source: draft-ietf-httpbis/latest/p3-payload.xml @ 852

Last change on this file since 852 was 852, checked in by fielding@…, 10 years ago

Changed message-body ABNF to be *OCTET. Specifying the actual
number of octets will have to be done in prose.

Moved mistitled "Message Length" section into the Message Body
section, since it only explains how many octets are in the body.
Deleted useless "Entity Length" section and transfer-length term.

Addresses #28: Connection closing

Removed redundant mention of terminating by connection close
and rewrote explanation so that it doesn't self-contradict.

Addresses #90: Delimiting messages with multipart/byteranges

Removed message-delimiting paragraphs of multipart/byteranges
from p1 and p3.

Addresses #95: Handling multiple Content-Length headers

Added requirements for what to do if multiple or invalid
Content-Length is received.

Rephrased requirements for Transfer-Encoding to only apply
when a transfer-coding is present. Clarify that Transfer-Encoding
overrides Content-Length and treat receiving both as an error.
Clarify that only the chunked transfer-coding can delimit a
message (the original design allowed other self-descriptive
encodings, but that was abandoned in 2616).

Addresses #109: Clarify entity / representation / variant terminology

Entity-body terminology changed to payload in order to clarify that
it is what gets packaged (as a message-body) into a message,
allowing us to (eventually) distinguish between messages containing
whole representations and messages containing only partial
representations. Reduce use of the same terms for other things
(e.g., in explanation of dates).

  • Property svn:eol-style set to native
File size: 132.9 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">
[832]15  <!ENTITY ID-MONTH "July">
[741]16  <!ENTITY ID-YEAR "2010">
[424]17  <!ENTITY notation                 "<xref target='Part1' x:rel='#notation' xmlns:x=''/>">
[205]18  <!ENTITY notation-abnf            "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
19  <!ENTITY basic-rules              "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
[115]20  <!ENTITY caching-neg-resp         "<xref target='Part6' x:rel='#caching.negotiated.responses' xmlns:x=''/>">
[31]21  <!ENTITY header-transfer-encoding "<xref target='Part1' x:rel='#header.transfer-encoding' xmlns:x=''/>">
22  <!ENTITY header-content-length    "<xref target='Part1' x:rel='#header.content-length' xmlns:x=''/>">
23  <!ENTITY header-content-range     "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
24  <!ENTITY header-expires           "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
25  <!ENTITY header-last-modified     "<xref target='Part4' x:rel='#header.last-modified' xmlns:x=''/>">
26  <!ENTITY header-user-agent        "<xref target='Part2' x:rel='#header.user-agent' xmlns:x=''/>">
[115]27  <!ENTITY header-vary              "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
[31]28  <!ENTITY message-body             "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
[852]29  <!ENTITY message-length           "<xref target='Part1' x:rel='#message.body.length' xmlns:x=''/>">
[647]30  <!ENTITY header-fields            "<xref target='Part1' x:rel='#header.fields' xmlns:x=''/>">
[31]31  <!ENTITY multipart-byteranges     "<xref target='Part5' x:rel='' xmlns:x=''/>">
[580]32  <!ENTITY full-date                "<xref target='Part1' x:rel='' xmlns:x=''/>">
[457]33  <!ENTITY qvalue                   "<xref target='Part1' x:rel='#quality.values' xmlns:x=''/>">
[374]34  <!ENTITY uri                      "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
[823]35  <!ENTITY effective-request-uri    "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x=''/>">
[808]36  <!ENTITY compression-codings      "<xref target='Part1' x:rel='#compression.codings' xmlns:x=''/>">
37  <!ENTITY transfer-codings         "<xref target='Part1' x:rel='#transfer.codings' xmlns:x=''/>">
[673]38  <!ENTITY compress-coding          "<xref target='Part1' x:rel='#compress.coding' xmlns:x=''/>">
39  <!ENTITY deflate-coding           "<xref target='Part1' x:rel='#deflate.coding' xmlns:x=''/>">
40  <!ENTITY gzip-coding              "<xref target='Part1' x:rel='#gzip.coding' xmlns:x=''/>">
[716]41  <!ENTITY response-representation  "<xref target='Part2' x:rel='#identifying.response.associated.with.representation' xmlns:x=''/>">
43<?rfc toc="yes" ?>
[29]44<?rfc symrefs="yes" ?>
45<?rfc sortrefs="yes" ?>
[8]46<?rfc compact="yes"?>
47<?rfc subcompact="no" ?>
48<?rfc linkmailto="no" ?>
49<?rfc editing="no" ?>
[203]50<?rfc comments="yes"?>
51<?rfc inline="yes"?>
[799]52<?rfc rfcedstyle="yes"?>
[8]53<?rfc-ext allow-markup-in-artwork="yes" ?>
54<?rfc-ext include-references-in-index="yes" ?>
[308]55<rfc obsoletes="2616" category="std" x:maturity-level="draft"
[446]56     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p3-payload-&ID-VERSION;"
[153]57     xmlns:x=''>
[120]60  <title abbrev="HTTP/1.1, Part 3">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
[29]62  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
63    <organization abbrev="Day Software">Day Software</organization>
[8]64    <address>
65      <postal>
[29]66        <street>23 Corporate Plaza DR, Suite 280</street>
67        <city>Newport Beach</city>
[8]68        <region>CA</region>
[29]69        <code>92660</code>
70        <country>USA</country>
[8]71      </postal>
[29]72      <phone>+1-949-706-5300</phone>
73      <facsimile>+1-949-706-5305</facsimile>
74      <email></email>
75      <uri></uri>
[8]76    </address>
77  </author>
[29]79  <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]80    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
[8]81    <address>
82      <postal>
[29]83        <street>21 Oak Knoll Road</street>
84        <city>Carlisle</city>
[8]85        <region>MA</region>
[29]86        <code>01741</code>
87        <country>USA</country>
[8]88      </postal>
[844]89      <email></email>
90      <uri></uri>
[8]91    </address>
92  </author>
94  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
[29]95    <organization abbrev="HP">Hewlett-Packard Company</organization>
[8]96    <address>
97      <postal>
[29]98        <street>HP Labs, Large Scale Systems Group</street>
99        <street>1501 Page Mill Road, MS 1177</street>
[8]100        <city>Palo Alto</city>
101        <region>CA</region>
[29]102        <code>94304</code>
103        <country>USA</country>
[8]104      </postal>
[29]105      <email></email>
[8]106    </address>
107  </author>
109  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
[29]110    <organization abbrev="Microsoft">Microsoft Corporation</organization>
[8]111    <address>
112      <postal>
[29]113        <street>1 Microsoft Way</street>
114        <city>Redmond</city>
115        <region>WA</region>
116        <code>98052</code>
117        <country>USA</country>
[8]118      </postal>
[29]119      <email></email>
[8]120    </address>
121  </author>
123  <author initials="L." surname="Masinter" fullname="Larry Masinter">
[29]124    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
[8]125    <address>
126      <postal>
[29]127        <street>345 Park Ave</street>
128        <city>San Jose</city>
[8]129        <region>CA</region>
[29]130        <code>95110</code>
131        <country>USA</country>
[8]132      </postal>
[29]133      <email></email>
134      <uri></uri>
[8]135    </address>
136  </author>
138  <author initials="P." surname="Leach" fullname="Paul J. Leach">
139    <organization abbrev="Microsoft">Microsoft Corporation</organization>
140    <address>
141      <postal>
142        <street>1 Microsoft Way</street>
143        <city>Redmond</city>
144        <region>WA</region>
145        <code>98052</code>
146      </postal>
147      <email></email>
148    </address>
149  </author>
151  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
152    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
153    <address>
154      <postal>
[34]155        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
156        <street>The Stata Center, Building 32</street>
157        <street>32 Vassar Street</street>
[8]158        <city>Cambridge</city>
159        <region>MA</region>
160        <code>02139</code>
[29]161        <country>USA</country>
[8]162      </postal>
163      <email></email>
[34]164      <uri></uri>
[8]165    </address>
166  </author>
[95]168  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]169    <organization abbrev="W3C">World Wide Web Consortium</organization>
170    <address>
171      <postal>
172        <street>W3C / ERCIM</street>
173        <street>2004, rte des Lucioles</street>
174        <city>Sophia-Antipolis</city>
175        <region>AM</region>
176        <code>06902</code>
177        <country>France</country>
178      </postal>
179      <email></email>
180      <uri></uri>
181    </address>
182  </author>
[95]184  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
185    <organization abbrev="greenbytes">greenbytes GmbH</organization>
186    <address>
187      <postal>
188        <street>Hafenweg 16</street>
189        <city>Muenster</city><region>NW</region><code>48155</code>
190        <country>Germany</country>
191      </postal>
[609]192      <phone>+49 251 2807760</phone>
193      <facsimile>+49 251 2807761</facsimile>
194      <email></email>
195      <uri></uri>
[95]196    </address>
197  </author>
[31]199  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
[440]200  <workgroup>HTTPbis Working Group</workgroup>
204   The Hypertext Transfer Protocol (HTTP) is an application-level
205   protocol for distributed, collaborative, hypermedia information
[29]206   systems. HTTP has been in use by the World Wide Web global information
[35]207   initiative since 1990. This document is Part 3 of the seven-part specification
[29]208   that defines the protocol referred to as "HTTP/1.1" and, taken together,
[42]209   obsoletes RFC 2616.  Part 3 defines HTTP message content,
[29]210   metadata, and content negotiation.
