source: draft-ietf-httpbis/latest/p3-payload.xml @ 1626

Last change on this file since 1626 was 1604, checked in by julian.reschke@…, 8 years ago

replace a few instances of lowercase "must"

  • Property svn:eol-style set to native
  • Property svn:mime-type set to text/xml
File size: 118.1 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>">
[29]14  <!ENTITY ID-VERSION "latest">
[1552]15  <!ENTITY ID-MONTH "March">
[1497]16  <!ENTITY ID-YEAR "2012">
[1101]17  <!ENTITY mdash "&#8212;">
[1454]18  <!ENTITY architecture             "<xref target='Part1' x:rel='#architecture' xmlns:x=''/>">
[424]19  <!ENTITY notation                 "<xref target='Part1' x:rel='#notation' xmlns:x=''/>">
[1518]20  <!ENTITY abnf-extension           "<xref target='Part1' x:rel='#abnf.extension' xmlns:x=''/>">
[1399]21  <!ENTITY acks                     "<xref target='Part1' x:rel='#acks' xmlns:x=''/>">
[1518]22  <!ENTITY whitespace               "<xref target='Part1' x:rel='#whitespace' xmlns:x=''/>">
23  <!ENTITY field-components         "<xref target='Part1' x:rel='#field.components' xmlns:x=''/>">
[115]24  <!ENTITY caching-neg-resp         "<xref target='Part6' x:rel='#caching.negotiated.responses' xmlns:x=''/>">
[31]25  <!ENTITY header-transfer-encoding "<xref target='Part1' x:rel='#header.transfer-encoding' xmlns:x=''/>">
26  <!ENTITY header-content-length    "<xref target='Part1' x:rel='#header.content-length' xmlns:x=''/>">
27  <!ENTITY header-content-range     "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
[1571]28  <!ENTITY header-etag              "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
[31]29  <!ENTITY header-expires           "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
30  <!ENTITY header-last-modified     "<xref target='Part4' x:rel='#header.last-modified' xmlns:x=''/>">
31  <!ENTITY header-user-agent        "<xref target='Part2' x:rel='#header.user-agent' xmlns:x=''/>">
[115]32  <!ENTITY header-vary              "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
[31]33  <!ENTITY message-body             "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
34  <!ENTITY multipart-byteranges     "<xref target='Part5' x:rel='' xmlns:x=''/>">
[1436]35  <!ENTITY http-date                "<xref target='Part2' x:rel='' xmlns:x=''/>">
[457]36  <!ENTITY qvalue                   "<xref target='Part1' x:rel='#quality.values' xmlns:x=''/>">
[374]37  <!ENTITY uri                      "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
[823]38  <!ENTITY effective-request-uri    "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x=''/>">
[808]39  <!ENTITY compression-codings      "<xref target='Part1' x:rel='#compression.codings' xmlns:x=''/>">
40  <!ENTITY transfer-codings         "<xref target='Part1' x:rel='#transfer.codings' xmlns:x=''/>">
[673]41  <!ENTITY compress-coding          "<xref target='Part1' x:rel='#compress.coding' xmlns:x=''/>">
42  <!ENTITY deflate-coding           "<xref target='Part1' x:rel='#deflate.coding' xmlns:x=''/>">
43  <!ENTITY gzip-coding              "<xref target='Part1' x:rel='#gzip.coding' xmlns:x=''/>">
[716]44  <!ENTITY response-representation  "<xref target='Part2' x:rel='#identifying.response.associated.with.representation' xmlns:x=''/>">
46<?rfc toc="yes" ?>
[29]47<?rfc symrefs="yes" ?>
48<?rfc sortrefs="yes" ?>
[8]49<?rfc compact="yes"?>
50<?rfc subcompact="no" ?>
51<?rfc linkmailto="no" ?>
52<?rfc editing="no" ?>
[203]53<?rfc comments="yes"?>
54<?rfc inline="yes"?>
[799]55<?rfc rfcedstyle="yes"?>
[8]56<?rfc-ext allow-markup-in-artwork="yes" ?>
57<?rfc-ext include-references-in-index="yes" ?>
[1477]58<rfc obsoletes="2616" category="std" x:maturity-level="proposed"
[446]59     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-&ID-VERSION;"
[153]60     xmlns:x=''>
[1472]61<x:link rel="prev" basename="p2-semantics"/>
62<x:link rel="next" basename="p4-conditional"/>
[1522]63<x:feedback template="{docname},%20%22{section}%22&amp;body=&lt;{ref}&gt;:"/>
[120]66  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
[29]68  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]69    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[8]70    <address>
71      <postal>
[1106]72        <street>345 Park Ave</street>
73        <city>San Jose</city>
[8]74        <region>CA</region>
[1106]75        <code>95110</code>
[29]76        <country>USA</country>
[8]77      </postal>
[29]78      <email></email>
79      <uri></uri>
[8]80    </address>
81  </author>
[95]83  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]84    <organization abbrev="W3C">World Wide Web Consortium</organization>
85    <address>
86      <postal>
87        <street>W3C / ERCIM</street>
88        <street>2004, rte des Lucioles</street>
89        <city>Sophia-Antipolis</city>
90        <region>AM</region>
91        <code>06902</code>
92        <country>France</country>
93      </postal>
94      <email></email>
95      <uri></uri>
96    </address>
97  </author>
[95]99  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
100    <organization abbrev="greenbytes">greenbytes GmbH</organization>
101    <address>
102      <postal>
103        <street>Hafenweg 16</street>
104        <city>Muenster</city><region>NW</region><code>48155</code>
105        <country>Germany</country>
106      </postal>
[609]107      <phone>+49 251 2807760</phone>
108      <facsimile>+49 251 2807761</facsimile>
109      <email></email>
110      <uri></uri>
[95]111    </address>
112  </author>
[31]114  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
[440]115  <workgroup>HTTPbis Working Group</workgroup>
[1373]119   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
120   distributed, collaborative, hypertext information systems. HTTP has been in
121   use by the World Wide Web global information initiative since 1990. This
122   document is Part 3 of the seven-part specification that defines the protocol
123   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
126   Part 3 defines HTTP message content, metadata, and content negotiation.
130<note title="Editorial Note (To be removed by RFC Editor)">
131  <t>
132    Discussion of this draft should take place on the HTTPBIS working group
[1268]133    mailing list (, which is archived at
134    <eref target=""/>.
135  </t>
136  <t>
137    The current issues list is at
138    <eref target=""/> and related
139    documents (including fancy diffs) can be found at
[324]140    <eref target=""/>.
[36]141  </t>
[153]142  <t>
[1592]143    The changes in this draft are summarized in <xref target="changes.since.19"/>.
[153]144  </t>
148<section title="Introduction" anchor="introduction">
[163]150   This document defines HTTP/1.1 message payloads (a.k.a., content), the
[161]151   associated metadata header fields that define how the payload is intended
152   to be interpreted by a recipient, the request header fields that
[908]153   might influence content selection, and the various selection algorithms
[161]154   that are collectively referred to as HTTP content negotiation.
157   This document is currently disorganized in order to minimize the changes
158   between drafts and enable reviewers to see the smaller errata changes.
[980]159   A future draft will reorganize the sections to better reflect the content.
[161]160   In particular, the sections on entities will be renamed payload and moved
161   to the first half of the document, while the sections on content negotiation
162   and associated request header fields will be moved to the second half.  The
163   current mess reflects how widely dispersed these topics and associated
164   requirements had become in <xref target="RFC2616"/>.
[660]167<section title="Terminology" anchor="terminology">
169   This specification uses a number of terms to refer to the roles
170   played by participants in, and objects of, the HTTP communication.
173  <iref item="content negotiation"/>
174  <x:dfn>content negotiation</x:dfn>
175  <list>
176    <t>
177      The mechanism for selecting the appropriate representation when
[856]178      servicing a request. The representation in any response
[660]179      can be negotiated (including error responses).
180    </t>
181  </list>
184  <iref primary="true" item="selected representation"/>
185  <x:dfn>selected representation</x:dfn>
186  <list>
187    <t>
188      The current representation of the target resource that would have been
189      selected in a successful response if the same request had used the
190      method GET and excluded any conditional request header fields.
191    </t>
192  </list>
[1452]196<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
198   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
199   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
200   document are to be interpreted as described in <xref target="RFC2119"/>.
[1452]203   This document defines conformance criteria for several roles in HTTP
204   communication, including Senders, Recipients, Clients, Servers, User-Agents,
205   Origin Servers, Intermediaries, Proxies and Gateways. See &architecture;
206   for definitions of these terms.
209   An implementation is considered conformant if it complies with all of the
210   requirements associated with its role(s). Note that SHOULD-level requirements
211   are relevant here, unless one of the documented exceptions is applicable.
214   This document also uses ABNF to define valid protocol elements
215   (<xref target="notation"/>). In addition to the prose requirements placed
216   upon them, Senders &MUST-NOT; generate protocol elements that are invalid.
219   Unless noted otherwise, Recipients &MAY; take steps to recover a usable
220   protocol element from an invalid construct. However, HTTP does not define
221   specific error handling mechanisms, except in cases where it has direct
222   impact on security. This is because different uses of the protocol require
223   different error handling strategies; for example, a Web browser may wish to
224   transparently recover from a response where the Location header field
225   doesn't parse according to the ABNF, whereby in a systems control protocol
226   using HTTP, this type of error recovery could lead to dangerous consequences.
[424]230<section title="Syntax Notation" anchor="notation">
[425]231  <x:anchor-alias value="ALPHA"/>
232  <x:anchor-alias value="CR"/>
233  <x:anchor-alias value="DIGIT"/>
234  <x:anchor-alias value="LF"/>
235  <x:anchor-alias value="OCTET"/>
236  <x:anchor-alias value="VCHAR"/>
[1518]238   This specification uses the Augmented Backus-Naur Form (ABNF) notation
239   of <xref target="RFC5234"/> with the list rule extension defined in
240   &notation;.  <xref target="collected.abnf"/> shows the collected ABNF
241   with the list rule expanded.
[425]244  The following core rules are included by
245  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
246  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
247  DIGIT (decimal 0-9), DQUOTE (double quote),
248  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
[1425]249  OCTET (any 8-bit sequence of data), SP (space), and
250  VCHAR (any visible US-ASCII character).
253<section title="Core Rules" anchor="core.rules">
[229]254  <x:anchor-alias value="token"/>
[810]255  <x:anchor-alias value="word"/>
[357]256  <x:anchor-alias value="OWS"/>
[1396]258  The core rules below are defined in <xref target="Part1"/>:
260<figure><artwork type="abnf2616">
[1518]261  <x:ref>OWS</x:ref>            = &lt;OWS, defined in &whitespace;&gt;
262  <x:ref>token</x:ref>          = &lt;token, defined in &field-components;&gt;
263  <x:ref>word</x:ref>           = &lt;word, defined in &field-components;&gt;
267<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]268  <x:anchor-alias value="absolute-URI"/>
[391]269  <x:anchor-alias value="partial-URI"/>
[457]270  <x:anchor-alias value="qvalue"/>
[206]272  The ABNF rules below are defined in other parts:
[207]274<figure><!--Part1--><artwork type="abnf2616">
[374]275  <x:ref>absolute-URI</x:ref>   = &lt;absolute-URI, defined in &uri;&gt;
[391]276  <x:ref>partial-URI</x:ref>    = &lt;partial-URI, defined in &uri;&gt;
[457]277  <x:ref>qvalue</x:ref>         = &lt;qvalue, defined in &qvalue;&gt;
[8]285<section title="Protocol Parameters" anchor="protocol.parameters">
[1176]287<section title="Character Encodings (charset)" anchor="character.sets">
[1176]289   HTTP uses charset names to indicate the character encoding of a
290   textual representation.
[229]292<t anchor="rule.charset">
293  <x:anchor-alias value="charset"/>
[1176]294   A character encoding is identified by a case-insensitive token. The
[8]295   complete set of tokens is defined by the IANA Character Set registry
[91]296   (<eref target=""/>).
298<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="charset"/>
[229]299  <x:ref>charset</x:ref> = <x:ref>token</x:ref>
302   Although HTTP allows an arbitrary token to be used as a charset
303   value, any token that has a predefined value within the IANA
[1176]304   Character Set registry &MUST; represent the character encoding defined
[8]305   by that registry. Applications &SHOULD; limit their use of character
[1176]306   encodings to those defined within the IANA registry.
