:ref>disp-extension-token</x:ref> = token
2822<x:ref>disposition-parm</x:ref> = filename-parm / disp-extension-parm
2823<x:ref>disposition-type</x:ref> = "attachment" / disp-extension-token
2825<x:ref>filename-parm</x:ref> = "filename=" quoted-string
[678]2827<x:ref>header-field</x:ref> = &lt;header-field, defined in [Part1], Section 3.2&gt;
[427]2829<x:ref>language-range</x:ref> = &lt;language-range, defined in [RFC4647], Section 2.1&gt;
[690]2830<x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in [RFC5646], Section 2.1&gt;
2832<x:ref>media-range</x:ref> = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
[425]2833 ";" OWS parameter )
[427]2834<x:ref>media-type</x:ref> = type "/" subtype *( OWS ";" OWS parameter )
2836<x:ref>parameter</x:ref> = attribute "=" value
[648]2837<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
2839<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
[678]2840<x:ref>qvalue</x:ref> = &lt;qvalue, defined in [Part1], Section 6.4&gt;
2842<x:ref>subtype</x:ref> = token
2844<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
2845<x:ref>type</x:ref> = token
[810]2847<x:ref>value</x:ref> = word
2849<x:ref>word</x:ref> = &lt;word, defined in [Part1], Section 1.2.2&gt;
[532]2852<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
2853; Accept defined but not used
[425]2854; Accept-Charset defined but not used
2855; Accept-Encoding defined but not used
2856; Accept-Language defined but not used
[968]2857; Content-Encoding defined but not used
2858; Content-Language defined but not used
2859; Content-Length defined but not used
2860; Content-Location defined but not used
2861; Content-MD5 defined but not used
2862; Content-Range defined but not used
2863; Content-Type defined but not used
2864; Expires defined but not used
2865; Last-Modified defined but not used
[425]2866; MIME-Version defined but not used
2867; content-disposition defined but not used
[968]2868; header-field defined but not used
[680]2870<?ENDINC p3-payload.abnf-appendix ?>
[252]2872<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2874<section title="Since RFC2616">
2876  Extracted relevant partitions from <xref target="RFC2616"/>.
2880<section title="Since draft-ietf-httpbis-p3-payload-00">
[116]2882  Closed issues:
2883  <list style="symbols">
2884    <t>
[324]2885      <eref target=""/>:
[116]2886      "Media Type Registrations"
2887      (<eref target=""/>)
2888    </t>
2889    <t>
[324]2890      <eref target=""/>:
[116]2891      "Clarification regarding quoting of charset values"
2892      (<eref target=""/>)
2893    </t>
2894    <t>
[324]2895      <eref target=""/>:
[116]2896      "Remove 'identity' token references"
2897      (<eref target=""/>)
2898    </t>
2899    <t>
[324]2900      <eref target=""/>:
[126]2901      "Accept-Encoding BNF"
2902    </t>
2903    <t>
[324]2904      <eref target=""/>:
[152]2905      "Normative and Informative references"
2906    </t>
2907    <t>
[324]2908      <eref target=""/>:
[116]2909      "RFC1700 references"
2910    </t>
[122]2911    <t>
[324]2912      <eref target=""/>:
[200]2913      "Updating to RFC4288"
2914    </t>
2915    <t>
[324]2916      <eref target=""/>:
[129]2917      "Informative references"
2918    </t>
2919    <t>
[324]2920      <eref target=""/>:
[123]2921      "ISO-8859-1 Reference"
2922    </t>
2923    <t>
[324]2924      <eref target=""/>:
[122]2925      "Encoding References Normative"
2926    </t>
[131]2927    <t>
[324]2928      <eref target=""/>:
[131]2929      "Normative up-to-date references"
2930    </t>
[116]2931  </list>
[170]2935<section title="Since draft-ietf-httpbis-p3-payload-01">
[324]2937  Ongoing work on ABNF conversion (<eref target=""/>):
[205]2938  <list style="symbols">
2939    <t>
2940      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2941    </t>
2942  </list>
[252]2946<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
[232]2948  Closed issues:
2949  <list style="symbols">
2950    <t>
[324]2951      <eref target=""/>:
[251]2952      "Quoting Charsets"
2953    </t>
2954    <t>
[324]2955      <eref target=""/>:
[232]2956      "Classification for Allow header"
2957    </t>
[248]2958    <t>
[324]2959      <eref target=""/>:
[248]2960      "missing default for qvalue in description of Accept-Encoding"
2961    </t>
[232]2962  </list>
[324]2965  Ongoing work on IANA Message Header Registration (<eref target=""/>):
[253]2966  <list style="symbols">
2967    <t>
2968      Reference RFC 3984, and update header registrations for headers defined
2969      in this document.
2970    </t>
2971  </list>
[267]2975<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
[269]2977  Closed issues:
2978  <list style="symbols">
2979    <t>
[297]2980      <eref target=""/>:
2981      "Quoting Charsets"
2982    </t>
2983    <t>
[303]2984      <eref target=""/>:
2985      "language tag matching (Accept-Language) vs RFC4647"
2986    </t>
2987    <t>
[277]2988      <eref target=""/>:
[269]2989      "RFC 1806 has been replaced by RFC2183"
2990    </t>
2991  </list>
2994  Other changes:
2995  <list style="symbols">
2996    <t>
2997      <eref target=""/>:
2998      "Encoding References Normative" -- rephrase the annotation and reference
2999      <xref target="BCP97"/>.