214<note title="Editorial Note (To be removed by RFC Editor)">
215  <t>
216    Discussion of this draft should take place on the HTTPBIS working group
217    mailing list ( The current issues list is
[848]218    at <eref target=""/>
[36]219    and related documents (including fancy diffs) can be found at
[324]220    <eref target=""/>.
[36]221  </t>
[153]222  <t>
[841]223    The changes in this draft are summarized in <xref target="changes.since.10"/>.
[153]224  </t>
228<section title="Introduction" anchor="introduction">
[163]230   This document defines HTTP/1.1 message payloads (a.k.a., content), the
[161]231   associated metadata header fields that define how the payload is intended
232   to be interpreted by a recipient, the request header fields that
233   may influence content selection, and the various selection algorithms
234   that are collectively referred to as HTTP content negotiation.
237   This document is currently disorganized in order to minimize the changes
238   between drafts and enable reviewers to see the smaller errata changes.
239   The next draft will reorganize the sections to better reflect the content.
240   In particular, the sections on entities will be renamed payload and moved
241   to the first half of the document, while the sections on content negotiation
242   and associated request header fields will be moved to the second half.  The
243   current mess reflects how widely dispersed these topics and associated
244   requirements had become in <xref target="RFC2616"/>.
[660]247<section title="Terminology" anchor="terminology">
249   This specification uses a number of terms to refer to the roles
250   played by participants in, and objects of, the HTTP communication.
253  <iref item="content negotiation"/>
254  <x:dfn>content negotiation</x:dfn>
255  <list>
256    <t>
257      The mechanism for selecting the appropriate representation when
258      servicing a request. The representation of entities in any response
259      can be negotiated (including error responses).
260    </t>
261  </list>
264  <iref item="entity"/>
265  <x:dfn>entity</x:dfn>
266  <list>
267    <t>
268      The information transferred as the payload of a request or
269      response. An entity consists of metadata in the form of
270      entity-header fields and content in the form of an entity-body.
271    </t>
272  </list>
275  <iref item="representation"/>
276  <x:dfn>representation</x:dfn>
277  <list>
278    <t>
279      An entity included with a response that is subject to content
280      negotiation. There may exist multiple
281      representations associated with a particular response status.
282    </t>
283  </list>
286  <iref item="variant"/>
287  <x:dfn>variant</x:dfn>
288  <list>
289    <t>
290      A resource may have one, or more than one, representation(s)
291      associated with it at any given instant. Each of these
[746]292      representations is termed a "variant".  Use of the term "variant"
[660]293      does not necessarily imply that the resource is subject to content
294      negotiation.
295    </t>
296  </list>
[96]300<section title="Requirements" anchor="intro.requirements">
302   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
303   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
304   document are to be interpreted as described in <xref target="RFC2119"/>.
307   An implementation is not compliant if it fails to satisfy one or more
[847]308   of the "MUST" or "REQUIRED" level requirements for the protocols it
309   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
310   level and all the "SHOULD" level requirements for its protocols is said
311   to be "unconditionally compliant"; one that satisfies all the "MUST"
312   level requirements but not all the "SHOULD" level requirements for its
313   protocols is said to be "conditionally compliant".
[424]317<section title="Syntax Notation" anchor="notation">
[425]318  <x:anchor-alias value="ALPHA"/>
319  <x:anchor-alias value="CR"/>
320  <x:anchor-alias value="DIGIT"/>
321  <x:anchor-alias value="LF"/>
322  <x:anchor-alias value="OCTET"/>
323  <x:anchor-alias value="VCHAR"/>
324  <x:anchor-alias value="WSP"/>
[543]326  This specification uses the ABNF syntax defined in &notation; (which
327  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
328  <xref target="collected.abnf"/> shows the collected ABNF, with the list
329  rule expanded.
[425]332  The following core rules are included by
333  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
334  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
335  DIGIT (decimal 0-9), DQUOTE (double quote),
336  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
337  OCTET (any 8-bit sequence of data), SP (space),
338  VCHAR (any visible USASCII character),
339  and WSP (whitespace).
342<section title="Core Rules" anchor="core.rules">
[229]343  <x:anchor-alias value="quoted-string"/>
344  <x:anchor-alias value="token"/>
[810]345  <x:anchor-alias value="word"/>
[357]346  <x:anchor-alias value="OWS"/>
[424]348  The core rules below are defined in &basic-rules;:
350<figure><artwork type="abnf2616">
[229]351  <x:ref>quoted-string</x:ref>  = &lt;quoted-string, defined in &basic-rules;&gt;
352  <x:ref>token</x:ref>          = &lt;token, defined in &basic-rules;&gt;
[810]353  <x:ref>word</x:ref>           = &lt;word, defined in &basic-rules;&gt;
[357]354  <x:ref>OWS</x:ref>            = &lt;OWS, defined in &basic-rules;&gt;
358<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]359  <x:anchor-alias value="absolute-URI"/>
[229]360  <x:anchor-alias value="Allow"/>
361  <x:anchor-alias value="Content-Length"/>
362  <x:anchor-alias value="Content-Range"/>
363  <x:anchor-alias value="Expires"/>
364  <x:anchor-alias value="Last-Modified"/>
[647]365  <x:anchor-alias value="header-field"/>
[391]366  <x:anchor-alias value="partial-URI"/>
[457]367  <x:anchor-alias value="qvalue"/>
[206]369  The ABNF rules below are defined in other parts:
[207]371<figure><!--Part1--><artwork type="abnf2616">
[374]372  <x:ref>absolute-URI</x:ref>   = &lt;absolute-URI, defined in &uri;&gt;
[229]373  <x:ref>Content-Length</x:ref> = &lt;Content-Length, defined in &header-content-length;&gt;
[647]374  <x:ref>header-field</x:ref>   = &lt;header-field, defined in &header-fields;&gt;
[391]375  <x:ref>partial-URI</x:ref>    = &lt;partial-URI, defined in &uri;&gt;
[457]376  <x:ref>qvalue</x:ref>         = &lt;qvalue, defined in &qvalue;&gt;
378<figure><!--Part4--><artwork type="abnf2616">
[229]379  <x:ref>Last-Modified</x:ref>  = &lt;Last-Modified, defined in &header-last-modified;&gt;
381<figure><!--Part5--><artwork type="abnf2616">
[229]382  <x:ref>Content-Range</x:ref>  = &lt;Content-Range, defined in &header-content-range;&gt;
384<figure><!--Part6--><artwork type="abnf2616">
[229]385  <x:ref>Expires</x:ref>        = &lt;Expires, defined in &header-expires;&gt;
[8]393<section title="Protocol Parameters" anchor="protocol.parameters">
395<section title="Character Sets" anchor="character.sets">
397   HTTP uses the same definition of the term "character set" as that
398   described for MIME:
401   The term "character set" is used in this document to refer to a
402   method used with one or more tables to convert a sequence of octets
403   into a sequence of characters. Note that unconditional conversion in
404   the other direction is not required, in that not all characters may
405   be available in a given character set and a character set may provide
406   more than one sequence of octets to represent a particular character.
407   This definition is intended to allow various kinds of character
408   encoding, from simple single-table mappings such as US-ASCII to
409   complex table switching methods such as those that use ISO-2022's
410   techniques. However, the definition associated with a MIME character
411   set name &MUST; fully specify the mapping to be performed from octets
412   to characters. In particular, use of external profiling information
413   to determine the exact mapping is not permitted.
416  <t>
417    <x:h>Note:</x:h> This use of the term "character set" is more commonly
418    referred to as a "character encoding." However, since HTTP and
419    MIME share the same registry, it is important that the terminology
420    also be shared.
421  </t>
[229]423<t anchor="rule.charset">
424  <x:anchor-alias value="charset"/>
[8]425   HTTP character sets are identified by case-insensitive tokens. The
426   complete set of tokens is defined by the IANA Character Set registry
[91]427   (<eref target=""/>).
429<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="charset"/>
[229]430  <x:ref>charset</x:ref> = <x:ref>token</x:ref>
433   Although HTTP allows an arbitrary token to be used as a charset
434   value, any token that has a predefined value within the IANA
[91]435   Character Set registry &MUST; represent the character set defined
[8]436   by that registry. Applications &SHOULD; limit their use of character
437   sets to those defined by the IANA registry.
[81]440   HTTP uses charset in two contexts: within an Accept-Charset request
441   header (in which the charset value is an unquoted token) and as the
[115]442   value of a parameter in a Content-Type header (within a request or
[81]443   response), in which case the parameter value of the charset parameter
444   may be quoted.
[129]447   Implementors should be aware of IETF character set requirements <xref target="RFC3629"/>
[8]448   <xref target="RFC2277"/>.
451<section title="Missing Charset" anchor="missing.charset">
453   Some HTTP/1.0 software has interpreted a Content-Type header without
454   charset parameter incorrectly to mean "recipient should guess."