[81]309   HTTP uses charset in two contexts: within an Accept-Charset request
[994]310   header field (in which the charset value is an unquoted token) and as the
311   value of a parameter in a Content-Type header field (within a request or
[81]312   response), in which case the parameter value of the charset parameter
[908]313   can be quoted.
[969]316   Implementors need to be aware of IETF character set requirements <xref target="RFC3629"/>
[8]317   <xref target="RFC2277"/>.
321<section title="Content Codings" anchor="content.codings">
[229]322  <x:anchor-alias value="content-coding"/>
324   Content coding values indicate an encoding transformation that has
[866]325   been or can be applied to a representation. Content codings are primarily
326   used to allow a representation to be compressed or otherwise usefully
[8]327   transformed without losing the identity of its underlying media type
[866]328   and without loss of information. Frequently, the representation is stored in
[8]329   coded form, transmitted directly, and only decoded by the recipient.
331<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-coding"/>
[229]332  <x:ref>content-coding</x:ref>   = <x:ref>token</x:ref>
335   All content-coding values are case-insensitive. HTTP/1.1 uses
336   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
337   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
338   describes the content-coding, what is more important is that it
339   indicates what decoding mechanism will be required to remove the
340   encoding.
[673]343   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
344  <list>
345    <t>
346      See &compress-coding;.
347    </t>
348  </list>
[673]351   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
[8]352  <list>
353    <t>
[673]354      See &deflate-coding;.
[8]355    </t>
356  </list>
[673]359   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
360  <list>
361    <t>
362      See &gzip-coding;.
363    </t>
364  </list>
367<section title="Content Coding Registry" anchor="content.coding.registry">
[670]369   The HTTP Content Coding Registry defines the name space for the content
370   coding names.
373   Registrations &MUST; include the following fields:
374   <list style="symbols">
375     <t>Name</t>
376     <t>Description</t>
377     <t>Pointer to specification text</t>
378   </list>
[808]381   Names of content codings &MUST-NOT; overlap with names of transfer codings
[1514]382   (&transfer-codings;), unless the encoding transformation is identical (as
[808]383   is the case for the compression codings defined in
384   &compression-codings;).
[1567]387   Values to be added to this name space require IETF Review
388   (see <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
[8]389   conform to the purpose of content coding defined in this section.
392   The registry itself is maintained at
393   <eref target=""/>.
[8]399<section title="Media Types" anchor="media.types">
[229]400  <x:anchor-alias value="media-type"/>
401  <x:anchor-alias value="type"/>
402  <x:anchor-alias value="subtype"/>
[152]404   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
[8]405   and Accept (<xref target="header.accept"/>) header fields in order to provide
406   open and extensible data typing and type negotiation.
408<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]409  <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> )
410  <x:ref>type</x:ref>       = <x:ref>token</x:ref>
411  <x:ref>subtype</x:ref>    = <x:ref>token</x:ref>
[229]413<t anchor="rule.parameter">
414  <x:anchor-alias value="attribute"/>
415  <x:anchor-alias value="parameter"/>
416  <x:anchor-alias value="value"/>
[1153]417   The type/subtype &MAY; be followed by parameters in the form of
418   attribute/value pairs.
[29]420<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]421  <x:ref>parameter</x:ref>      = <x:ref>attribute</x:ref> "=" <x:ref>value</x:ref>
422  <x:ref>attribute</x:ref>      = <x:ref>token</x:ref>
[810]423  <x:ref>value</x:ref>          = <x:ref>word</x:ref>
426   The type, subtype, and parameter attribute names are case-insensitive.
[370]427   Parameter values might or might not be case-sensitive, depending on the
428   semantics of the parameter name.  The presence or absence of a parameter might
[8]429   be significant to the processing of a media-type, depending on its
430   definition within the media type registry.
[908]433   A parameter value that matches the <x:ref>token</x:ref> production can be
[297]434   transmitted as either a token or within a quoted-string. The quoted and
435   unquoted values are equivalent.
[8]438   Note that some older HTTP applications do not recognize media type
439   parameters. When sending data to older HTTP applications,
440   implementations &SHOULD; only use media type parameters when they are
441   required by that type/subtype definition.
444   Media-type values are registered with the Internet Assigned Number
[91]445   Authority (IANA). The media type registration process is
[115]446   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
[8]447   discouraged.
450<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
[874]452   Internet media types are registered with a canonical form. A
453   representation transferred via HTTP messages &MUST; be in the
[8]454   appropriate canonical form prior to its transmission except for
455   "text" types, as defined in the next paragraph.
458   When in canonical form, media subtypes of the "text" type use CRLF as
459   the text line break. HTTP relaxes this requirement and allows the
460   transport of text media with plain CR or LF alone representing a line
[874]461   break when it is done consistently for an entire representation. HTTP
462   applications &MUST; accept CRLF, bare CR, and bare LF as indicating
463   a line break in text media received via HTTP. In
464   addition, if the text is in a character encoding that does not
[8]465   use octets 13 and 10 for CR and LF respectively, as is the case for
[874]466   some multi-byte character encodings, HTTP allows the use of whatever octet
467   sequences are defined by that character encoding to represent the
[8]468   equivalent of CR and LF for line breaks. This flexibility regarding
[874]469   line breaks applies only to text media in the payload body; a bare CR
[8]470   or LF &MUST-NOT; be substituted for CRLF within any of the HTTP control
471   structures (such as header fields and multipart boundaries).
[874]474   If a representation is encoded with a content-coding, the underlying
[8]475   data &MUST; be in a form defined above prior to being encoded.
479<section title="Multipart Types" anchor="multipart.types">
[1101]481   MIME provides for a number of "multipart" types &mdash; encapsulations of
[1544]482   one or more representations within a single message body. All multipart
[97]483   types share a common syntax, as defined in <xref target="RFC2046" x:sec="5.1.1" x:fmt="of"/>,
484   and &MUST; include a boundary parameter as part of the media type
[8]485   value. The message body is itself a protocol element and &MUST;
486   therefore use only CRLF to represent line breaks between body-parts.
[1544]489   In general, HTTP treats a multipart message body no differently than
[852]490   any other media type: strictly as payload.  HTTP does not use the
[1544]491   multipart boundary as an indicator of message body length.
[97]492   <!-- jre: re-insert removed text pointing to caching? -->
[852]493   In all other respects, an HTTP user agent &SHOULD; follow the same or similar
[8]494   behavior as a MIME user agent would upon receipt of a multipart type.
[1544]495   The MIME header fields within each body-part of a multipart message body
[8]496   do not have any significance to HTTP beyond that defined by
497   their MIME semantics.
500   If an application receives an unrecognized multipart subtype, the
501   application &MUST; treat it as being equivalent to "multipart/mixed".
504  <t>
505    <x:h>Note:</x:h> The "multipart/form-data" type has been specifically defined
506    for carrying form data suitable for processing via the POST
507    request method, as described in <xref target="RFC2388"/>.
508  </t>
513<section title="Language Tags" anchor="language.tags">
[229]514  <x:anchor-alias value="language-tag"/>
[690]516   A language tag, as defined in <xref target="RFC5646"/>, identifies a
[613]517   natural language spoken, written, or otherwise conveyed by human beings for
518   communication of information to other human beings. Computer languages are
519   explicitly excluded. HTTP uses language tags within the Accept-Language and
520   Content-Language fields.
[613]523   In summary, a language tag is composed of one or more parts: A primary
524   language subtag followed by a possibly empty series of subtags:
[613]526<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="language-tag"/>
[690]527  <x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in <xref target="RFC5646" x:sec="2.1"/>&gt;
530   White space is not allowed within the tag and all tags are case-insensitive.
[613]531   The name space of language subtags is administered by the IANA (see
532   <eref target=""/>).
535  <preamble>Example tags include:</preamble>
536<artwork type="example">
537  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
[690]541   See <xref target="RFC5646"/> for further information.
[965]546<section title="Payload" anchor="payload">
[965]548   HTTP messages &MAY; transfer a payload if not otherwise restricted by
549   the request method or response status code.  The payload consists of
550   metadata, in the form of header fields, and data, in the form of the
[1544]551   sequence of octets in the message body after any transfer-coding has
[965]552   been decoded.
[965]554<iref item="payload"/>
556   A "<x:dfn>payload</x:dfn>" in HTTP is always a partial or complete
557   representation of some resource.  We use separate terms for payload
558   and representation because some messages contain only the associated
559   representation's header fields (e.g., responses to HEAD) or only some
560   part(s) of the representation (e.g., the 206 status code).
562<section title="Payload Header Fields" anchor="payload.header.fields">
563  <x:anchor-alias value="payload-header"/>
[965]565   HTTP header fields that specifically define the payload, rather than the
566   associated representation, are referred to as "payload header fields".
567   The following payload header fields are defined by HTTP/1.1:
[1138]569<texttable align="left">
570  <ttcol>Header Field Name</ttcol>
571  <ttcol>Defined in...</ttcol>
573  <c>Content-Length</c> <c>&header-content-length;</c>
574  <c>Content-Range</c> <c>&header-content-range;</c>
[874]578<section title="Payload Body" anchor="payload.body">
579  <x:anchor-alias value="payload-body"/>
[1544]581   A payload body is only present in a message when a message body is
[874]582   present, as described in &message-body;. The payload body is obtained
[1544]583   from the message body by decoding any Transfer-Encoding that might
[8]584   have been applied to ensure safe and proper transfer of the message.
[965]589<section title="Representation" anchor="representation">
590<iref item="representation"/>
[965]592   A "<x:dfn>representation</x:dfn>" is information in a format that can be readily
593   communicated from one party to another.  A resource representation
594   is information that reflects the state of that resource, as observed
595   at some point in the past (e.g., in a response to GET) or to be
596   desired at some point in the future (e.g., in a PUT request).
599   Most, but not all, representations transferred via HTTP are intended
600   to be a representation of the target resource (the resource identified
601   by the effective request URI).  The precise semantics of a representation
602   are determined by the type of message (request or response), the request
603   method, the response status code, and the representation metadata.
604   For example, the above semantic is true for the representation in any
605   200 (OK) response to GET and for the representation in any PUT request.
606   A 200 response to PUT, in contrast, contains either a representation
607   that describes the successful action or a representation of the target
608   resource, with the latter indicated by a Content-Location header field
609   with the same value as the effective request URI.  Likewise, response
610   messages with an error status code usually contain a representation that
611   describes the error and what next steps are suggested for resolving it.
614<section title="Representation Header Fields" anchor="representation.header.fields">
615  <x:anchor-alias value="representation-header"/>
617   Representation header fields define metadata about the representation data
[1544]618   enclosed in the message body or, if no message body is present, about
[965]619   the representation that would have been transferred in a 200 response
620   to a simultaneous GET request with the same effective request URI.
623   The following header fields are defined as representation metadata:
[1138]625<texttable align="left">
626  <ttcol>Header Field Name</ttcol>
627  <ttcol>Defined in...</ttcol>
629  <c>Content-Encoding</c> <c><xref target="header.content-encoding"/></c>
630  <c>Content-Language</c> <c><xref target="header.content-language"/></c>
631  <c>Content-Location</c> <c><xref target="header.content-location"/></c>
632  <c>Content-Type</c> <c><xref target="header.content-type"/></c>
633  <c>Expires</c> <c>&header-expires;</c>
636   Additional header fields define metadata about the selected
637   representation, which might differ from the representation included
638   in the message for responses to some state-changing methods.
639   The following header fields are defined as selected representation
640   metadata:
642<texttable align="left">
643  <ttcol>Header Field Name</ttcol>
644  <ttcol>Defined in...</ttcol>
646  <c>ETag</c> <c>&header-etag;</c>
[1138]647  <c>Last-Modified</c> <c>&header-last-modified;</c>
651<section title="Representation Data" anchor="">
652  <x:anchor-alias value="representation-data"/>
654   The representation body associated with an HTTP message is
655   either provided as the payload body of the message or
656   referred to by the message semantics and the effective request
657   URI.  The representation data is in a format and encoding defined by
658   the representation metadata header fields.