3000    </t>
3001  </list>
[269]3003 </section>
[323]3005<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
[327]3007  Closed issues:
3008  <list style="symbols">
3009    <t>
3010      <eref target=""/>:
3011      "RFC 2822 is updated by RFC 5322"
3012    </t>
3013  </list>
3016  Ongoing work on ABNF conversion (<eref target=""/>):
3017  <list style="symbols">
3018    <t>
3019      Use "/" instead of "|" for alternatives.
3020    </t>
[357]3021    <t>
3022      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3023      whitespace ("OWS") and required whitespace ("RWS").
3024    </t>
3025    <t>
3026      Rewrite ABNFs to spell out whitespace rules, factor out
3027      header value format definitions.
3028    </t>
[334]3029  </list>
[382]3033<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
[385]3035  Closed issues:
3036  <list style="symbols">
3037    <t>
3038      <eref target=""/>:
3039      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
3040    </t>
3041  </list>
[543]3044  Final work on ABNF conversion (<eref target=""/>):
[421]3045  <list style="symbols">
3046    <t>
[424]3047      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
[421]3048    </t>
3049  </list>
3052  Other changes:
3053  <list style="symbols">
3054    <t>
3055      Move definition of quality values into Part 1.
3056    </t>
3057  </list>
[547]3061<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
[577]3063  Closed issues:
3064  <list style="symbols">
3065    <t>
3066      <eref target=""/>:
3067      "Content-Location isn't special"
3068    </t>
[592]3069    <t>
3070      <eref target=""/>:
3071      "Content Sniffing"
3072    </t>
[577]3073  </list>
[604]3077<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
[613]3079  Closed issues:
3080  <list style="symbols">
3081    <t>
[670]3082      <eref target=""/>:
[613]3083      "Updated reference for language tags"
3084    </t>
[663]3085    <t>
[716]3086      <eref target=""/>:
3087      "Clarify rules for determining what entities a response carries"
3088    </t>
3089    <t>
[712]3090      <eref target=""/>:
3091      "Content-Location base-setting problems"
3092    </t>
3093    <t>
[663]3094      <eref target=""/>:
3095      "Content Sniffing"
3096    </t>
[670]3097    <t>
3098      <eref target=""/>:
3099      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
3100    </t>
[673]3101    <t>
3102      <eref target=""/>:
3103      "move definitions of gzip/deflate/compress to part 1"
3104    </t>
[613]3105  </list>
3108  Partly resolved issues:
3109  <list style="symbols">
3110    <t>
3111      <eref target=""/>:
3112      "update IANA requirements wrt Transfer-Coding values" (add the
3113      IANA Considerations subsection)
3114    </t>
[668]3115    <t>
3116      <eref target=""/>:
3117      "update IANA requirements wrt Content-Coding values" (add the
3118      IANA Considerations subsection)
3119    </t>
[667]3120  </list>
[720]3124<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
[724]3126  Closed issues:
3127  <list style="symbols">
3128    <t>
[745]3129      <eref target=""/>:
3130      "Content Negotiation for media types"
3131    </t>
3132    <t>
[724]3133      <eref target=""/>:
3134      "Accept-Language: which RFC4647 filtering?"
3135    </t>
3136  </list>
[773]3140<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
[808]3142  Closed issues:
3143  <list style="symbols">
3144    <t>
[937]3145      <eref target=""/>:
3146      "MIME-Version not listed in P1, general header fields"
3147    </t>
3148    <t>
[808]3149      <eref target=""/>:
3150      "IANA registry for content/transfer encodings"
3151    </t>
[810]3152    <t>
[831]3153      <eref target=""/>:
3154      "Content Sniffing"
3155    </t>
3156    <t>
[810]3157      <eref target=""/>:
3158      "use of term "word" when talking about header structure"
3159    </t>
[808]3160  </list>
3163  Partly resolved issues:
3164  <list style="symbols">
3165    <t>
3166      <eref target=""/>:
3167      "Term for the requested resource's URI"
3168    </t>
3169  </list>
[841]3173<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
[854]3175  Closed issues:
3176  <list style="symbols">
3177    <t>
[858]3178      <eref target=""/>:
3179      "Clarify 'Requested Variant'"
3180    </t>
3181    <t>
3182      <eref target=""/>:
3183      "Content-Location isn't special"
3184    </t>
3185    <t>
[854]3186      <eref target=""/>:
3187      "Delimiting messages with multipart/byteranges"
3188    </t>
[858]3189    <t>
3190      <eref target=""/>:
3191      "Clarify entity / representation / variant terminology"
3192    </t>
3193    <t>
3194      <eref target=""/>:
3195      "confusing req. language for Content-Location"
3196    </t>
3197    <t>
3198      <eref target=""/>:
3199      "Content-Location on 304 responses"
3200    </t>
[882]3201    <t>
3202      <eref target=""/>:
3203      "'requested resource' in content-encoding definition"
3204    </t>
[911]3205    <t>
3206      <eref target=""/>:
3207      "consider removing the 'changes from 2068' sections"
3208    </t>
[854]3209  </list>
3212  Partly resolved issues:
3213  <list style="symbols">
3214    <t>
3215      <eref target=""/>:
3216      "Content-MD5 and partial responses"
3217    </t>
3218  </list>
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