455   Senders wishing to defeat this behavior &MAY; include a charset
456   parameter even when the charset is ISO-8859-1 (<xref target="ISO-8859-1"/>) and &SHOULD; do so when
457   it is known that it will not confuse the recipient.
460   Unfortunately, some older HTTP/1.0 clients did not deal properly with
461   an explicit charset parameter. HTTP/1.1 recipients &MUST; respect the
462   charset label provided by the sender; and those user agents that have
463   a provision to "guess" a charset &MUST; use the charset from the
464   content-type field if they support that charset, rather than the
465   recipient's preference, when initially displaying a document. See
466   <xref target="canonicalization.and.text.defaults"/>.
471<section title="Content Codings" anchor="content.codings">
[229]472  <x:anchor-alias value="content-coding"/>
474   Content coding values indicate an encoding transformation that has
475   been or can be applied to an entity. Content codings are primarily
476   used to allow a document to be compressed or otherwise usefully
477   transformed without losing the identity of its underlying media type
478   and without loss of information. Frequently, the entity is stored in
479   coded form, transmitted directly, and only decoded by the recipient.
481<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-coding"/>
[229]482  <x:ref>content-coding</x:ref>   = <x:ref>token</x:ref>
485   All content-coding values are case-insensitive. HTTP/1.1 uses
486   content-coding values in the Accept-Encoding (<xref target="header.accept-encoding"/>) and
487   Content-Encoding (<xref target="header.content-encoding"/>) header fields. Although the value
488   describes the content-coding, what is more important is that it
489   indicates what decoding mechanism will be required to remove the
490   encoding.
[673]493   compress<iref item="compress (Coding Format)"/><iref item="Coding Format" subitem="compress"/>
494  <list>
495    <t>
496      See &compress-coding;.
497    </t>
498  </list>
[673]501   deflate<iref item="deflate (Coding Format)"/><iref item="Coding Format" subitem="deflate"/>
[8]502  <list>
503    <t>
[673]504      See &deflate-coding;.
[8]505    </t>
506  </list>
[673]509   gzip<iref item="gzip (Coding Format)"/><iref item="Coding Format" subitem="gzip"/>
510  <list>
511    <t>
512      See &gzip-coding;.
513    </t>
514  </list>
[673]517   identity<iref item="identity (Coding Format)"/><iref item="Coding Format" subitem="identity"/>
[8]518  <list><t>
519        The default (identity) encoding; the use of no transformation
520        whatsoever. This content-coding is used only in the Accept-Encoding
521        header, and &SHOULD-NOT;  be used in the Content-Encoding
522        header.
523  </t></list>
526<section title="Content Coding Registry" anchor="content.coding.registry">
[670]528   The HTTP Content Coding Registry defines the name space for the content
529   coding names.
532   Registrations &MUST; include the following fields:
533   <list style="symbols">
534     <t>Name</t>
535     <t>Description</t>
536     <t>Pointer to specification text</t>
537   </list>
[808]540   Names of content codings &MUST-NOT; overlap with names of transfer codings
541   (&transfer-codings;), unless the encoding transformation is identical (as it
542   is the case for the compression codings defined in
543   &compression-codings;).
[670]546   Values to be added to this name space require expert review and a specification
547   (see "Expert Review" and "Specification Required" in
548   <xref target="RFC5226" x:fmt="of" x:sec="4.1"/>), and &MUST;
[8]549   conform to the purpose of content coding defined in this section.
552   The registry itself is maintained at
553   <eref target=""/>.
[8]559<section title="Media Types" anchor="media.types">
[229]560  <x:anchor-alias value="media-type"/>
561  <x:anchor-alias value="type"/>
562  <x:anchor-alias value="subtype"/>
[152]564   HTTP uses Internet Media Types <xref target="RFC2046"/> in the Content-Type (<xref target="header.content-type"/>)
[8]565   and Accept (<xref target="header.accept"/>) header fields in order to provide
566   open and extensible data typing and type negotiation.
568<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]569  <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> )
570  <x:ref>type</x:ref>       = <x:ref>token</x:ref>
571  <x:ref>subtype</x:ref>    = <x:ref>token</x:ref>
[229]573<t anchor="rule.parameter">
574  <x:anchor-alias value="attribute"/>
575  <x:anchor-alias value="parameter"/>
576  <x:anchor-alias value="value"/>
[8]577   Parameters &MAY; follow the type/subtype in the form of attribute/value
[29]578   pairs.
[29]580<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]581  <x:ref>parameter</x:ref>      = <x:ref>attribute</x:ref> "=" <x:ref>value</x:ref>
582  <x:ref>attribute</x:ref>      = <x:ref>token</x:ref>
[810]583  <x:ref>value</x:ref>          = <x:ref>word</x:ref>
586   The type, subtype, and parameter attribute names are case-insensitive.
[370]587   Parameter values might or might not be case-sensitive, depending on the
588   semantics of the parameter name.  The presence or absence of a parameter might
[8]589   be significant to the processing of a media-type, depending on its
590   definition within the media type registry.
[297]593   A parameter value that matches the <x:ref>token</x:ref> production may be
594   transmitted as either a token or within a quoted-string. The quoted and
595   unquoted values are equivalent.
[8]598   Note that some older HTTP applications do not recognize media type
599   parameters. When sending data to older HTTP applications,
600   implementations &SHOULD; only use media type parameters when they are
601   required by that type/subtype definition.
604   Media-type values are registered with the Internet Assigned Number
[91]605   Authority (IANA). The media type registration process is
[115]606   outlined in <xref target="RFC4288"/>. Use of non-registered media types is
[8]607   discouraged.
610<section title="Canonicalization and Text Defaults" anchor="canonicalization.and.text.defaults">
612   Internet media types are registered with a canonical form. An
613   entity-body transferred via HTTP messages &MUST; be represented in the
614   appropriate canonical form prior to its transmission except for
615   "text" types, as defined in the next paragraph.
618   When in canonical form, media subtypes of the "text" type use CRLF as
619   the text line break. HTTP relaxes this requirement and allows the
620   transport of text media with plain CR or LF alone representing a line
621   break when it is done consistently for an entire entity-body. HTTP
622   applications &MUST; accept CRLF, bare CR, and bare LF as being
623   representative of a line break in text media received via HTTP. In
624   addition, if the text is represented in a character set that does not
625   use octets 13 and 10 for CR and LF respectively, as is the case for
626   some multi-byte character sets, HTTP allows the use of whatever octet
627   sequences are defined by that character set to represent the
628   equivalent of CR and LF for line breaks. This flexibility regarding
629   line breaks applies only to text media in the entity-body; a bare CR
630   or LF &MUST-NOT; be substituted for CRLF within any of the HTTP control
631   structures (such as header fields and multipart boundaries).
634   If an entity-body is encoded with a content-coding, the underlying
635   data &MUST; be in a form defined above prior to being encoded.
[211]638   The "charset" parameter is used with some media types to define the
639   character set (<xref target="character.sets"/>) of the data. When no explicit charset
640   parameter is provided by the sender, media subtypes of the "text"
641   type are defined to have a default charset value of "ISO-8859-1" when
642   received via HTTP. Data in character sets other than "ISO-8859-1" or
643   its subsets &MUST; be labeled with an appropriate charset value. See
644   <xref target="missing.charset"/> for compatibility problems.
648<section title="Multipart Types" anchor="multipart.types">
650   MIME provides for a number of "multipart" types -- encapsulations of
651   one or more entities within a single message-body. All multipart
[97]652   types share a common syntax, as defined in <xref target="RFC2046" x:sec="5.1.1" x:fmt="of"/>,
653   and &MUST; include a boundary parameter as part of the media type
[8]654   value. The message body is itself a protocol element and &MUST;
655   therefore use only CRLF to represent line breaks between body-parts.
658   In general, HTTP treats a multipart message-body no differently than
[852]659   any other media type: strictly as payload.  HTTP does not use the
660   multipart boundary as an indicator of message-body length.
[97]661   <!-- jre: re-insert removed text pointing to caching? -->
[852]662   In all other respects, an HTTP user agent &SHOULD; follow the same or similar
[8]663   behavior as a MIME user agent would upon receipt of a multipart type.
664   The MIME header fields within each body-part of a multipart message-body
665   do not have any significance to HTTP beyond that defined by
666   their MIME semantics.
669   If an application receives an unrecognized multipart subtype, the
670   application &MUST; treat it as being equivalent to "multipart/mixed".
673  <t>
674    <x:h>Note:</x:h> The "multipart/form-data" type has been specifically defined
675    for carrying form data suitable for processing via the POST
676    request method, as described in <xref target="RFC2388"/>.
677  </t>
682<section title="Language Tags" anchor="language.tags">
[229]683  <x:anchor-alias value="language-tag"/>
[690]685   A language tag, as defined in <xref target="RFC5646"/>, identifies a
[613]686   natural language spoken, written, or otherwise conveyed by human beings for
687   communication of information to other human beings. Computer languages are
688   explicitly excluded. HTTP uses language tags within the Accept-Language and
689   Content-Language fields.
[613]692   In summary, a language tag is composed of one or more parts: A primary
693   language subtag followed by a possibly empty series of subtags:
[613]695<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="language-tag"/>
[690]696  <x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in <xref target="RFC5646" x:sec="2.1"/>&gt;
699   White space is not allowed within the tag and all tags are case-insensitive.
[613]700   The name space of language subtags is administered by the IANA (see
701   <eref target=""/>).