661   The data type of the representation data
662   is determined via the header fields Content-Type and Content-Encoding.
[8]663   These define a two-layer, ordered encoding model:
665<figure><artwork type="example">
[965]666  representation-data := Content-Encoding( Content-Type( bits ) )
[965]669   Content-Type specifies the media type of the underlying data, which
670   defines both the data format and how that data &SHOULD; be processed
671   by the recipient (within the scope of the request method semantics).
672   Any HTTP/1.1 message containing a payload body &SHOULD; include a
673   Content-Type header field defining the media type of the associated
674   representation unless that metadata is unknown to the sender.
[831]675   If the Content-Type header field is not present, it indicates that
[965]676   the sender does not know the media type of the representation;
677   recipients &MAY; either assume that the media type is
678   "application/octet-stream" (<xref target="RFC2046" x:fmt="," x:sec="4.5.1"/>)
[592]679   or examine the content to determine its type.
[965]682   In practice, resource owners do not always properly configure their origin
683   server to provide the correct Content-Type for a given representation,
684   with the result that some clients will examine a response body's content
685   and override the specified type.
[908]686   Clients that do so risk drawing incorrect conclusions, which might expose
[965]687   additional security risks (e.g., "privilege escalation").  Furthermore,
688   it is impossible to determine the sender's intent by examining the data
689   format: many data formats match multiple media types that differ only in
690   processing semantics.  Implementers are encouraged to provide a means of
691   disabling such "content sniffing" when it is used.
[908]694   Content-Encoding is used to indicate any additional content
[8]695   codings applied to the data, usually for the purpose of data
[965]696   compression, that are a property of the representation.  If
697   Content-Encoding is not present, then there is no additional
698   encoding beyond that defined by the Content-Type.
703<section title="Content Negotiation" anchor="content.negotiation">
[745]705   HTTP responses include a representation which contains information for
706   interpretation, whether by a human user or for further processing.
707   Often, the server has different ways of representing the
708   same information; for example, in different formats, languages,
709   or using different character encodings.
[745]712   HTTP clients and their users might have different or variable
713   capabilities, characteristics or preferences which would influence
714   which representation, among those available from the server,
715   would be best for the server to deliver. For this reason, HTTP
[1101]716   provides mechanisms for "content negotiation" &mdash; a process of
[745]717   allowing selection of a representation of a given resource,
718   when more than one is available.
[745]721   This specification defines two patterns of content negotiation;
722   "server-driven", where the server selects the representation based
723   upon the client's stated preferences, and "agent-driven" negotiation,
724   where the server provides a list of representations for the client to
725   choose from, based upon their metadata. In addition,  there are
726   other patterns: some applications use an "active content" pattern,
727   where the server returns active content which runs on the client
728   and, based on client available parameters, selects additional
729   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
730   has also been proposed.
733   These patterns are all widely used, and have trade-offs in applicability
734   and practicality. In particular, when the number of preferences or
735   capabilities to be expressed by a client are large (such as when many
736   different formats are supported by a user-agent), server-driven
[908]737   negotiation becomes unwieldy, and might not be appropriate. Conversely,
[745]738   when the number of representations to choose from is very large,
[908]739   agent-driven negotiation might not be appropriate.
742   Note that in all cases, the supplier of representations has the
743   responsibility for determining which representations might be
744   considered to be the "same information".
747<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
749   If the selection of the best representation for a response is made by
750   an algorithm located at the server, it is called server-driven
751   negotiation. Selection is based on the available representations of
[763]752   the response (the dimensions over which it can vary; e.g., language,
[8]753   content-coding, etc.) and the contents of particular header fields in
754   the request message or on other information pertaining to the request
755   (such as the network address of the client).
758   Server-driven negotiation is advantageous when the algorithm for
759   selecting from among the available representations is difficult to
760   describe to the user agent, or when the server desires to send its
761   "best guess" to the client along with the first response (hoping to
762   avoid the round-trip delay of a subsequent request if the "best
763   guess" is good enough for the user). In order to improve the server's
764   guess, the user agent &MAY; include request header fields (Accept,
765   Accept-Language, Accept-Encoding, etc.) which describe its
766   preferences for such a response.
769   Server-driven negotiation has disadvantages:
770  <list style="numbers">
771    <t>
772         It is impossible for the server to accurately determine what
773         might be "best" for any given user, since that would require
774         complete knowledge of both the capabilities of the user agent
775         and the intended use for the response (e.g., does the user want
776         to view it on screen or print it on paper?).
777    </t>
778    <t>
779         Having the user agent describe its capabilities in every
780         request can be both very inefficient (given that only a small
781         percentage of responses have multiple representations) and a
782         potential violation of the user's privacy.
783    </t>
784    <t>
785         It complicates the implementation of an origin server and the
786         algorithms for generating responses to a request.
787    </t>
788    <t>
[908]789         It might limit a public cache's ability to use the same response
[8]790         for multiple user's requests.
791    </t>
792  </list>
[1335]795   Server-driven negotiation allows the user agent to specify its preferences,
[1514]796   but it cannot expect responses to always honor them. For example, the origin
[1335]797   server might not implement server-driven negotiation, or it might decide that
798   sending a response that doesn't conform to them is better than sending a 406
799   (Not Acceptable) response.
802   Many of the mechanisms for expressing preferences use quality values to
803   declare relative preference. See &qvalue; for more information.
[1163]806   HTTP/1.1 includes the following header fields for enabling
[8]807   server-driven negotiation through description of user agent
808   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
809   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
[745]810   (<xref target="header.accept-language"/>), and User-Agent (&header-user-agent;).
811   However, an origin server is not limited to these dimensions and &MAY; vary
[1163]812   the response based on any aspect of the request, including aspects
813   of the connection (e.g., IP address) or information within extension
814   header fields not defined by this specification.
817  <t>
818    <x:h>Note:</x:h> In practice, User-Agent based negotiation is fragile,
819    because new clients might not be recognized.
820  </t>
[115]823   The Vary header field (&header-vary;) can be used to express the parameters the
[8]824   server uses to select a representation that is subject to server-driven
[29]825   negotiation.
829<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
831   With agent-driven negotiation, selection of the best representation
832   for a response is performed by the user agent after receiving an
833   initial response from the origin server. Selection is based on a list
834   of the available representations of the response included within the
[874]835   header fields or body of the initial response, with each
[8]836   representation identified by its own URI. Selection from among the
[908]837   representations can be performed automatically (if the user agent is
[8]838   capable of doing so) or manually by the user selecting from a
839   generated (possibly hypertext) menu.
842   Agent-driven negotiation is advantageous when the response would vary
843   over commonly-used dimensions (such as type, language, or encoding),
844   when the origin server is unable to determine a user agent's
845   capabilities from examining the request, and generally when public
846   caches are used to distribute server load and reduce network usage.
849   Agent-driven negotiation suffers from the disadvantage of needing a
850   second request to obtain the best alternate representation. This
851   second request is only efficient when caching is used. In addition,
852   this specification does not define any mechanism for supporting
853   automatic selection, though it also does not prevent any such
854   mechanism from being developed as an extension and used within
855   HTTP/1.1.
[745]858   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
[8]859   status codes for enabling agent-driven negotiation when the server is
860   unwilling or unable to provide a varying response using server-driven
861   negotiation.
[1415]866<section title="Header Field Definitions" anchor="header.field.definitions">
[117]868   This section defines the syntax and semantics of HTTP/1.1 header fields
869   related to the payload of messages.
[8]872<section title="Accept" anchor="header.accept">
[1120]873  <iref primary="true" item="Accept header field" x:for-anchor=""/>
874  <iref primary="true" item="Header Fields" subitem="Accept" x:for-anchor=""/>
[229]875  <x:anchor-alias value="Accept"/>
[370]876  <x:anchor-alias value="accept-ext"/>
[229]877  <x:anchor-alias value="accept-params"/>
878  <x:anchor-alias value="media-range"/>
[1163]880   The "Accept" header field can be used by user agents to specify
[994]881   response media types that are acceptable. Accept header fields can be used to
[698]882   indicate that the request is specifically limited to a small set of desired
883   types, as in the case of a request for an in-line image.
[1234]885<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/>
886  <x:ref>Accept</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
[229]888  <x:ref>media-range</x:ref>    = ( "*/*"
[334]889                   / ( <x:ref>type</x:ref> "/" "*" )
890                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
[370]891                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
892  <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> )
[1039]893  <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref> [ "=" <x:ref>word</x:ref> ]
896   The asterisk "*" character is used to group media types into ranges,
897   with "*/*" indicating all media types and "type/*" indicating all
898   subtypes of that type. The media-range &MAY; include media type
899   parameters that are applicable to that range.
902   Each media-range &MAY; be followed by one or more accept-params,
903   beginning with the "q" parameter for indicating a relative quality
904   factor. The first "q" parameter (if any) separates the media-range
905   parameter(s) from the accept-params. Quality factors allow the user
906   or user agent to indicate the relative degree of preference for that
[457]907   media-range, using the qvalue scale from 0 to 1 (&qvalue;). The
[8]908   default value is q=1.
911  <t>
912    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
913    parameters from Accept extension parameters is due to historical
914    practice. Although this prevents any media type parameter named
915    "q" from being used with a media range, such an event is believed
916    to be unlikely given the lack of any "q" parameters in the IANA
917    media type registry and the rare usage of any media type
918    parameters in Accept. Future media types are discouraged from
919    registering any parameter named "q".
920  </t>
923   The example
925<figure><artwork type="example">
[357]926  Accept: audio/*; q=0.2, audio/basic
929   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
[879]930   type if it is the best available after an 80% mark-down in quality".
[1406]933   A request without any Accept header field implies that the user agent
934   will accept any media type in response.
935   If an Accept header field is present in a request and none of the
936   available representations for the response have a media type that is
937   listed as acceptable, the origin server &MAY; either
938   honor the Accept header field by sending a 406 (Not Acceptable) response
939   or disregard the Accept header field by treating the response as if
940   it is not subject to content negotiation.
943   A more elaborate example is
945<figure><artwork type="example">
[357]946  Accept: text/plain; q=0.5, text/html,
947          text/x-dvi; q=0.8, text/x-c
950   Verbally, this would be interpreted as "text/html and text/x-c are
951   the preferred media types, but if they do not exist, then send the
[866]952   text/x-dvi representation, and if that does not exist, send the text/plain
[879]953   representation".
956   Media ranges can be overridden by more specific media ranges or
957   specific media types. If more than one media range applies to a given
958   type, the most specific reference has precedence. For example,
960<figure><artwork type="example">
[1244]961  Accept: text/*, text/plain, text/plain;format=flowed, */*
964   have the following precedence:
[459]965   <list style="numbers">
[1244]966    <t>text/plain;format=flowed</t>
967    <t>text/plain</t>
[459]968    <t>text/*</t>
969    <t>*/*</t>
970   </list>
973   The media type quality factor associated with a given type is
974   determined by finding the media range with the highest precedence
975   which matches that type. For example,
977<figure><artwork type="example">
[357]978  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
979          text/html;level=2;q=0.4, */*;q=0.5
982   would cause the following values to be associated:
[459]984<texttable align="left">
985  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
986  <c>text/html;level=1</c>    <c>1</c>
987  <c>text/html</c>            <c>0.7</c>
988  <c>text/plain</c>           <c>0.3</c>
989  <c>image/jpeg</c>           <c>0.5</c>
990  <c>text/html;level=2</c>    <c>0.4</c>
991  <c>text/html;level=3</c>    <c>0.7</c>
994      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
995      values for certain media ranges. However, unless the user agent is
996      a closed system which cannot interact with other rendering agents,
997      this default set ought to be configurable by the user.
1001<section title="Accept-Charset" anchor="header.accept-charset">
[1120]1002  <iref primary="true" item="Accept-Charset header field" x:for-anchor=""/>
1003  <iref primary="true" item="Header Fields" subitem="Accept-Charset" x:for-anchor=""/>
[229]1004  <x:anchor-alias value="Accept-Charset"/>
[1163]1006   The "Accept-Charset" header field can be used by user agents to
[1176]1007   indicate what character encodings are acceptable in a response
1008   payload. This field allows
[8]1009   clients capable of understanding more comprehensive or special-purpose
[1176]1010   character encodings to signal that capability to a server which is capable of
1011   representing documents in those character encodings.