704  <preamble>Example tags include:</preamble>
705<artwork type="example">
706  en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
[690]710   See <xref target="RFC5646"/> for further information.
715<section title="Entity" anchor="entity">
717   Request and Response messages &MAY; transfer an entity if not otherwise
718   restricted by the request method or response status code. An entity
719   consists of entity-header fields and an entity-body, although some
720   responses will only include the entity-headers.
723   In this section, both sender and recipient refer to either the client
724   or the server, depending on who sends and who receives the entity.
727<section title="Entity Header Fields" anchor="entity.header.fields">
[229]728  <x:anchor-alias value="entity-header"/>
729  <x:anchor-alias value="extension-header"/>
731   Entity-header fields define metainformation about the entity-body or,
732   if no body is present, about the resource identified by the request.
734<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="entity-header"/><iref primary="true" item="Grammar" subitem="extension-header"/>
[232]735  <x:ref>entity-header</x:ref>  = <x:ref>Content-Encoding</x:ref>         ; <xref target="header.content-encoding"/>
[334]736                 / <x:ref>Content-Language</x:ref>         ; <xref target="header.content-language"/>
737                 / <x:ref>Content-Length</x:ref>           ; &header-content-length;
738                 / <x:ref>Content-Location</x:ref>         ; <xref target="header.content-location"/>
739                 / <x:ref>Content-MD5</x:ref>              ; <xref target="header.content-md5"/>
740                 / <x:ref>Content-Range</x:ref>            ; &header-content-range;
741                 / <x:ref>Content-Type</x:ref>             ; <xref target="header.content-type"/>
742                 / <x:ref>Expires</x:ref>                  ; &header-expires;
743                 / <x:ref>Last-Modified</x:ref>            ; &header-last-modified;
744                 / <x:ref>extension-header</x:ref>
[647]746  <x:ref>extension-header</x:ref> = <x:ref>header-field</x:ref>
749   The extension-header mechanism allows additional entity-header fields
750   to be defined without changing the protocol, but these fields cannot
751   be assumed to be recognizable by the recipient. Unrecognized header
752   fields &SHOULD; be ignored by the recipient and &MUST; be forwarded by
753   transparent proxies.
757<section title="Entity Body" anchor="entity.body">
[229]758  <x:anchor-alias value="entity-body"/>
760   The entity-body (if any) sent with an HTTP request or response is in
761   a format and encoding defined by the entity-header fields.
763<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="entity-body"/>
[229]764  <x:ref>entity-body</x:ref>    = *<x:ref>OCTET</x:ref>
767   An entity-body is only present in a message when a message-body is
[29]768   present, as described in &message-body;. The entity-body is obtained
[8]769   from the message-body by decoding any Transfer-Encoding that might
770   have been applied to ensure safe and proper transfer of the message.
773<section title="Type" anchor="type">
775   When an entity-body is included with a message, the data type of that
776   body is determined via the header fields Content-Type and Content-Encoding.
777   These define a two-layer, ordered encoding model:
779<figure><artwork type="example">
[458]780  entity-body := Content-Encoding( Content-Type( data ) )
[592]783   Content-Type specifies the media type of the underlying data. Any HTTP/1.1
784   message containing an entity-body &SHOULD; include a Content-Type header
785   field defining the media type of that body, unless that information is
[831]786   unknown.
789   If the Content-Type header field is not present, it indicates that
[592]790   the sender does not know the media type of the data; recipients &MAY;
791   either assume that it is "application/octet-stream" (<xref target="RFC2046" x:fmt="," x:sec="4.5.1"/>)
792   or examine the content to determine its type.
[831]795   In practice, currently-deployed servers sometimes provide a Content-Type
796   header which does not correctly convey the intended interpretation of the
797   content sent, with the result that some clients will examine the response
798   body's content and override the specified type.
801   Client that do so risk drawing incorrect conclusions, which may expose
802   additional security risks (e.g., "privilege escalation"). Implementers are
803   encouraged to provide a means of disabling such "content sniffing" when it
804   is used.
[8]807   Content-Encoding may be used to indicate any additional content
808   codings applied to the data, usually for the purpose of data
[592]809   compression, that are a property of the requested resource.  There is
[8]810   no default encoding.
817<section title="Content Negotiation" anchor="content.negotiation">
[745]819   HTTP responses include a representation which contains information for
820   interpretation, whether by a human user or for further processing.
821   Often, the server has different ways of representing the
822   same information; for example, in different formats, languages,
823   or using different character encodings.
[745]826   HTTP clients and their users might have different or variable
827   capabilities, characteristics or preferences which would influence
828   which representation, among those available from the server,
829   would be best for the server to deliver. For this reason, HTTP
830   provides mechanisms for "content negotiation" -- a process of
831   allowing selection of a representation of a given resource,
832   when more than one is available.
[745]835   This specification defines two patterns of content negotiation;
836   "server-driven", where the server selects the representation based
837   upon the client's stated preferences, and "agent-driven" negotiation,
838   where the server provides a list of representations for the client to
839   choose from, based upon their metadata. In addition,  there are
840   other patterns: some applications use an "active content" pattern,
841   where the server returns active content which runs on the client
842   and, based on client available parameters, selects additional
843   resources to invoke. "Transparent Content Negotiation" (<xref target="RFC2295"/>)
844   has also been proposed.
847   These patterns are all widely used, and have trade-offs in applicability
848   and practicality. In particular, when the number of preferences or
849   capabilities to be expressed by a client are large (such as when many
850   different formats are supported by a user-agent), server-driven
851   negotiation becomes unwieldy, and may not be appropriate. Conversely,
852   when the number of representations to choose from is very large,
853   agent-driven negotiation may not be appropriate.
856   Note that in all cases, the supplier of representations has the
857   responsibility for determining which representations might be
858   considered to be the "same information".
861<section title="Server-driven Negotiation" anchor="server-driven.negotiation">
863   If the selection of the best representation for a response is made by
864   an algorithm located at the server, it is called server-driven
865   negotiation. Selection is based on the available representations of
[763]866   the response (the dimensions over which it can vary; e.g., language,
[8]867   content-coding, etc.) and the contents of particular header fields in
868   the request message or on other information pertaining to the request
869   (such as the network address of the client).
872   Server-driven negotiation is advantageous when the algorithm for
873   selecting from among the available representations is difficult to
874   describe to the user agent, or when the server desires to send its
875   "best guess" to the client along with the first response (hoping to
876   avoid the round-trip delay of a subsequent request if the "best
877   guess" is good enough for the user). In order to improve the server's
878   guess, the user agent &MAY; include request header fields (Accept,
879   Accept-Language, Accept-Encoding, etc.) which describe its
880   preferences for such a response.
883   Server-driven negotiation has disadvantages:
884  <list style="numbers">
885    <t>
886         It is impossible for the server to accurately determine what
887         might be "best" for any given user, since that would require
888         complete knowledge of both the capabilities of the user agent
889         and the intended use for the response (e.g., does the user want
890         to view it on screen or print it on paper?).
891    </t>
892    <t>
893         Having the user agent describe its capabilities in every
894         request can be both very inefficient (given that only a small
895         percentage of responses have multiple representations) and a
896         potential violation of the user's privacy.
897    </t>
898    <t>
899         It complicates the implementation of an origin server and the
900         algorithms for generating responses to a request.
901    </t>
902    <t>
903         It may limit a public cache's ability to use the same response
904         for multiple user's requests.
905    </t>
906  </list>
909   HTTP/1.1 includes the following request-header fields for enabling
910   server-driven negotiation through description of user agent
911   capabilities and user preferences: Accept (<xref target="header.accept"/>), Accept-Charset
912   (<xref target="header.accept-charset"/>), Accept-Encoding (<xref target="header.accept-encoding"/>), Accept-Language
[745]913   (<xref target="header.accept-language"/>), and User-Agent (&header-user-agent;).
914   However, an origin server is not limited to these dimensions and &MAY; vary
915   the response based on any aspect of the request, including information
[8]916   outside the request-header fields or within extension header fields
917   not defined by this specification.
920  <t>
921    <x:h>Note:</x:h> In practice, User-Agent based negotiation is fragile,
922    because new clients might not be recognized.
923  </t>
[115]926   The Vary header field (&header-vary;) can be used to express the parameters the
[8]927   server uses to select a representation that is subject to server-driven
[29]928   negotiation.
932<section title="Agent-driven Negotiation" anchor="agent-driven.negotiation">
934   With agent-driven negotiation, selection of the best representation
935   for a response is performed by the user agent after receiving an
936   initial response from the origin server. Selection is based on a list
937   of the available representations of the response included within the
938   header fields or entity-body of the initial response, with each
939   representation identified by its own URI. Selection from among the
940   representations may be performed automatically (if the user agent is
941   capable of doing so) or manually by the user selecting from a
942   generated (possibly hypertext) menu.