[1234]1013<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/>
1014  <x:ref>Accept-Charset</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
[376]1015                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[1176]1018   Character encoding values (a.k.a., charsets) are described in
1019   <xref target="character.sets"/>. Each charset &MAY; be given an
1020   associated quality value which represents the user's preference
1021   for that charset. The default value is q=1. An example is
1023<figure><artwork type="example">
[357]1024  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1027   The special value "*", if present in the Accept-Charset field,
[1240]1028   matches every character encoding which is not mentioned elsewhere in the
1029   Accept-Charset field. If no "*" is present in an Accept-Charset field, then
1030   all character encodings not explicitly mentioned get a quality value of 0.
[1406]1033   A request without any Accept-Charset header field implies that the user
1034   agent will accept any character encoding in response.
1035   If an Accept-Charset header field is present in a request and none of the
1036   available representations for the response have a character encoding that
1037   is listed as acceptable, the origin server &MAY; either honor the
1038   Accept-Charset header field by sending a 406 (Not Acceptable) response or
1039   disregard the Accept-Charset header field by treating the response as if
1040   it is not subject to content negotiation.
1044<section title="Accept-Encoding" anchor="header.accept-encoding">
[1120]1045  <iref primary="true" item="Accept-Encoding header field" x:for-anchor=""/>
1046  <iref primary="true" item="Header Fields" subitem="Accept-Encoding" x:for-anchor=""/>
[229]1047  <x:anchor-alias value="Accept-Encoding"/>
1048  <x:anchor-alias value="codings"/>
[1163]1050   The "Accept-Encoding" header field can be used by user agents to
[698]1051   indicate what response content-codings (<xref target="content.codings"/>)
[1406]1052   are acceptable in the response.  An "identity" token is used as a synonym
1053   for "no encoding" in order to communicate when no encoding is preferred.
[1234]1055<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="codings"/>
1056  <x:ref>Accept-Encoding</x:ref>  = #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[1423]1057  <x:ref>codings</x:ref>          = <x:ref>content-coding</x:ref> / "identity" / "*"
[248]1060   Each codings value &MAY; be given an associated quality value which
1061   represents the preference for that encoding. The default value is q=1.
[1406]1064   For example,
1066<figure><artwork type="example">
[357]1067  Accept-Encoding: compress, gzip
1068  Accept-Encoding:
1069  Accept-Encoding: *
1070  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1071  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
[1406]1074   A server tests whether a content-coding for a given representation is
1075   acceptable, according to an Accept-Encoding field, using these rules:
[8]1076  <list style="numbers">
1077      <t>The special "*" symbol in an Accept-Encoding field matches any
1078         available content-coding not explicitly listed in the header
1079         field.</t>
[1406]1081      <t>If the representation has no content-coding, then it is acceptable
1082         by default unless specifically excluded by the Accept-Encoding field
1083         stating either "identity;q=0" or "*;q=0" without a more specific
1084         entry for "identity".</t>
1086      <t>If the representation's content-coding is one of the content-codings
1087         listed in the Accept-Encoding field, then it is acceptable unless
1088         it is accompanied by a qvalue of 0. (As defined in &qvalue;, a
1089         qvalue of 0 means "not acceptable".)</t>
[8]1091      <t>If multiple content-codings are acceptable, then the acceptable
1092         content-coding with the highest non-zero qvalue is preferred.</t>
1093  </list>
[1406]1096   An Accept-Encoding header field with a combined field-value that is empty
1097   implies that the user agent does not want any content-coding in response.
1098   If an Accept-Encoding header field is present in a request and none of the
1099   available representations for the response have a content-coding that
1100   is listed as acceptable, the origin server &SHOULD; send a response
1101   without any content-coding.
[1406]1104   A request without an Accept-Encoding header field implies that the user
1105   agent will accept any content-coding in response, but a representation
1106   without content-coding is preferred for compatibility with the widest
1107   variety of user agents.
1110  <t>
1111    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
1112    associated with content-codings. This means that qvalues will not
1113    work and are not permitted with x-gzip or x-compress.
1114  </t>
1118<section title="Accept-Language" anchor="header.accept-language">
[1120]1119  <iref primary="true" item="Accept-Language header field" x:for-anchor=""/>
1120  <iref primary="true" item="Header Fields" subitem="Accept-Language" x:for-anchor=""/>
[229]1121  <x:anchor-alias value="Accept-Language"/>
1122  <x:anchor-alias value="language-range"/>
[1163]1124   The "Accept-Language" header field can be used by user agents to
[698]1125   indicate the set of natural languages that are preferred in the response.
1126   Language tags are defined in <xref target="language.tags"/>.
[1234]1128<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="language-range"/>
1129  <x:ref>Accept-Language</x:ref> =
[370]1130                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[1234]1131  <x:ref>language-range</x:ref>  =
[303]1132            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
[303]1135   Each language-range can be given an associated quality value which
[8]1136   represents an estimate of the user's preference for the languages
1137   specified by that range. The quality value defaults to "q=1". For
1138   example,
1140<figure><artwork type="example">
[357]1141  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1144   would mean: "I prefer Danish, but will accept British English and
[879]1145   other types of English".
[724]1146   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
[724]1149   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
1150   several matching schemes. Implementations can offer the most appropriate
1151   matching scheme for their requirements.
1154  <t>
[756]1155    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
[724]1156    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
1157    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
[563]1158  </t>
1161   It might be contrary to the privacy expectations of the user to send
[994]1162   an Accept-Language header field with the complete linguistic preferences of
[8]1163   the user in every request. For a discussion of this issue, see
[994]1164   <xref target=""/>.
1167   As intelligibility is highly dependent on the individual user, it is
1168   recommended that client applications make the choice of linguistic
1169   preference available to the user. If the choice is not made
1170   available, then the Accept-Language header field &MUST-NOT; be given in
1171   the request.
1174  <t>
1175    <x:h>Note:</x:h> When making the choice of linguistic preference available to
1176    the user, we remind implementors of  the fact that users are not
1177    familiar with the details of language matching as described above,
[969]1178    and ought to be provided appropriate guidance. As an example, users
[563]1179    might assume that on selecting "en-gb", they will be served any
1180    kind of English document if British English is not available. A
1181    user agent might suggest in such a case to add "en" to get the
1182    best matching behavior.
1183  </t>
1187<section title="Content-Encoding" anchor="header.content-encoding">
[1120]1188  <iref primary="true" item="Content-Encoding header field" x:for-anchor=""/>
1189  <iref primary="true" item="Header Fields" subitem="Content-Encoding" x:for-anchor=""/>
[229]1190  <x:anchor-alias value="Content-Encoding"/>
[965]1192   The "Content-Encoding" header field indicates what content-codings
[1406]1193   have been applied to the representation beyond those inherent in the media
[1604]1194   type, and thus what decoding mechanisms have to be applied in order to obtain
[1406]1195   the media-type referenced by the Content-Type header field.
1196   Content-Encoding is primarily used to allow a representation to be
1197   compressed without losing the identity of its underlying media type.
[1234]1199<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/>
1200  <x:ref>Content-Encoding</x:ref> = 1#<x:ref>content-coding</x:ref>
1203   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1205<figure><artwork type="example">
[357]1206  Content-Encoding: gzip
[866]1209   The content-coding is a characteristic of the representation.
1210   Typically, the representation body is stored with this
[8]1211   encoding and is only decoded before rendering or analogous usage.
[1107]1212   However, a transforming proxy &MAY; modify the content-coding if the
[8]1213   new coding is known to be acceptable to the recipient, unless the
1214   "no-transform" cache-control directive is present in the message.
[1406]1217   If the media type includes an inherent encoding, such as a data format
1218   that is always compressed, then that encoding would not be restated as
1219   a Content-Encoding even if it happens to be the same algorithm as one
1220   of the content-codings.  Such a content-coding would only be listed if,
1221   for some bizarre reason, it is applied a second time to form the
1222   representation.  Likewise, an origin server might choose to publish the
1223   same payload data as multiple representations that differ only in whether
1224   the coding is defined as part of Content-Type or Content-Encoding, since
1225   some user agents will behave differently in their handling of each
1226   response (e.g., open a "Save as ..." dialog instead of automatic
1227   decompression and rendering of content).
[1406]1230   A representation that has a content-coding applied to it &MUST; include
1231   a Content-Encoding header field (<xref target="header.content-encoding"/>)
1232   that lists the content-coding(s) applied.
[866]1235   If multiple encodings have been applied to a representation, the content
[8]1236   codings &MUST; be listed in the order in which they were applied.
1237   Additional information about the encoding parameters &MAY; be provided
[866]1238   by other header fields not defined by this specification.
1241   If the content-coding of a representation in a request message is not
1242   acceptable to the origin server, the server &SHOULD; respond with a
1243   status code of 415 (Unsupported Media Type).
1247<section title="Content-Language" anchor="header.content-language">
[1120]1248  <iref primary="true" item="Content-Language header field" x:for-anchor=""/>
1249  <iref primary="true" item="Header Fields" subitem="Content-Language" x:for-anchor=""/>
[229]1250  <x:anchor-alias value="Content-Language"/>
[965]1252   The "Content-Language" header field describes the natural
[866]1253   language(s) of the intended audience for the representation. Note that this might
[874]1254   not be equivalent to all the languages used within the representation.
[1234]1256<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/>
1257  <x:ref>Content-Language</x:ref> = 1#<x:ref>language-tag</x:ref>
1260   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1261   Content-Language is to allow a user to identify and differentiate
[866]1262   representations according to the user's own preferred language. Thus, if the
[8]1263   body content is intended only for a Danish-literate audience, the
1264   appropriate field is
1266<figure><artwork type="example">
[357]1267  Content-Language: da
1270   If no Content-Language is specified, the default is that the content
1271   is intended for all language audiences. This might mean that the
1272   sender does not consider it to be specific to any natural language,
1273   or that the sender does not know for which language it is intended.
1276   Multiple languages &MAY; be listed for content that is intended for
1277   multiple audiences. For example, a rendition of the "Treaty of
[879]1278   Waitangi", presented simultaneously in the original Maori and English
[8]1279   versions, would call for
1281<figure><artwork type="example">
[357]1282  Content-Language: mi, en
[866]1285   However, just because multiple languages are present within a representation
[8]1286   does not mean that it is intended for multiple linguistic audiences.
1287   An example would be a beginner's language primer, such as "A First
[879]1288   Lesson in Latin", which is clearly intended to be used by an
[8]1289   English-literate audience. In this case, the Content-Language would
1290   properly only include "en".
[1101]1293   Content-Language &MAY; be applied to any media type &mdash; it is not
[8]1294   limited to textual documents.
1298<section title="Content-Location" anchor="header.content-location">
[1120]1299  <iref primary="true" item="Content-Location header field" x:for-anchor=""/>
1300  <iref primary="true" item="Header Fields" subitem="Content-Location" x:for-anchor=""/>
[229]1301  <x:anchor-alias value="Content-Location"/>
[856]1303   The "Content-Location" header field supplies a URI that can be used
1304   as a specific identifier for the representation in this message.
1305   In other words, if one were to perform a GET on this URI at the time
1306   of this message's generation, then a 200 response would contain the
1307   same representation that is enclosed as payload in this message.
[1234]1309<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/>
1310  <x:ref>Content-Location</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
[972]1313   The Content-Location value is not a replacement for the effective
[856]1314   Request URI (&effective-request-uri;).  It is representation metadata.
1315   It has the same syntax and semantics as the header field of the same name
[858]1316   defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
[856]1317   However, its appearance in an HTTP message has some special implications
1318   for HTTP recipients.
[856]1321   If Content-Location is included in a response message and its value
[965]1322   is the same as the effective request URI, then the response payload
[1593]1323   &SHOULD; be considered a current representation of that resource.
[856]1324   For a GET or HEAD request, this is the same as the default semantics
1325   when no Content-Location is provided by the server.  For a state-changing
[1161]1326   request like PUT or POST, it implies that the server's response contains
[856]1327   the new representation of that resource, thereby distinguishing it from
1328   representations that might only report about the action (e.g., "It worked!").