945   Agent-driven negotiation is advantageous when the response would vary
946   over commonly-used dimensions (such as type, language, or encoding),
947   when the origin server is unable to determine a user agent's
948   capabilities from examining the request, and generally when public
949   caches are used to distribute server load and reduce network usage.
952   Agent-driven negotiation suffers from the disadvantage of needing a
953   second request to obtain the best alternate representation. This
954   second request is only efficient when caching is used. In addition,
955   this specification does not define any mechanism for supporting
956   automatic selection, though it also does not prevent any such
957   mechanism from being developed as an extension and used within
958   HTTP/1.1.
[745]961   This specification defines the 300 (Multiple Choices) and 406 (Not Acceptable)
[8]962   status codes for enabling agent-driven negotiation when the server is
963   unwilling or unable to provide a varying response using server-driven
964   negotiation.
[8]969<section title="Header Field Definitions" anchor="header.fields">
[117]971   This section defines the syntax and semantics of HTTP/1.1 header fields
972   related to the payload of messages.
975   For entity-header fields, both sender and recipient refer to either the
976   client or the server, depending on who sends and who receives the entity.
[8]979<section title="Accept" anchor="header.accept">
980  <iref primary="true" item="Accept header" x:for-anchor=""/>
981  <iref primary="true" item="Headers" subitem="Accept" x:for-anchor=""/>
[229]982  <x:anchor-alias value="Accept"/>
[357]983  <x:anchor-alias value="Accept-v"/>
[370]984  <x:anchor-alias value="accept-ext"/>
[229]985  <x:anchor-alias value="accept-params"/>
986  <x:anchor-alias value="media-range"/>
[698]988   The "Accept" request-header field can be used by user agents to specify
989   response media types that are acceptable. Accept headers can be used to
990   indicate that the request is specifically limited to a small set of desired
991   types, as in the case of a request for an in-line image.
[370]993<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="Accept-v"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/>
[366]994  <x:ref>Accept</x:ref>   = "Accept" ":" <x:ref>OWS</x:ref> <x:ref>Accept-v</x:ref>
[357]995  <x:ref>Accept-v</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
[229]997  <x:ref>media-range</x:ref>    = ( "*/*"
[334]998                   / ( <x:ref>type</x:ref> "/" "*" )
999                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
[370]1000                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
1001  <x:ref>accept-params</x:ref>  = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> *( <x:ref>accept-ext</x:ref> )
[376]1002  <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref>
[810]1003                   [ "=" <x:ref>word</x:ref> ]
1006   The asterisk "*" character is used to group media types into ranges,
1007   with "*/*" indicating all media types and "type/*" indicating all
1008   subtypes of that type. The media-range &MAY; include media type
1009   parameters that are applicable to that range.
1012   Each media-range &MAY; be followed by one or more accept-params,
1013   beginning with the "q" parameter for indicating a relative quality
1014   factor. The first "q" parameter (if any) separates the media-range
1015   parameter(s) from the accept-params. Quality factors allow the user
1016   or user agent to indicate the relative degree of preference for that
[457]1017   media-range, using the qvalue scale from 0 to 1 (&qvalue;). The
[8]1018   default value is q=1.
1021  <t>
1022    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
1023    parameters from Accept extension parameters is due to historical
1024    practice. Although this prevents any media type parameter named
1025    "q" from being used with a media range, such an event is believed
1026    to be unlikely given the lack of any "q" parameters in the IANA
1027    media type registry and the rare usage of any media type
1028    parameters in Accept. Future media types are discouraged from
1029    registering any parameter named "q".
1030  </t>
1033   The example
1035<figure><artwork type="example">
[357]1036  Accept: audio/*; q=0.2, audio/basic
1039   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
1040   type if it is the best available after an 80% mark-down in quality."
1043   If no Accept header field is present, then it is assumed that the
1044   client accepts all media types. If an Accept header field is present,
1045   and if the server cannot send a response which is acceptable
1046   according to the combined Accept field value, then the server &SHOULD;
[137]1047   send a 406 (Not Acceptable) response.
1050   A more elaborate example is
1052<figure><artwork type="example">
[357]1053  Accept: text/plain; q=0.5, text/html,
1054          text/x-dvi; q=0.8, text/x-c
1057   Verbally, this would be interpreted as "text/html and text/x-c are
1058   the preferred media types, but if they do not exist, then send the
1059   text/x-dvi entity, and if that does not exist, send the text/plain
1060   entity."
1063   Media ranges can be overridden by more specific media ranges or
1064   specific media types. If more than one media range applies to a given
1065   type, the most specific reference has precedence. For example,
1067<figure><artwork type="example">
[357]1068  Accept: text/*, text/html, text/html;level=1, */*
1071   have the following precedence:
[459]1072   <list style="numbers">
1073    <t>text/html;level=1</t>
1074    <t>text/html</t>
1075    <t>text/*</t>
1076    <t>*/*</t>
1077   </list>
1080   The media type quality factor associated with a given type is
1081   determined by finding the media range with the highest precedence
1082   which matches that type. For example,
1084<figure><artwork type="example">
[357]1085  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
1086          text/html;level=2;q=0.4, */*;q=0.5
1089   would cause the following values to be associated:
[459]1091<texttable align="left">
1092  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
1093  <c>text/html;level=1</c>    <c>1</c>
1094  <c>text/html</c>            <c>0.7</c>
1095  <c>text/plain</c>           <c>0.3</c>
1096  <c>image/jpeg</c>           <c>0.5</c>
1097  <c>text/html;level=2</c>    <c>0.4</c>
1098  <c>text/html;level=3</c>    <c>0.7</c>
1101      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
1102      values for certain media ranges. However, unless the user agent is
1103      a closed system which cannot interact with other rendering agents,
1104      this default set ought to be configurable by the user.
1108<section title="Accept-Charset" anchor="header.accept-charset">
1109  <iref primary="true" item="Accept-Charset header" x:for-anchor=""/>
1110  <iref primary="true" item="Headers" subitem="Accept-Charset" x:for-anchor=""/>
[229]1111  <x:anchor-alias value="Accept-Charset"/>
[357]1112  <x:anchor-alias value="Accept-Charset-v"/>
[698]1114   The "Accept-Charset" request-header field can be used by user agents to
1115   indicate what response character sets are acceptable. This field allows
[8]1116   clients capable of understanding more comprehensive or special-purpose
[698]1117   character sets to signal that capability to a server which is capable of
1118   representing documents in those character sets.
[357]1120<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/><iref primary="true" item="Grammar" subitem="Accept-Charset-v"/>
[366]1121  <x:ref>Accept-Charset</x:ref>   = "Accept-Charset" ":" <x:ref>OWS</x:ref>
[357]1122          <x:ref>Accept-Charset-v</x:ref>
[376]1123  <x:ref>Accept-Charset-v</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
1124                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
1127   Character set values are described in <xref target="character.sets"/>. Each charset &MAY;
1128   be given an associated quality value which represents the user's
1129   preference for that charset. The default value is q=1. An example is
1131<figure><artwork type="example">
[357]1132  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
1135   The special value "*", if present in the Accept-Charset field,
1136   matches every character set (including ISO-8859-1) which is not
1137   mentioned elsewhere in the Accept-Charset field. If no "*" is present
1138   in an Accept-Charset field, then all character sets not explicitly
1139   mentioned get a quality value of 0, except for ISO-8859-1, which gets
1140   a quality value of 1 if not explicitly mentioned.
1143   If no Accept-Charset header is present, the default is that any
1144   character set is acceptable. If an Accept-Charset header is present,
1145   and if the server cannot send a response which is acceptable
1146   according to the Accept-Charset header, then the server &SHOULD; send
[137]1147   an error response with the 406 (Not Acceptable) status code, though
[8]1148   the sending of an unacceptable response is also allowed.
1152<section title="Accept-Encoding" anchor="header.accept-encoding">
1153  <iref primary="true" item="Accept-Encoding header" x:for-anchor=""/>
1154  <iref primary="true" item="Headers" subitem="Accept-Encoding" x:for-anchor=""/>
[229]1155  <x:anchor-alias value="Accept-Encoding"/>
[357]1156  <x:anchor-alias value="Accept-Encoding-v"/>
[229]1157  <x:anchor-alias value="codings"/>
[698]1159   The "Accept-Encoding" request-header field can be used by user agents to
1160   indicate what response content-codings (<xref target="content.codings"/>)
1161   are acceptable in the response.
[357]1163<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="Accept-Encoding-v"/><iref primary="true" item="Grammar" subitem="codings"/>
[366]1164  <x:ref>Accept-Encoding</x:ref>    = "Accept-Encoding" ":" <x:ref>OWS</x:ref>
[357]1165                     <x:ref>Accept-Encoding-v</x:ref>
1166  <x:ref>Accept-Encoding-v</x:ref>  =
[370]1167                     #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[357]1168  <x:ref>codings</x:ref>            = ( <x:ref>content-coding</x:ref> / "*" )
[248]1171   Each codings value &MAY; be given an associated quality value which
1172   represents the preference for that encoding. The default value is q=1.