1329   This allows authoring applications to update their local copies without
1330   the need for a subsequent GET request.
[856]1333   If Content-Location is included in a response message and its value
[965]1334   differs from the effective request URI, then the origin server is
[856]1335   informing recipients that this representation has its own, presumably
1336   more specific, identifier.  For a GET or HEAD request, this is an
[965]1337   indication that the effective request URI identifies a resource that
[1571]1338   is subject to content negotiation and the selected representation for
[856]1339   this response can also be found at the identified URI.  For other
1340   methods, such a Content-Location indicates that this representation
1341   contains a report on the action's status and the same report is
1342   available (for future access with GET) at the given URI.  For
[1161]1343   example, a purchase transaction made via a POST request might
[856]1344   include a receipt document as the payload of the 200 response;
1345   the Content-Location value provides an identifier for retrieving
1346   a copy of that same receipt in the future.
1349   If Content-Location is included in a request message, then it &MAY;
1350   be interpreted by the origin server as an indication of where the
1351   user agent originally obtained the content of the enclosed
1352   representation (prior to any subsequent modification of the content
1353   by that user agent).  In other words, the user agent is providing
1354   the same representation metadata that it received with the original
1355   representation.  However, such interpretation &MUST-NOT; be used to
1356   alter the semantics of the method requested by the client.  For
1357   example, if a client makes a PUT request on a negotiated resource
1358   and the origin server accepts that PUT (without redirection), then the
1359   new set of values for that resource is expected to be consistent with
1360   the one representation supplied in that PUT; the Content-Location
1361   cannot be used as a form of reverse content selection that
1362   identifies only one of the negotiated representations to be updated.
1363   If the user agent had wanted the latter semantics, it would have applied
1364   the PUT directly to the Content-Location URI.
1367   A Content-Location field received in a request message is transitory
1368   information that &SHOULD-NOT; be saved with other representation
1369   metadata for use in later responses.  The Content-Location's value
1370   might be saved for use in other contexts, such as within source links
1371   or other metadata.
1374   A cache cannot assume that a representation with a Content-Location
[8]1375   different from the URI used to retrieve it can be used to respond to
[856]1376   later requests on that Content-Location URI.
[965]1379   If the Content-Location value is a partial URI, the partial URI is
1380   interpreted relative to the effective request URI.
1384<section title="Content-Type" anchor="header.content-type">
[1120]1385  <iref primary="true" item="Content-Type header field" x:for-anchor=""/>
1386  <iref primary="true" item="Header Fields" subitem="Content-Type" x:for-anchor=""/>
[229]1387  <x:anchor-alias value="Content-Type"/>
[965]1389   The "Content-Type" header field indicates the media type of the
[874]1390   representation. In the case of responses to the HEAD method, the media type is
[698]1391   that which would have been sent had the request been a GET.
[1234]1393<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/>
1394  <x:ref>Content-Type</x:ref> = <x:ref>media-type</x:ref>
1397   Media types are defined in <xref target="media.types"/>. An example of the field is
1399<figure><artwork type="example">
[357]1400  Content-Type: text/html; charset=ISO-8859-4
[965]1403   Further discussion of Content-Type is provided in <xref target=""/>.
[29]1409<section title="IANA Considerations" anchor="IANA.considerations">
[921]1410<section title="Header Field Registration" anchor="header.field.registration">
[969]1412   The Message Header Field Registry located at <eref target=""/> shall be updated
[290]1413   with the permanent registrations below (see <xref target="RFC3864"/>):
[680]1415<?BEGININC p3-payload.iana-headers ?>
[253]1416<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]1417<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]1418   <ttcol>Header Field Name</ttcol>
1419   <ttcol>Protocol</ttcol>
1420   <ttcol>Status</ttcol>
1421   <ttcol>Reference</ttcol>
1423   <c>Accept</c>
1424   <c>http</c>
1425   <c>standard</c>
1426   <c>
1427      <xref target="header.accept"/>
1428   </c>
1429   <c>Accept-Charset</c>
1430   <c>http</c>
1431   <c>standard</c>
1432   <c>
1433      <xref target="header.accept-charset"/>
1434   </c>
1435   <c>Accept-Encoding</c>
1436   <c>http</c>
1437   <c>standard</c>
1438   <c>
1439      <xref target="header.accept-encoding"/>
1440   </c>
1441   <c>Accept-Language</c>
1442   <c>http</c>
1443   <c>standard</c>
1444   <c>
1445      <xref target="header.accept-language"/>
1446   </c>
1447   <c>Content-Encoding</c>
1448   <c>http</c>
1449   <c>standard</c>
1450   <c>
1451      <xref target="header.content-encoding"/>
1452   </c>
1453   <c>Content-Language</c>
1454   <c>http</c>
1455   <c>standard</c>
1456   <c>
1457      <xref target="header.content-language"/>
1458   </c>
1459   <c>Content-Location</c>
1460   <c>http</c>
1461   <c>standard</c>
1462   <c>
1463      <xref target="header.content-location"/>
1464   </c>
1465   <c>Content-Type</c>
1466   <c>http</c>
1467   <c>standard</c>
1468   <c>
1469      <xref target="header.content-type"/>
1470   </c>
[291]1471   <c>MIME-Version</c>
1472   <c>http</c>
[937]1473   <c>standard</c>
[291]1474   <c>
1475      <xref target="mime-version"/>
1476   </c>
[680]1479<?ENDINC p3-payload.iana-headers ?>
[290]1481   The change controller is: "IETF ( - Internet Engineering Task Force".
[668]1485<section title="Content Coding Registry" anchor="content.coding.registration">
1487   The registration procedure for HTTP Content Codings is now defined
[670]1488   by <xref target="content.coding.registry"/> of this document.
1491   The HTTP Content Codings Registry located at <eref target=""/>
[969]1492   shall be updated with the registration below:
1494<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
[670]1495   <ttcol>Name</ttcol>
[668]1496   <ttcol>Description</ttcol>
1497   <ttcol>Reference</ttcol>
1498   <c>compress</c>
1499   <c>UNIX "compress" program method</c>
1500   <c>
[673]1501      &compress-coding;
[668]1502   </c>
1503   <c>deflate</c>
[806]1504   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1505   the "zlib" data format (<xref target="RFC1950"/>)
1506   </c>
[668]1507   <c>
[673]1508      &deflate-coding;
[668]1509   </c>
1510   <c>gzip</c>
1511   <c>Same as GNU zip <xref target="RFC1952"/></c>
1512   <c>
[673]1513      &gzip-coding;
[668]1514   </c>
[1423]1515   <c>identity</c>
1516   <c>reserved (synonym for "no encoding" in Accept-Encoding header field)</c>
1517   <c>
1518      <xref target="header.accept-encoding"/>
1519   </c>
[8]1525<section title="Security Considerations" anchor="security.considerations">
1527   This section is meant to inform application developers, information
1528   providers, and users of the security limitations in HTTP/1.1 as
1529   described by this document. The discussion does not include
1530   definitive solutions to the problems revealed, though it does make
1531   some suggestions for reducing security risks.
[994]1534<section title="Privacy Issues Connected to Accept Header Fields" anchor="">
[1514]1536   Accept header fields can reveal information about the user to all
[994]1537   servers which are accessed. The Accept-Language header field in particular
[8]1538   can reveal information the user would consider to be of a private
1539   nature, because the understanding of particular languages is often
1540   strongly correlated to the membership of a particular ethnic group.
1541   User agents which offer the option to configure the contents of an
[994]1542   Accept-Language header field to be sent in every request are strongly
[8]1543   encouraged to let the configuration process include a message which
1544   makes the user aware of the loss of privacy involved.
1547   An approach that limits the loss of privacy would be for a user agent
[994]1548   to omit the sending of Accept-Language header fields by default, and to ask
1549   the user whether or not to start sending Accept-Language header fields to a
[1163]1550   server if it detects, by looking for any Vary header fields
[8]1551   generated by the server, that such sending could improve the quality
1552   of service.
1555   Elaborate user-customized accept header fields sent in every request,
1556   in particular if these include quality values, can be used by servers
1557   as relatively reliable and long-lived user identifiers. Such user
1558   identifiers would allow content providers to do click-trail tracking,
1559   and would allow collaborating content providers to match cross-server
1560   click-trails or form submissions of individual users. Note that for
1561   many users not behind a proxy, the network address of the host
1562   running the user agent will also serve as a long-lived user
1563   identifier. In environments where proxies are used to enhance
1564   privacy, user agents ought to be conservative in offering accept
1565   header configuration options to end users. As an extreme privacy
[994]1566   measure, proxies could filter the accept header fields in relayed requests.
[8]1567   General purpose user agents which provide a high degree of header
1568   configurability &SHOULD; warn users about the loss of privacy which can
1569   be involved.
[1364]1575<section title="Acknowledgments" anchor="acks">
1577  See &acks;.
[119]1583<references title="Normative References">
[31]1585<reference anchor="Part1">
[119]1586  <front>
1587    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1588    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1589      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1590      <address><email></email></address>
1591    </author>
1592    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1593      <organization abbrev="W3C">World Wide Web Consortium</organization>
1594      <address><email></email></address>
1595    </author>
1596    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1597      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1598      <address><email></email></address>
1599    </author>
1600    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1601  </front>
1602  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1603  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1606<reference anchor="Part2">
[119]1607  <front>
1608    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1609    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1610      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1611      <address><email></email></address>
1612    </author>
1613    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1614      <organization abbrev="W3C">World Wide Web Consortium</organization>
1615      <address><email></email></address>
1616    </author>
1617    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1618      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1619      <address><email></email></address>
1620    </author>
1621    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1622  </front>
1623  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
1624  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
1627<reference anchor="Part4">
[119]1628  <front>
1629    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1630    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1631      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1632      <address><email></email></address>
1633    </author>
1634    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1635      <organization abbrev="W3C">World Wide Web Consortium</organization>
1636      <address><email></email></address>
1637    </author>
1638    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1639      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1640      <address><email></email></address>
1641    </author>
1642    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1643  </front>
1644  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1645  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1648<reference anchor="Part5">
[119]1649  <front>
1650    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1651    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1652      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1653      <address><email></email></address>
1654    </author>
1655    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1656      <organization abbrev="W3C">World Wide Web Consortium</organization>
1657      <address><email></email></address>
1658    </author>
1659    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1660      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1661      <address><email></email></address>
1662    </author>
1663    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1664  </front>
1665  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
1666  <x:source href="p5-range.xml" basename="p5-range"/>
1669<reference anchor="Part6">
[119]1670  <front>
1671    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1672    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]1673      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]1674      <address><email></email></address>
1675    </author>
1676    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1677      <organization abbrev="W3C">World Wide Web Consortium</organization>
1678      <address><email></email></address>
1679    </author>
[601]1680    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
[1440]1681      <organization>Rackspace</organization>
[601]1682      <address><email></email></address>
1683    </author>
[119]1684    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1685      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1686      <address><email></email></address>
1687    </author>
1688    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1689  </front>
1690  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
1691  <x:source href="p6-cache.xml" basename="p6-cache"/>
[122]1694<reference anchor="RFC1950">
1695  <front>
1696    <title>ZLIB Compressed Data Format Specification version 3.3</title>
1697    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1698      <organization>Aladdin Enterprises</organization>
1699      <address><email></email></address>
1700    </author>
[713]1701    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
[122]1702    <date month="May" year="1996"/>
1703  </front>
1704  <seriesInfo name="RFC" value="1950"/>
[1477]1705  <!--<annotation>
[908]1706    RFC 1950 is an Informational RFC, thus it might be less stable than
[122]1707    this specification. On the other hand, this downward reference was
[1414]1708    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
[277]1709    therefore it is unlikely to cause problems in practice. See also
1710    <xref target="BCP97"/>.
[1477]1711  </annotation>-->
[806]1714<reference anchor="RFC1951">
1715  <front>
1716    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
1717    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1718      <organization>Aladdin Enterprises</organization>
1719      <address><email></email></address>
1720    </author>
1721    <date month="May" year="1996"/>
1722  </front>
1723  <seriesInfo name="RFC" value="1951"/>
[1477]1724  <!--<annotation>
[908]1725    RFC 1951 is an Informational RFC, thus it might be less stable than
[806]1726    this specification. On the other hand, this downward reference was
[1414]1727    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
[806]1728    therefore it is unlikely to cause problems in practice. See also
1729    <xref target="BCP97"/>.
[1477]1730  </annotation>-->
[122]1733<reference anchor="RFC1952">
1734  <front>
1735    <title>GZIP file format specification version 4.3</title>
1736    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
1737      <organization>Aladdin Enterprises</organization>
1738      <address><email></email></address>
1739    </author>
1740    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
1741      <address><email></email></address>
1742    </author>
1743    <author initials="M." surname="Adler" fullname="Mark Adler">
1744      <address><email></email></address>
1745    </author>
1746    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
1747      <address><email></email></address>
1748    </author>
1749    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
1750      <address><email></email></address>
1751    </author>
1752    <date month="May" year="1996"/>
1753  </front>
1754  <seriesInfo name="RFC" value="1952"/>
[1477]1755  <!--<annotation>
[908]1756    RFC 1952 is an Informational RFC, thus it might be less stable than
[122]1757    this specification. On the other hand, this downward reference was
[1414]1758    present since the publication of <xref target="RFC2068" x:fmt="none">RFC 2068</xref> in 1997,
[277]1759    therefore it is unlikely to cause problems in practice. See also
1760    <xref target="BCP97"/>.
[1477]1761  </annotation>-->
[131]1764<reference anchor="RFC2045">
1765  <front>
1766    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
1767    <author initials="N." surname="Freed" fullname="Ned Freed">
1768      <organization>Innosoft International, Inc.</organization>
1769      <address><email></email></address>
1770    </author>
1771    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1772      <organization>First Virtual Holdings</organization>
1773      <address><email></email></address>
1774    </author>
1775    <date month="November" year="1996"/>
1776  </front>
1777  <seriesInfo name="RFC" value="2045"/>
1780<reference anchor="RFC2046">
1781  <front>
1782    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
1783    <author initials="N." surname="Freed" fullname="Ned Freed">
1784      <organization>Innosoft International, Inc.</organization>
1785      <address><email></email></address>
1786    </author>
1787    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1788      <organization>First Virtual Holdings</organization>
1789      <address><email></email></address>
1790    </author>
1791    <date month="November" year="1996"/>
1792  </front>
1793  <seriesInfo name="RFC" value="2046"/>
[119]1796<reference anchor="RFC2119">
1797  <front>
1798    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
1799    <author initials="S." surname="Bradner" fullname="Scott Bradner">
1800      <organization>Harvard University</organization>
1801      <address><email></email></address>
1802    </author>
1803    <date month="March" year="1997"/>
1804  </front>
1805  <seriesInfo name="BCP" value="14"/>
1806  <seriesInfo name="RFC" value="2119"/>
[303]1809<reference anchor='RFC4647'>
1810  <front>
1811    <title>Matching of Language Tags</title>
1812    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role="editor">
1813      <organization>Yahoo! Inc.</organization>
1814      <address><email></email></address>
1815    </author>
1816    <author initials='M.' surname='Davis' fullname='Mark Davis' role="editor">
1817      <organization>Google</organization>
1818      <address><email></email></address>
1819    </author>
1820    <date year='2006' month='September' />
1821  </front>
1822  <seriesInfo name='BCP' value='47' />
1823  <seriesInfo name='RFC' value='4647' />
[425]1826<reference anchor="RFC5234">
1827  <front>
1828    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
1829    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
1830      <organization>Brandenburg InternetWorking</organization>
1831      <address>
[728]1832        <email></email>
1833      </address> 
[425]1834    </author>
1835    <author initials="P." surname="Overell" fullname="Paul Overell">
1836      <organization>THUS plc.</organization>
1837      <address>
[728]1838        <email></email>
1839      </address>
[425]1840    </author>
1841    <date month="January" year="2008"/>
1842  </front>
1843  <seriesInfo name="STD" value="68"/>
1844  <seriesInfo name="RFC" value="5234"/>
[690]1847<reference anchor='RFC5646'>
[613]1848  <front>
1849    <title>Tags for Identifying Languages</title>
1850    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role='editor'>
1851      <organization>Lab126</organization>
1852      <address><email></email></address>
1853    </author>
1854    <author initials='M.' surname='Davis' fullname='Mark Davis' role='editor'>
1855      <organization>Google</organization>
1856      <address><email></email></address>
1857    </author>
[690]1858    <date month='September' year='2009' />
[613]1859  </front>
[690]1860  <seriesInfo name='BCP' value='47' />
1861  <seriesInfo name='RFC' value='5646' />
1866<references title="Informative References">
[129]1868<reference anchor="RFC1945">
1869  <front>
1870    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
1871    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1872      <organization>MIT, Laboratory for Computer Science</organization>
1873      <address><email></email></address>
1874    </author>
1875    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
1876      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
1877      <address><email></email></address>
1878    </author>
1879    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
1880      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
1881      <address><email></email></address>
1882    </author>
1883    <date month="May" year="1996"/>
1884  </front>
1885  <seriesInfo name="RFC" value="1945"/>
1888<reference anchor="RFC2049">
1889  <front>
1890    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
1891    <author initials="N." surname="Freed" fullname="Ned Freed">
1892      <organization>Innosoft International, Inc.</organization>
1893      <address><email></email></address>
1894    </author>
1895    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
1896      <organization>First Virtual Holdings</organization>
1897      <address><email></email></address>
1898    </author>
1899    <date month="November" year="1996"/>
1900  </front>
1901  <seriesInfo name="RFC" value="2049"/>
[133]1904<reference anchor="RFC2068">
1905  <front>
1906    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
1907    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
1908      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
1909      <address><email></email></address>
1910    </author>
1911    <author initials="J." surname="Gettys" fullname="Jim Gettys">
1912      <organization>MIT Laboratory for Computer Science</organization>
1913      <address><email></email></address>
1914    </author>
1915    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1916      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
1917      <address><email></email></address>
1918    </author>
1919    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
1920      <organization>MIT Laboratory for Computer Science</organization>
1921      <address><email></email></address>
1922    </author>
1923    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1924      <organization>MIT Laboratory for Computer Science</organization>
1925      <address><email></email></address>
1926    </author>
1927    <date month="January" year="1997"/>
1928  </front>
1929  <seriesInfo name="RFC" value="2068"/>
[129]1932<reference anchor="RFC2076">
1933  <front>
1934    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
1935    <author initials="J." surname="Palme" fullname="Jacob Palme">
1936      <organization>Stockholm University/KTH</organization>
1937      <address><email></email></address>
1938    </author>
1939    <date month="February" year="1997"/>
1940  </front>
1941  <seriesInfo name="RFC" value="2076"/>
1944<reference anchor="RFC2277">
1945  <front>
1946    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
1947    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
1948      <organization>UNINETT</organization>
1949      <address><email></email></address>
1950    </author>
1951    <date month="January" year="1998"/>
1952  </front>
1953  <seriesInfo name="BCP" value="18"/>
1954  <seriesInfo name="RFC" value="2277"/>
[745]1957<reference anchor='RFC2295'>
1958  <front>
1959    <title abbrev='HTTP Content Negotiation'>Transparent Content Negotiation in HTTP</title>
1960    <author initials='K.' surname='Holtman' fullname='Koen Holtman'>
1961      <organization>Technische Universiteit Eindhoven</organization>
1962      <address>
1963        <email></email>
1964      </address>
1965    </author>
1966    <author initials='A.H.' surname='Mutz' fullname='Andrew H. Mutz'>
1967      <organization>Hewlett-Packard Company</organization>
1968      <address>
1969        <email></email>
1970      </address>
1971    </author>
1972    <date year='1998' month='March'/>
1973  </front>
1974  <seriesInfo name='RFC' value='2295'/>
[129]1977<reference anchor="RFC2388">
1978  <front>
1979    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
1980    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1981      <organization>Xerox Palo Alto Research Center</organization>
1982      <address><email></email></address>
1983    </author>
1984    <date year="1998" month="August"/>
1985  </front>
1986  <seriesInfo name="RFC" value="2388"/>
1989<reference anchor="RFC2557">
1990  <front>
1991    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
1992    <author initials="F." surname="Palme" fullname="Jacob Palme">
1993      <organization>Stockholm University and KTH</organization>
1994      <address><email></email></address>
1995    </author>
1996    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
1997      <organization>Microsoft Corporation</organization>
1998      <address><email></email></address>
1999    </author>
2000    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2001      <organization>Lotus Development Corporation</organization>
2002      <address><email></email></address>
2003    </author>
2004    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2005      <address><email></email></address>
2006    </author>
2007    <date year="1999" month="March"/>
2008  </front>
2009  <seriesInfo name="RFC" value="2557"/>
[119]2012<reference anchor="RFC2616">
2013  <front>
2014    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2015    <author initials="R." surname="Fielding" fullname="R. Fielding">
2016      <organization>University of California, Irvine</organization>
2017      <address><email></email></address>
2018    </author>
2019    <author initials="J." surname="Gettys" fullname="J. Gettys">
2020      <organization>W3C</organization>
2021      <address><email></email></address>
2022    </author>
2023    <author initials="J." surname="Mogul" fullname="J. Mogul">
2024      <organization>Compaq Computer Corporation</organization>
2025      <address><email></email></address>
2026    </author>
2027    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2028      <organization>MIT Laboratory for Computer Science</organization>
2029      <address><email></email></address>
2030    </author>
2031    <author initials="L." surname="Masinter" fullname="L. Masinter">
2032      <organization>Xerox Corporation</organization>
2033      <address><email></email></address>
2034    </author>
2035    <author initials="P." surname="Leach" fullname="P. Leach">
2036      <organization>Microsoft Corporation</organization>
2037      <address><email></email></address>
2038    </author>
2039    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2040      <organization>W3C</organization>
2041      <address><email></email></address>
2042    </author>
2043    <date month="June" year="1999"/>
2044  </front>
2045  <seriesInfo name="RFC" value="2616"/>
[129]2048<reference anchor="RFC3629">
2049  <front>
2050    <title>UTF-8, a transformation format of ISO 10646</title>
2051    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2052      <organization>Alis Technologies</organization>
2053      <address><email></email></address>
2054    </author>
2055    <date month="November" year="2003"/>
2056  </front>
[1003]2057  <seriesInfo name="STD" value="63"/>
[129]2058  <seriesInfo name="RFC" value="3629"/>
[253]2061<reference anchor='RFC3864'>
2062  <front>
2063    <title>Registration Procedures for Message Header Fields</title>
2064    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2065      <organization>Nine by Nine</organization>
2066      <address><email></email></address>
2067    </author>
2068    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2069      <organization>BEA Systems</organization>
2070      <address><email></email></address>
2071    </author>
2072    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2073      <organization>HP Labs</organization>
2074      <address><email></email></address>
2075    </author>
2076    <date year='2004' month='September' />
2077  </front>
2078  <seriesInfo name='BCP' value='90' />
2079  <seriesInfo name='RFC' value='3864' />
[200]2082<reference anchor="RFC4288">
2083  <front>
2084    <title>Media Type Specifications and Registration Procedures</title>
2085    <author initials="N." surname="Freed" fullname="N. Freed">
2086      <organization>Sun Microsystems</organization>
2087      <address>
2088        <email></email>
2089      </address>
2090    </author>
2091    <author initials="J." surname="Klensin" fullname="J. Klensin">
2092      <address>
2093        <email></email>
2094      </address>
2095    </author>
2096    <date year="2005" month="December"/>
2097  </front>
2098  <seriesInfo name="BCP" value="13"/>
2099  <seriesInfo name="RFC" value="4288"/>
[670]2102<reference anchor='RFC5226'>
2103  <front>
2104    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2105    <author initials='T.' surname='Narten' fullname='T. Narten'>
2106      <organization>IBM</organization>
2107      <address><email></email></address>
2108    </author>
2109    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
2110      <organization>Google</organization>
2111      <address><email></email></address>
2112    </author>
2113    <date year='2008' month='May' />
2114  </front>
2115  <seriesInfo name='BCP' value='26' />
2116  <seriesInfo name='RFC' value='5226' />
[327]2119<reference anchor="RFC5322">
2120  <front>
2121    <title>Internet Message Format</title>
2122    <author initials="P." surname="Resnick" fullname="P. Resnick">
2123      <organization>Qualcomm Incorporated</organization>
2124    </author>
2125    <date year="2008" month="October"/>
2126  </front>
2127  <seriesInfo name="RFC" value="5322"/>
[1267]2130<reference anchor="RFC6151">
2131  <front>
2132    <title>Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms</title>
2133    <author initials="S." surname="Turner" fullname="S. Turner"/>
2134    <author initials="L." surname="Chen" fullname="L. Chen"/>
2135    <date year="2011" month="March" />
[1308]2136  </front>
[1267]2137  <seriesInfo name="RFC" value="6151" />
[1477]2140<!--<reference anchor='BCP97'>
[277]2141  <front>
2142    <title>Handling Normative References to Standards-Track Documents</title>
2143    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
2144      <address>
2145        <email></email>
2146      </address>
2147    </author>
2148    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
2149      <organization>MIT</organization>
2150      <address>
2151        <email></email>
2152      </address>
2153    </author>
2154    <date year='2007' month='June' />
2155  </front>
2156  <seriesInfo name='BCP' value='97' />
2157  <seriesInfo name='RFC' value='4897' />
[1307]2160<reference anchor="RFC6266">
[1308]2161  <front>
[1259]2162    <title abbrev="Content-Disposition in HTTP">Use of the Content-Disposition Header Field
2163    in the Hypertext Transfer Protocol (HTTP)</title>
2164    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
2165      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2166      <address>
[1308]2167        <email></email>
[1259]2168      </address>
2169    </author>
[1307]2170    <date month="June" year="2011"/>
[1259]2171  </front>
[1307]2172  <seriesInfo name='RFC' value='6266' />
[874]2177<section title="Differences between HTTP and MIME" anchor="differences.between.http.and.mime">
[327]2179   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
[1544]2180   allow a message body to be transmitted in an open variety of
[8]2181   representations and with extensible mechanisms. However, RFC 2045
2182   discusses mail, and HTTP has a few features that are different from
[874]2183   those described in MIME. These differences were carefully chosen
[8]2184   to optimize performance over binary connections, to allow greater
2185   freedom in the use of new media types, to make date comparisons
2186   easier, and to acknowledge the practice of some early HTTP servers
2187   and clients.