[8]1175   Examples of its use are:
1177<figure><artwork type="example">
[357]1178  Accept-Encoding: compress, gzip
1179  Accept-Encoding:
1180  Accept-Encoding: *
1181  Accept-Encoding: compress;q=0.5, gzip;q=1.0
1182  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
1185   A server tests whether a content-coding is acceptable, according to
1186   an Accept-Encoding field, using these rules:
1187  <list style="numbers">
1188      <t>If the content-coding is one of the content-codings listed in
1189         the Accept-Encoding field, then it is acceptable, unless it is
[457]1190         accompanied by a qvalue of 0. (As defined in &qvalue;, a
[8]1191         qvalue of 0 means "not acceptable.")</t>
1193      <t>The special "*" symbol in an Accept-Encoding field matches any
1194         available content-coding not explicitly listed in the header
1195         field.</t>
1197      <t>If multiple content-codings are acceptable, then the acceptable
1198         content-coding with the highest non-zero qvalue is preferred.</t>
1200      <t>The "identity" content-coding is always acceptable, unless
1201         specifically refused because the Accept-Encoding field includes
1202         "identity;q=0", or because the field includes "*;q=0" and does
1203         not explicitly include the "identity" content-coding. If the
1204         Accept-Encoding field-value is empty, then only the "identity"
1205         encoding is acceptable.</t>
1206  </list>
1209   If an Accept-Encoding field is present in a request, and if the
1210   server cannot send a response which is acceptable according to the
1211   Accept-Encoding header, then the server &SHOULD; send an error response
1212   with the 406 (Not Acceptable) status code.
1215   If no Accept-Encoding field is present in a request, the server &MAY;
1216   assume that the client will accept any content coding. In this case,
1217   if "identity" is one of the available content-codings, then the
1218   server &SHOULD; use the "identity" content-coding, unless it has
1219   additional information that a different content-coding is meaningful
1220   to the client.
1223  <t>
1224    <x:h>Note:</x:h> If the request does not include an Accept-Encoding field,
1225    and if the "identity" content-coding is unavailable, then
1226    content-codings commonly understood by HTTP/1.0 clients (i.e.,
1227    "gzip" and "compress") are preferred; some older clients
1228    improperly display messages sent with other content-codings.  The
1229    server might also make this decision based on information about
1230    the particular user-agent or client.
1231  </t>
1234  <t>
1235    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
1236    associated with content-codings. This means that qvalues will not
1237    work and are not permitted with x-gzip or x-compress.
1238  </t>
1242<section title="Accept-Language" anchor="header.accept-language">
1243  <iref primary="true" item="Accept-Language header" x:for-anchor=""/>
1244  <iref primary="true" item="Headers" subitem="Accept-Language" x:for-anchor=""/>
[229]1245  <x:anchor-alias value="Accept-Language"/>
[357]1246  <x:anchor-alias value="Accept-Language-v"/>
[229]1247  <x:anchor-alias value="language-range"/>
[698]1249   The "Accept-Language" request-header field can be used by user agents to
1250   indicate the set of natural languages that are preferred in the response.
1251   Language tags are defined in <xref target="language.tags"/>.
[357]1253<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="Accept-Language-v"/><iref primary="true" item="Grammar" subitem="language-range"/>
[366]1254  <x:ref>Accept-Language</x:ref>   = "Accept-Language" ":" <x:ref>OWS</x:ref>
[357]1255                    <x:ref>Accept-Language-v</x:ref>
1256  <x:ref>Accept-Language-v</x:ref> =
[370]1257                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
[357]1258  <x:ref>language-range</x:ref>    =
[303]1259            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
[303]1262   Each language-range can be given an associated quality value which
[8]1263   represents an estimate of the user's preference for the languages
1264   specified by that range. The quality value defaults to "q=1". For
1265   example,
1267<figure><artwork type="example">
[357]1268  Accept-Language: da, en-gb;q=0.8, en;q=0.7
1271   would mean: "I prefer Danish, but will accept British English and
[303]1272   other types of English."
[724]1273   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
[724]1276   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
1277   several matching schemes. Implementations can offer the most appropriate
1278   matching scheme for their requirements.
1281  <t>
[756]1282    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
[724]1283    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
1284    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
[563]1285  </t>
1288   It might be contrary to the privacy expectations of the user to send
1289   an Accept-Language header with the complete linguistic preferences of
1290   the user in every request. For a discussion of this issue, see
1291   <xref target=""/>.
1294   As intelligibility is highly dependent on the individual user, it is
1295   recommended that client applications make the choice of linguistic
1296   preference available to the user. If the choice is not made
1297   available, then the Accept-Language header field &MUST-NOT; be given in
1298   the request.
1301  <t>
1302    <x:h>Note:</x:h> When making the choice of linguistic preference available to
1303    the user, we remind implementors of  the fact that users are not
1304    familiar with the details of language matching as described above,
1305    and should provide appropriate guidance. As an example, users
1306    might assume that on selecting "en-gb", they will be served any
1307    kind of English document if British English is not available. A
1308    user agent might suggest in such a case to add "en" to get the
1309    best matching behavior.
1310  </t>
1314<section title="Content-Encoding" anchor="header.content-encoding">
1315  <iref primary="true" item="Content-Encoding header" x:for-anchor=""/>
1316  <iref primary="true" item="Headers" subitem="Content-Encoding" x:for-anchor=""/>
[229]1317  <x:anchor-alias value="Content-Encoding"/>
[357]1318  <x:anchor-alias value="Content-Encoding-v"/>
[698]1320   The "Content-Encoding" entity-header field indicates what content-codings
1321   have been applied to the entity-body, and thus what decoding mechanisms
1322   must be applied in order to obtain the media-type referenced by the
1323   Content-Type header field. Content-Encoding is primarily used to allow a
1324   document to be compressed without losing the identity of its underlying
1325   media type.
[357]1327<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/><iref primary="true" item="Grammar" subitem="Content-Encoding-v"/>
[366]1328  <x:ref>Content-Encoding</x:ref>   = "Content-Encoding" ":" <x:ref>OWS</x:ref> <x:ref>Content-Encoding-v</x:ref>
[357]1329  <x:ref>Content-Encoding-v</x:ref> = 1#<x:ref>content-coding</x:ref>
1332   Content codings are defined in <xref target="content.codings"/>. An example of its use is
1334<figure><artwork type="example">
[357]1335  Content-Encoding: gzip
1338   The content-coding is a characteristic of the entity identified by
[823]1339   the Effective Request URI (&effective-request-uri;). Typically, the entity-body is stored with this
[8]1340   encoding and is only decoded before rendering or analogous usage.
1341   However, a non-transparent proxy &MAY; modify the content-coding if the
1342   new coding is known to be acceptable to the recipient, unless the
1343   "no-transform" cache-control directive is present in the message.
1346   If the content-coding of an entity is not "identity", then the
1347   response &MUST; include a Content-Encoding entity-header (<xref target="header.content-encoding"/>)
1348   that lists the non-identity content-coding(s) used.
1351   If the content-coding of an entity in a request message is not
1352   acceptable to the origin server, the server &SHOULD; respond with a
1353   status code of 415 (Unsupported Media Type).
1356   If multiple encodings have been applied to an entity, the content
1357   codings &MUST; be listed in the order in which they were applied.
1358   Additional information about the encoding parameters &MAY; be provided
1359   by other entity-header fields not defined by this specification.
1363<section title="Content-Language" anchor="header.content-language">
1364  <iref primary="true" item="Content-Language header" x:for-anchor=""/>
1365  <iref primary="true" item="Headers" subitem="Content-Language" x:for-anchor=""/>
[229]1366  <x:anchor-alias value="Content-Language"/>
[357]1367  <x:anchor-alias value="Content-Language-v"/>
[697]1369   The "Content-Language" entity-header field describes the natural
[698]1370   language(s) of the intended audience for the entity. Note that this might
1371   not be equivalent to all the languages used within the entity-body.
[357]1373<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/><iref primary="true" item="Grammar" subitem="Content-Language-v"/>
[366]1374  <x:ref>Content-Language</x:ref>   = "Content-Language" ":" <x:ref>OWS</x:ref> <x:ref>Content-Language-v</x:ref>
[357]1375  <x:ref>Content-Language-v</x:ref> = 1#<x:ref>language-tag</x:ref>
1378   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
1379   Content-Language is to allow a user to identify and differentiate
1380   entities according to the user's own preferred language. Thus, if the
1381   body content is intended only for a Danish-literate audience, the
1382   appropriate field is
1384<figure><artwork type="example">
[357]1385  Content-Language: da
1388   If no Content-Language is specified, the default is that the content
1389   is intended for all language audiences. This might mean that the
1390   sender does not consider it to be specific to any natural language,
1391   or that the sender does not know for which language it is intended.
1394   Multiple languages &MAY; be listed for content that is intended for
1395   multiple audiences. For example, a rendition of the "Treaty of
1396   Waitangi," presented simultaneously in the original Maori and English
1397   versions, would call for
1399<figure><artwork type="example">
[357]1400  Content-Language: mi, en
1403   However, just because multiple languages are present within an entity
1404   does not mean that it is intended for multiple linguistic audiences.