[874]2190   This appendix describes specific areas where HTTP differs from MIME.
2191   Proxies and gateways to strict MIME environments &SHOULD; be
[8]2192   aware of these differences and provide the appropriate conversions
2193   where necessary. Proxies and gateways from MIME environments to HTTP
2194   also need to be aware of the differences because some conversions
2195   might be required.
[8]2198<section title="MIME-Version" anchor="mime-version">
[1120]2199  <iref primary="true" item="MIME-Version header field" x:for-anchor=""/>
2200  <iref primary="true" item="Header Fields" subitem="MIME-Version" x:for-anchor=""/>
[229]2201  <x:anchor-alias value="MIME-Version"/>
2203   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages &MAY;
[1163]2204   include a single MIME-Version header field to indicate what
[8]2205   version of the MIME protocol was used to construct the message. Use
2206   of the MIME-Version header field indicates that the message is in
[1520]2207   full conformance with the MIME protocol (as defined in <xref target="RFC2045"/>).
2208   Proxies/gateways are responsible for ensuring full conformance (where
[8]2209   possible) when exporting HTTP messages to strict MIME environments.
[1234]2211<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="MIME-Version"/>
2212  <x:ref>MIME-Version</x:ref> = 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
2215   MIME version "1.0" is the default for use in HTTP/1.1. However,
2216   HTTP/1.1 message parsing and semantics are defined by this document
2217   and not the MIME specification.
2221<section title="Conversion to Canonical Form" anchor="">
[874]2223   MIME requires that an Internet mail body-part be converted to
[115]2224   canonical form prior to being transferred, as described in <xref target="RFC2049" x:fmt="of" x:sec="4"/>.
[97]2225   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
[8]2226   allowed for subtypes of the "text" media type when transmitted over
[97]2227   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
[8]2228   line breaks as CRLF and forbids the use of CR or LF outside of line
2229   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2230   line break within text content when a message is transmitted over
2231   HTTP.
2234   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2235   environment &SHOULD; translate all line breaks within the text media
[1176]2236   types described in <xref target="canonicalization.and.text.defaults"/>
2237   of this document to the RFC 2049
[8]2238   canonical form of CRLF. Note, however, that this might be complicated
2239   by the presence of a Content-Encoding and by the fact that HTTP
[1176]2240   allows the use of some character encodings which do not use octets 13 and
2241   10 to represent CR and LF, respectively, as is the case for some multi-byte
2242   character encodings.
[969]2245   Conversion will break any cryptographic
[8]2246   checksums applied to the original content unless the original content
2247   is already in canonical form. Therefore, the canonical form is
2248   recommended for any content that uses such checksums in HTTP.
2253<section title="Conversion of Date Formats" anchor="">
[1436]2255   HTTP/1.1 uses a restricted set of date formats (&http-date;) to
[385]2256   simplify the process of date comparison. Proxies and gateways from
2257   other protocols &SHOULD; ensure that any Date header field present in a
2258   message conforms to one of the HTTP/1.1 formats and rewrite the date
2259   if necessary.
[8]2263<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
[874]2265   MIME does not include any concept equivalent to HTTP/1.1's
[8]2266   Content-Encoding header field. Since this acts as a modifier on the
2267   media type, proxies and gateways from HTTP to MIME-compliant
2268   protocols &MUST; either change the value of the Content-Type header
[874]2269   field or decode the representation before forwarding the message. (Some
[8]2270   experimental applications of Content-Type for Internet mail have used
2271   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2272   a function equivalent to Content-Encoding. However, this parameter is
[874]2273   not part of the MIME standards).
2277<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
[1506]2278  <iref item="Content-Transfer-Encoding header field" x:for-anchor=""/>
2279  <iref item="Header Fields" subitem="Content-Transfer-Encoding" x:for-anchor=""/>
[874]2281   HTTP does not use the Content-Transfer-Encoding field of MIME.
2282   Proxies and gateways from MIME-compliant protocols to HTTP &MUST;
[85]2283   remove any Content-Transfer-Encoding
[8]2284   prior to delivering the response message to an HTTP client.
2287   Proxies and gateways from HTTP to MIME-compliant protocols are
2288   responsible for ensuring that the message is in the correct format
2289   and encoding for safe transport on that protocol, where "safe
2290   transport" is defined by the limitations of the protocol being used.
2291   Such a proxy or gateway &SHOULD; label the data with an appropriate
2292   Content-Transfer-Encoding if doing so will improve the likelihood of
2293   safe transport over the destination protocol.
2297<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
[29]2299   HTTP/1.1 introduces the Transfer-Encoding header field (&header-transfer-encoding;).
[8]2300   Proxies/gateways &MUST; remove any transfer-coding prior to
2301   forwarding a message via a MIME-compliant protocol.
2305<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
[129]2307   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
[8]2308   need to be aware of MIME line length limitations. Since HTTP does not
2309   have this limitation, HTTP does not fold long lines. MHTML messages
2310   being transported by HTTP follow all conventions of MHTML, including
2311   line length limitations and folding, canonicalization, etc., since
2312   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2313   does not interpret the content or any MIME header lines that might be
2314   contained therein.
2319<section title="Additional Features" anchor="additional.features">
[97]2321   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
[8]2322   existing HTTP implementations, but not consistently and correctly
2323   across most HTTP/1.1 applications. Implementors are advised to be
2324   aware of these features, but cannot rely upon their presence in, or
2325   interoperability with, other HTTP/1.1 applications. Some of these
2326   describe proposed experimental features, and some describe features
2327   that experimental deployment found lacking that are now addressed in
2328   the base HTTP/1.1 specification.
[994]2331   A number of other header fields, such as Content-Disposition and Title,
[1307]2332   from SMTP and MIME are also often implemented (see <xref target="RFC6266"/>
2333   and <xref target="RFC2076"/>).
[99]2337<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2339  Clarify contexts that charset is used in.
2340  (<xref target="character.sets"/>)
[1567]2343  Registration of Content Codings now requires IETF Review
2344  (<xref target="content.coding.registry"/>)
[1240]2347  Remove the default character encoding for text media types; the default
2348  now is whatever the media type definition says.
2349  (<xref target="canonicalization.and.text.defaults"/>)
[1234]2352  Change ABNF productions for header fields to only define the field value.
[1415]2353  (<xref target="header.field.definitions"/>)
[1308]2356  Remove definition of Content-MD5 header field because it was inconsistently
2357  implemented with respect to partial responses, and also because of known
2358  deficiencies in the hash algorithm itself (see <xref target="RFC6151"/> for details).
[1415]2359  (<xref target="header.field.definitions"/>)
[1240]2362  Remove ISO-8859-1 special-casing in Accept-Charset.
2363  (<xref target="header.accept-charset"/>)
[712]2366  Remove base URI setting semantics for Content-Location due to poor
[714]2367  implementation support, which was caused by too many broken servers emitting
[994]2368  bogus Content-Location header fields, and also the potentially undesirable effect
[714]2369  of potentially breaking relative links in content-negotiated resources.
[712]2370  (<xref target="header.content-location"/>)
[1566]2373  Remove reference to non-existant identity transfer-coding value tokens.
2374  (<xref target="no.content-transfer-encoding"/>)
[1308]2377  Remove discussion of Content-Disposition header field, it is now defined
2378  by <xref target="RFC6266"/>.
[1259]2379  (<xref target="additional.features"/>)
[680]2383<?BEGININC p3-payload.abnf-appendix ?>
[427]2384<section xmlns:x="" title="Collected ABNF" anchor="collected.abnf">
2386<artwork type="abnf" name="p3-payload.parsed-abnf">
[1234]2387<x:ref>Accept</x:ref> = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
2388 OWS media-range [ accept-params ] ] ) ]
2389<x:ref>Accept-Charset</x:ref> = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
[425]2390 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2391 qvalue ] ] )
[1234]2392<x:ref>Accept-Encoding</x:ref> = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] ) )
2393 *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
2394<x:ref>Accept-Language</x:ref> = *( "," OWS ) language-range [ OWS ";" OWS "q="
[425]2395 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2396 ] )
[1234]2398<x:ref>Content-Encoding</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
[425]2399 content-coding ] )
[1234]2400<x:ref>Content-Language</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
[425]2401 language-tag ] )
[1234]2402<x:ref>Content-Location</x:ref> = absolute-URI / partial-URI
2403<x:ref>Content-Type</x:ref> = media-type
[1234]2405<x:ref>MIME-Version</x:ref> = 1*DIGIT "." 1*DIGIT
[1523]2407<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 3.2.1&gt;
[1318]2409<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
[810]2410<x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" word ]
[427]2411<x:ref>accept-params</x:ref> = OWS ";" OWS "q=" qvalue *accept-ext
2412<x:ref>attribute</x:ref> = token
2414<x:ref>charset</x:ref> = token
[1410]2415<x:ref>codings</x:ref> = content-coding / "identity" / "*"
[427]2416<x:ref>content-coding</x:ref> = token
[427]2418<x:ref>language-range</x:ref> = &lt;language-range, defined in [RFC4647], Section 2.1&gt;
[690]2419<x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in [RFC5646], Section 2.1&gt;
2421<x:ref>media-range</x:ref> = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
[425]2422 ";" OWS parameter )
[427]2423<x:ref>media-type</x:ref> = type "/" subtype *( OWS ";" OWS parameter )
2425<x:ref>parameter</x:ref> = attribute "=" value
[1318]2426<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
[1587]2428<x:ref>qvalue</x:ref> = &lt;qvalue, defined in [Part1], Section 4.3.1&gt;
2430<x:ref>subtype</x:ref> = token
[1523]2432<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.4&gt;
[427]2433<x:ref>type</x:ref> = token
[810]2435<x:ref>value</x:ref> = word
[1523]2437<x:ref>word</x:ref> = &lt;word, defined in [Part1], Section 3.2.4&gt;
[532]2440<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
2441; Accept defined but not used
[425]2442; Accept-Charset defined but not used
2443; Accept-Encoding defined but not used
2444; Accept-Language defined but not used
[968]2445; Content-Encoding defined but not used
2446; Content-Language defined but not used
2447; Content-Location defined but not used
2448; Content-Type defined but not used
[425]2449; MIME-Version defined but not used
[680]2451<?ENDINC p3-payload.abnf-appendix ?>
[252]2453<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
[1002]2455<section title="Since RFC 2616">
2457  Extracted relevant partitions from <xref target="RFC2616"/>.
2461<section title="Since draft-ietf-httpbis-p3-payload-00">
[116]2463  Closed issues:
2464  <list style="symbols">
2465    <t>
[324]2466      <eref target=""/>:
[116]2467      "Media Type Registrations"
2468      (<eref target=""/>)
2469    </t>
2470    <t>
[324]2471      <eref target=""/>:
[116]2472      "Clarification regarding quoting of charset values"
2473      (<eref target=""/>)
2474    </t>
2475    <t>
[324]2476      <eref target=""/>:
[116]2477      "Remove 'identity' token references"
2478      (<eref target=""/>)
2479    </t>
2480    <t>
[324]2481      <eref target=""/>:
[126]2482      "Accept-Encoding BNF"
2483    </t>
2484    <t>
[324]2485      <eref target=""/>:
[152]2486      "Normative and Informative references"
2487    </t>
2488    <t>
[324]2489      <eref target=""/>:
[116]2490      "RFC1700 references"
2491    </t>
[122]2492    <t>
[324]2493      <eref target=""/>:
[200]2494      "Updating to RFC4288"
2495    </t>
2496    <t>
[324]2497      <eref target=""/>:
[129]2498      "Informative references"
2499    </t>
2500    <t>
[324]2501      <eref target=""/>:
[123]2502      "ISO-8859-1 Reference"
2503    </t>
2504    <t>
[324]2505      <eref target=""/>:
[122]2506      "Encoding References Normative"
2507    </t>
[131]2508    <t>
[324]2509      <eref target=""/>:
[131]2510      "Normative up-to-date references"
2511    </t>
[116]2512  </list>
[170]2516<section title="Since draft-ietf-httpbis-p3-payload-01">
[324]2518  Ongoing work on ABNF conversion (<eref target=""/>):
[205]2519  <list style="symbols">
2520    <t>
2521      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2522    </t>
2523  </list>
[252]2527<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
[232]2529  Closed issues:
2530  <list style="symbols">
2531    <t>
[324]2532      <eref target=""/>:
[251]2533      "Quoting Charsets"
2534    </t>
2535    <t>
[324]2536      <eref target=""/>:
[232]2537      "Classification for Allow header"
2538    </t>
[248]2539    <t>
[324]2540      <eref target=""/>:
[248]2541      "missing default for qvalue in description of Accept-Encoding"
2542    </t>
[232]2543  </list>
[994]2546  Ongoing work on IANA Message Header Field Registration (<eref target=""/>):
[253]2547  <list style="symbols">
2548    <t>
[994]2549      Reference RFC 3984, and update header field registrations for headers defined
[253]2550      in this document.
2551    </t>
2552  </list>
[267]2556<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
[269]2558  Closed issues:
2559  <list style="symbols">
2560    <t>
[297]2561      <eref target=""/>:
2562      "Quoting Charsets"
2563    </t>
2564    <t>
[303]2565      <eref target=""/>:
2566      "language tag matching (Accept-Language) vs RFC4647"
2567    </t>
2568    <t>
[277]2569      <eref target=""/>:
[269]2570      "RFC 1806 has been replaced by RFC2183"
2571    </t>
2572  </list>
2575  Other changes:
2576  <list style="symbols">
2577    <t>
2578      <eref target=""/>:
[1101]2579      "Encoding References Normative" &mdash; rephrase the annotation and reference
[1477]2580      BCP97.
[277]2581    </t>
2582  </list>
[269]2584 </section>
[323]2586<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
[327]2588  Closed issues:
2589  <list style="symbols">
2590    <t>
2591      <eref target=""/>:
2592      "RFC 2822 is updated by RFC 5322"
2593    </t>
2594  </list>
2597  Ongoing work on ABNF conversion (<eref target=""/>):
2598  <list style="symbols">
2599    <t>
2600      Use "/" instead of "|" for alternatives.
2601    </t>
[357]2602    <t>
2603      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
2604      whitespace ("OWS") and required whitespace ("RWS").
2605    </t>
2606    <t>
2607      Rewrite ABNFs to spell out whitespace rules, factor out
[994]2608      header field value format definitions.
[357]2609    </t>
[334]2610  </list>
[382]2614<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
[385]2616  Closed issues:
2617  <list style="symbols">
2618    <t>
2619      <eref target=""/>:
2620      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
2621    </t>
2622  </list>
[543]2625  Final work on ABNF conversion (<eref target=""/>):
[421]2626  <list style="symbols">
2627    <t>
[424]2628      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
[421]2629    </t>
2630  </list>
2633  Other changes:
2634  <list style="symbols">
2635    <t>
2636      Move definition of quality values into Part 1.
2637    </t>
2638  </list>
[547]2642<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
[577]2644  Closed issues:
2645  <list style="symbols">
2646    <t>
2647      <eref target=""/>:
2648      "Content-Location isn't special"
2649    </t>
[592]2650    <t>
2651      <eref target=""/>:
2652      "Content Sniffing"
2653    </t>
[577]2654  </list>
[604]2658<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
[613]2660  Closed issues:
2661  <list style="symbols">
2662    <t>
[670]2663      <eref target=""/>:
[613]2664      "Updated reference for language tags"
2665    </t>
[663]2666    <t>
[716]2667      <eref target=""/>:
2668      "Clarify rules for determining what entities a response carries"
2669    </t>
2670    <t>
[712]2671      <eref target=""/>:
2672      "Content-Location base-setting problems"
2673    </t>
2674    <t>
[663]2675      <eref target=""/>:
2676      "Content Sniffing"
2677    </t>
[670]2678    <t>
2679      <eref target=""/>:
2680      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
2681    </t>
[673]2682    <t>
2683      <eref target=""/>:
2684      "move definitions of gzip/deflate/compress to part 1"
2685    </t>
[613]2686  </list>
2689  Partly resolved issues:
2690  <list style="symbols">
2691    <t>
2692      <eref target=""/>:
2693      "update IANA requirements wrt Transfer-Coding values" (add the
2694      IANA Considerations subsection)
2695    </t>
[668]2696    <t>
2697      <eref target=""/>:
2698      "update IANA requirements wrt Content-Coding values" (add the
2699      IANA Considerations subsection)
2700    </t>
[667]2701  </list>
[720]2705<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
[724]2707  Closed issues:
2708  <list style="symbols">
2709    <t>
[745]2710      <eref target=""/>:
2711      "Content Negotiation for media types"
2712    </t>
2713    <t>
[724]2714      <eref target=""/>:
2715      "Accept-Language: which RFC4647 filtering?"
2716    </t>
2717  </list>
[773]2721<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
[808]2723  Closed issues:
2724  <list style="symbols">
2725    <t>
[937]2726      <eref target=""/>:
2727      "MIME-Version not listed in P1, general header fields"
2728    </t>
2729    <t>
[808]2730      <eref target=""/>:
2731      "IANA registry for content/transfer encodings"
2732    </t>
[810]2733    <t>
[831]2734      <eref target=""/>:
2735      "Content Sniffing"
2736    </t>
2737    <t>
[810]2738      <eref target=""/>:
2739      "use of term "word" when talking about header structure"
2740    </t>
[808]2741  </list>
2744  Partly resolved issues:
2745  <list style="symbols">
2746    <t>
2747      <eref target=""/>:
2748      "Term for the requested resource's URI"
2749    </t>
2750  </list>
[841]2754<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
[854]2756  Closed issues:
2757  <list style="symbols">
2758    <t>
[858]2759      <eref target=""/>:
2760      "Clarify 'Requested Variant'"
2761    </t>
2762    <t>
2763      <eref target=""/>:
2764      "Content-Location isn't special"
2765    </t>
2766    <t>
[854]2767      <eref target=""/>:
2768      "Delimiting messages with multipart/byteranges"
2769    </t>
[858]2770    <t>
2771      <eref target=""/>:
2772      "Clarify entity / representation / variant terminology"
2773    </t>
2774    <t>
2775      <eref target=""/>:
2776      "confusing req. language for Content-Location"
2777    </t>
2778    <t>
2779      <eref target=""/>:
2780      "Content-Location on 304 responses"
2781    </t>
[882]2782    <t>
2783      <eref target=""/>:
2784      "'requested resource' in content-encoding definition"
2785    </t>
[911]2786    <t>
2787      <eref target=""/>:
2788      "consider removing the 'changes from 2068' sections"
2789    </t>
[854]2790  </list>
2793  Partly resolved issues:
2794  <list style="symbols">
2795    <t>
2796      <eref target=""/>:
2797      "Content-MD5 and partial responses"
2798    </t>
2799  </list>
[973]2803<section title="Since draft-ietf-httpbis-p3-payload-11" anchor="changes.since.11">
[987]2805  Closed issues:
2806  <list style="symbols">
2807    <t>
2808      <eref target=""/>:
2809      "Factor out Content-Disposition"
2810    </t>
2811  </list>
[1052]2815<section title="Since draft-ietf-httpbis-p3-payload-12" anchor="changes.since.12">
[1153]2817  Closed issues:
2818  <list style="symbols">
2819    <t>
[1165]2820      <eref target=""/>:
2821      "Header Classification"
2822    </t>
2823    <t>
[1167]2824      <eref target=""/>:
2825      "untangle ABNFs for header fields"
2826    </t>
2827    <t>
[1153]2828      <eref target=""/>:
2829      "potentially misleading MAY in media-type def"
2830    </t>
2831  </list>
[1180]2835<section title="Since draft-ietf-httpbis-p3-payload-13" anchor="changes.since.13">
[1234]2837  Closed issues:
2838  <list style="symbols">
2839    <t>
[1240]2840      <eref target=""/>:
2841      "Default charsets for text media types"
2842    </t>
2843    <t>
[1267]2844      <eref target=""/>:
2845      "Content-MD5 and partial responses"
2846    </t>
2847    <t>
[1234]2848      <eref target=""/>:
2849      "untangle ABNFs for header fields"
2850    </t>
[1244]2851    <t>
2852      <eref target=""/>:
2853      "confusing undefined parameter in media range example"
2854    </t>
[1234]2855  </list>
[1271]2859<section title="Since draft-ietf-httpbis-p3-payload-14" anchor="changes.since.14">
[1328]2861  None.
[1326]2865<section title="Since draft-ietf-httpbis-p3-payload-15" anchor="changes.since.15">
[1335]2867  Closed issues:
2868  <list style="symbols">
2869    <t>
2870      <eref target=""/>:
2871      "Strength of requirements on Accept re: 406"
2872    </t>
2873  </list>
[1401]2877<section title="Since draft-ietf-httpbis-p3-payload-16" anchor="changes.since.16">
[1452]2879  Closed issues:
2880  <list style="symbols">
2881    <t>
2882      <eref target=""/>:
2883      "Document HTTP's error-handling philosophy"
2884    </t>
2885  </list>
[1467]2889<section title="Since draft-ietf-httpbis-p3-payload-17" anchor="changes.since.17">
[1477]2891  Closed issues:
2892  <list style="symbols">
2893    <t>
2894      <eref target=""/>:
2895      "intended maturity level vs normative references"
2896    </t>
2897  </list>
[1499]2901<section title="Since draft-ietf-httpbis-p3-payload-18" anchor="changes.since.18">
[1567]2903  Closed issues:
2904  <list style="symbols">
2905    <t>
[1573]2906      <eref target=""/>:
2907      "is ETag a representation header field?"
2908    </t>
2909    <t>
[1593]2910      <eref target=""/>:
2911      "Content-Location doesn't constrain the cardinality of representations"
2912    </t>
2913    <t>
[1567]2914      <eref target=""/>:
2915      "make IANA policy definitions consistent"
2916    </t>
2917  </list>
[1592]2921<section title="Since draft-ietf-httpbis-p3-payload-19" anchor="changes.since.19">
2923  None yet.
Note: See TracBrowser for help on using the repository browser.