1405   An example would be a beginner's language primer, such as "A First
1406   Lesson in Latin," which is clearly intended to be used by an
1407   English-literate audience. In this case, the Content-Language would
1408   properly only include "en".
1411   Content-Language &MAY; be applied to any media type -- it is not
1412   limited to textual documents.
1416<section title="Content-Location" anchor="header.content-location">
1417  <iref primary="true" item="Content-Location header" x:for-anchor=""/>
1418  <iref primary="true" item="Headers" subitem="Content-Location" x:for-anchor=""/>
[229]1419  <x:anchor-alias value="Content-Location"/>
[357]1420  <x:anchor-alias value="Content-Location-v"/>
[698]1422   The "Content-Location" entity-header field is used to supply a URI for the
1423   entity in the message when it is accessible from a location separate from
1424   the requested resource's URI.
1427   A server &SHOULD; provide a Content-Location for the variant corresponding
1428   to the response entity, especially in the case where a resource has multiple
1429   entities associated with it, and those entities actually have separate
1430   locations by which they might be individually accessed, the server &SHOULD;
1431   provide a Content-Location for the particular variant which is returned.
[357]1433<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/><iref primary="true" item="Grammar" subitem="Content-Location-v"/>
[366]1434  <x:ref>Content-Location</x:ref>   = "Content-Location" ":" <x:ref>OWS</x:ref>
[357]1435                    <x:ref>Content-Location-v</x:ref>
1436  <x:ref>Content-Location-v</x:ref> =
[391]1437                    <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
[823]1440   The Content-Location value is not a replacement for the Effective
1441   Request URI (&effective-request-uri;); it is only a statement of the location of the resource
[8]1442   corresponding to this particular entity at the time of the request.
[823]1443   Future requests &MAY; may be addressed to the Content-Location URI
[8]1444   if the desire is to identify the source of that particular
1445   entity.
[716]1448   &response-representation; describes how clients may process the Content-Location header field.
[8]1451   A cache cannot assume that an entity with a Content-Location
1452   different from the URI used to retrieve it can be used to respond to
1453   later requests on that Content-Location URI. However, the Content-Location
1454   can be used to differentiate between multiple entities
[115]1455   retrieved from a single requested resource, as described in &caching-neg-resp;.
1458   If the Content-Location is a relative URI, the relative URI is
[823]1459   interpreted relative to the Effective Request URI.
[577]1462   The meaning of the Content-Location header in requests is
[8]1463   undefined; servers are free to ignore it in those cases.
1467<section title="Content-MD5" anchor="header.content-md5">
1468  <iref primary="true" item="Content-MD5 header" x:for-anchor=""/>
1469  <iref primary="true" item="Headers" subitem="Content-MD5" x:for-anchor=""/>
[229]1470  <x:anchor-alias value="Content-MD5"/>
[357]1471  <x:anchor-alias value="Content-MD5-v"/>
[697]1473   The "Content-MD5" entity-header field, as defined in <xref target="RFC1864"/>, is
[699]1474   an MD5 digest of the entity-body that provides an end-to-end message
1475   integrity check (MIC) of the entity-body. Note that a MIC is good for
1476   detecting accidental modification of the entity-body in transit, but is not
1477   proof against malicious attacks.
[357]1479<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-MD5"/><iref primary="true" item="Grammar" subitem="Content-MD5-v"/>
[366]1480  <x:ref>Content-MD5</x:ref>   = "Content-MD5" ":" <x:ref>OWS</x:ref> <x:ref>Content-MD5-v</x:ref>
[357]1481  <x:ref>Content-MD5-v</x:ref> = &lt;base64 of 128 bit MD5 digest as per <xref target="RFC1864"/>&gt;
1484   The Content-MD5 header field &MAY; be generated by an origin server or
1485   client to function as an integrity check of the entity-body. Only
1486   origin servers or clients &MAY; generate the Content-MD5 header field;
1487   proxies and gateways &MUST-NOT; generate it, as this would defeat its
1488   value as an end-to-end integrity check. Any recipient of the entity-body,
1489   including gateways and proxies, &MAY; check that the digest value
1490   in this header field matches that of the entity-body as received.
1493   The MD5 digest is computed based on the content of the entity-body,
1494   including any content-coding that has been applied, but not including
1495   any transfer-encoding applied to the message-body. If the message is
1496   received with a transfer-encoding, that encoding &MUST; be removed
1497   prior to checking the Content-MD5 value against the received entity.
1500   This has the result that the digest is computed on the octets of the
1501   entity-body exactly as, and in the order that, they would be sent if
1502   no transfer-encoding were being applied.
1505   HTTP extends RFC 1864 to permit the digest to be computed for MIME
1506   composite media-types (e.g., multipart/* and message/rfc822), but
1507   this does not change how the digest is computed as defined in the
1508   preceding paragraph.
1511   There are several consequences of this. The entity-body for composite
1512   types &MAY; contain many body-parts, each with its own MIME and HTTP
1513   headers (including Content-MD5, Content-Transfer-Encoding, and
1514   Content-Encoding headers). If a body-part has a Content-Transfer-Encoding
1515   or Content-Encoding header, it is assumed that the content
1516   of the body-part has had the encoding applied, and the body-part is
1517   included in the Content-MD5 digest as is -- i.e., after the
1518   application. The Transfer-Encoding header field is not allowed within
1519   body-parts.
1522   Conversion of all line breaks to CRLF &MUST-NOT; be done before
1523   computing or checking the digest: the line break convention used in
1524   the text actually transmitted &MUST; be left unaltered when computing
1525   the digest.
1528  <t>
[756]1529    <x:h>Note:</x:h> While the definition of Content-MD5 is exactly the same for
[563]1530    HTTP as in RFC 1864 for MIME entity-bodies, there are several ways
1531    in which the application of Content-MD5 to HTTP entity-bodies
1532    differs from its application to MIME entity-bodies. One is that
1533    HTTP, unlike MIME, does not use Content-Transfer-Encoding, and
1534    does use Transfer-Encoding and Content-Encoding. Another is that
1535    HTTP more frequently uses binary content types than MIME, so it is
1536    worth noting that, in such cases, the byte order used to compute
1537    the digest is the transmission byte order defined for the type.
1538    Lastly, HTTP allows transmission of text types with any of several
1539    line break conventions and not just the canonical form using CRLF.
1540  </t>
1544<section title="Content-Type" anchor="header.content-type">
1545  <iref primary="true" item="Content-Type header" x:for-anchor=""/>
1546  <iref primary="true" item="Headers" subitem="Content-Type" x:for-anchor=""/>
[229]1547  <x:anchor-alias value="Content-Type"/>
[357]1548  <x:anchor-alias value="Content-Type-v"/>
[697]1550   The "Content-Type" entity-header field indicates the media type of the
[698]1551   entity-body. In the case of responses to the HEAD method, the media type is
1552   that which would have been sent had the request been a GET.
[357]1554<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/><iref primary="true" item="Grammar" subitem="Content-Type-v"/>
[366]1555  <x:ref>Content-Type</x:ref>   = "Content-Type" ":" <x:ref>OWS</x:ref> <x:ref>Content-Type-v</x:ref>
[357]1556  <x:ref>Content-Type-v</x:ref> = <x:ref>media-type</x:ref>
1559   Media types are defined in <xref target="media.types"/>. An example of the field is
1561<figure><artwork type="example">
[357]1562  Content-Type: text/html; charset=ISO-8859-4
1565   Further discussion of methods for identifying the media type of an
1566   entity is provided in <xref target="type"/>.
[29]1572<section title="IANA Considerations" anchor="IANA.considerations">
[253]1573<section title="Message Header Registration" anchor="message.header.registration">
1575   The Message Header Registry located at <eref target=""/> should be updated
1576   with the permanent registrations below (see <xref target="RFC3864"/>):
[680]1578<?BEGININC p3-payload.iana-headers ?>
[253]1579<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]1580<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]1581   <ttcol>Header Field Name</ttcol>
1582   <ttcol>Protocol</ttcol>
1583   <ttcol>Status</ttcol>
1584   <ttcol>Reference</ttcol>
1586   <c>Accept</c>
1587   <c>http</c>
1588   <c>standard</c>
1589   <c>
1590      <xref target="header.accept"/>
1591   </c>
1592   <c>Accept-Charset</c>
1593   <c>http</c>
1594   <c>standard</c>
1595   <c>
1596      <xref target="header.accept-charset"/>
1597   </c>
1598   <c>Accept-Encoding</c>
1599   <c>http</c>
1600   <c>standard</c>
1601   <c>
1602      <xref target="header.accept-encoding"/>
1603   </c>
1604   <c>Accept-Language</c>
1605   <c>http</c>
1606   <c>standard</c>
1607   <c>
1608      <xref target="header.accept-language"/>
1609   </c>
1610   <c>Content-Disposition</c>
1611   <c>http</c>
[291]1612   <c/>
[253]1613   <c>
1614      <xref target="content-disposition"/>
1615   </c>
1616   <c>Content-Encoding</c>
1617   <c>http</c>
1618   <c>standard</c>
1619   <c>
1620      <xref target="header.content-encoding"/>
1621   </c>
1622   <c>Content-Language</c>
1623   <c>http</c>
1624   <c>standard</c>
1625   <c>
1626      <xref target="header.content-language"/>
1627   </c>
1628   <c>Content-Location</c>
1629   <c>http</c>
1630   <c>standard</c>
1631   <c>
1632      <xref target="header.content-location"/>
1633   </c>
1634   <c>Content-MD5</c>
1635   <c>http</c>
1636   <c>standard</c>
1637   <c>
1638      <xref target="header.content-md5"/>
1639   </c>
1640   <c>Content-Type</c>
1641   <c>http</c>
1642   <c>standard</c>
1643   <c>
1644      <xref target="header.content-type"/>
1645   </c>
[291]1646   <c>MIME-Version</c>
1647   <c>http</c>
1648   <c/>
1649   <c>
1650      <xref target="mime-version"/>
1651   </c>
[680]1654<?ENDINC p3-payload.iana-headers ?>
[290]1656   The change controller is: "IETF ( - Internet Engineering Task Force".
[668]1660<section title="Content Coding Registry" anchor="content.coding.registration">
1662   The registration procedure for HTTP Content Codings is now defined
[670]1663   by <xref target="content.coding.registry"/> of this document.
1666   The HTTP Content Codings Registry located at <eref target=""/>
[673]1667   should be updated with the registration below:
1669<texttable align="left" suppress-title="true" anchor="iana.content.coding.registration.table">
[670]1670   <ttcol>Name</ttcol>
[668]1671   <ttcol>Description</ttcol>
1672   <ttcol>Reference</ttcol>
1673   <c>compress</c>
1674   <c>UNIX "compress" program method</c>
1675   <c>
[673]1676      &compress-coding;
[668]1677   </c>
1678   <c>deflate</c>
[806]1679   <c>"deflate" compression mechanism (<xref target="RFC1951"/>) used inside
1680   the "zlib" data format (<xref target="RFC1950"/>)
1681   </c>
[668]1682   <c>
[673]1683      &deflate-coding;
[668]1684   </c>
1685   <c>gzip</c>
1686   <c>Same as GNU zip <xref target="RFC1952"/></c>
1687   <c>
[673]1688      &gzip-coding;
[668]1689   </c>
1690   <c>identity</c>
1691   <c>No transformation</c>
1692   <c>
1693      <xref target="content.codings"/>
1694   </c>
[8]1700<section title="Security Considerations" anchor="security.considerations">
1702   This section is meant to inform application developers, information
1703   providers, and users of the security limitations in HTTP/1.1 as
1704   described by this document. The discussion does not include
1705   definitive solutions to the problems revealed, though it does make
1706   some suggestions for reducing security risks.
1709<section title="Privacy Issues Connected to Accept Headers" anchor="">
1711   Accept request-headers can reveal information about the user to all
1712   servers which are accessed. The Accept-Language header in particular
1713   can reveal information the user would consider to be of a private
1714   nature, because the understanding of particular languages is often
1715   strongly correlated to the membership of a particular ethnic group.
1716   User agents which offer the option to configure the contents of an
1717   Accept-Language header to be sent in every request are strongly
1718   encouraged to let the configuration process include a message which
1719   makes the user aware of the loss of privacy involved.
1722   An approach that limits the loss of privacy would be for a user agent
1723   to omit the sending of Accept-Language headers by default, and to ask
1724   the user whether or not to start sending Accept-Language headers to a
1725   server if it detects, by looking for any Vary response-header fields
1726   generated by the server, that such sending could improve the quality
1727   of service.
1730   Elaborate user-customized accept header fields sent in every request,
1731   in particular if these include quality values, can be used by servers
1732   as relatively reliable and long-lived user identifiers. Such user
1733   identifiers would allow content providers to do click-trail tracking,
1734   and would allow collaborating content providers to match cross-server
1735   click-trails or form submissions of individual users. Note that for
1736   many users not behind a proxy, the network address of the host
1737   running the user agent will also serve as a long-lived user
1738   identifier. In environments where proxies are used to enhance
1739   privacy, user agents ought to be conservative in offering accept
1740   header configuration options to end users. As an extreme privacy
1741   measure, proxies could filter the accept headers in relayed requests.
1742   General purpose user agents which provide a high degree of header
1743   configurability &SHOULD; warn users about the loss of privacy which can
1744   be involved.
1748<section title="Content-Disposition Issues" anchor="content-disposition.issues">
[269]1750   <xref target="RFC2183"/>, from which the often implemented Content-Disposition
[8]1751   (see <xref target="content-disposition"/>) header in HTTP is derived, has a number of very
1752   serious security considerations. Content-Disposition is not part of
1753   the HTTP standard, but since it is widely implemented, we are
[269]1754   documenting its use and risks for implementors. See <xref target="RFC2183" x:fmt="of" x:sec="5"/>
1755   for details.
1761<section title="Acknowledgments" anchor="ack">
[119]1766<references title="Normative References">
[121]1768<reference anchor="ISO-8859-1">
1769  <front>
1770    <title>
1771     Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1
1772    </title>
1773    <author>
1774      <organization>International Organization for Standardization</organization>
1775    </author>
1776    <date year="1998"/>
1777  </front>
1778  <seriesInfo name="ISO/IEC" value="8859-1:1998"/>
[31]1781<reference anchor="Part1">
[119]1782  <front>
1783    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
1784    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1785      <organization abbrev="Day Software">Day Software</organization>
1786      <address><email></email></address>
1787    </author>
1788    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1789      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1790      <address><email></email></address>
[119]1791    </author>
1792    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1793      <organization abbrev="HP">Hewlett-Packard Company</organization>
1794      <address><email></email></address>
1795    </author>
1796    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1797      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1798      <address><email></email></address>
1799    </author>
1800    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1801      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1802      <address><email></email></address>
1803    </author>
1804    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1805      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1806      <address><email></email></address>
1807    </author>
1808    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1809      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1810      <address><email></email></address>
1811    </author>
1812    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1813      <organization abbrev="W3C">World Wide Web Consortium</organization>
1814      <address><email></email></address>
1815    </author>
1816    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1817      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1818      <address><email></email></address>
1819    </author>
1820    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1821  </front>
1822  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
1823  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
1826<reference anchor="Part2">
[119]1827  <front>
1828    <title abbrev="HTTP/1.1">HTTP/1.1, part 2: Message Semantics</title>
1829    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1830      <organization abbrev="Day Software">Day Software</organization>
1831      <address><email></email></address>
1832    </author>
1833    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1834      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1835      <address><email></email></address>
[119]1836    </author>
1837    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1838      <organization abbrev="HP">Hewlett-Packard Company</organization>
1839      <address><email></email></address>
1840    </author>
1841    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1842      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1843      <address><email></email></address>
1844    </author>
1845    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1846      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1847      <address><email></email></address>
1848    </author>
1849    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1850      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1851      <address><email></email></address>
1852    </author>
1853    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1854      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1855      <address><email></email></address>
1856    </author>
1857    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1858      <organization abbrev="W3C">World Wide Web Consortium</organization>
1859      <address><email></email></address>
1860    </author>
1861    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1862      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1863      <address><email></email></address>
1864    </author>
1865    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1866  </front>
1867  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"/>
1868  <x:source href="p2-semantics.xml" basename="p2-semantics"/>
1871<reference anchor="Part4">
[119]1872  <front>
1873    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
1874    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1875      <organization abbrev="Day Software">Day Software</organization>
1876      <address><email></email></address>
1877    </author>
1878    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1879      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1880      <address><email></email></address>
[119]1881    </author>
1882    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1883      <organization abbrev="HP">Hewlett-Packard Company</organization>
1884      <address><email></email></address>
1885    </author>
1886    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1887      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1888      <address><email></email></address>
1889    </author>
1890    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1891      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1892      <address><email></email></address>
1893    </author>
1894    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1895      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1896      <address><email></email></address>
1897    </author>
1898    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1899      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1900      <address><email></email></address>
1901    </author>
1902    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1903      <organization abbrev="W3C">World Wide Web Consortium</organization>
1904      <address><email></email></address>
1905    </author>
1906    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1907      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1908      <address><email></email></address>
1909    </author>
1910    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1911  </front>
1912  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
1913  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
1916<reference anchor="Part5">
[119]1917  <front>
1918    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
1919    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1920      <organization abbrev="Day Software">Day Software</organization>
1921      <address><email></email></address>
1922    </author>
1923    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1924      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1925      <address><email></email></address>
[119]1926    </author>
1927    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1928      <organization abbrev="HP">Hewlett-Packard Company</organization>
1929      <address><email></email></address>
1930    </author>
1931    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1932      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1933      <address><email></email></address>
1934    </author>
1935    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1936      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1937      <address><email></email></address>
1938    </author>
1939    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1940      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1941      <address><email></email></address>
1942    </author>
1943    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1944      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1945      <address><email></email></address>
1946    </author>
1947    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1948      <organization abbrev="W3C">World Wide Web Consortium</organization>
1949      <address><email></email></address>
1950    </author>
1951    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
1952      <organization abbrev="greenbytes">greenbytes GmbH</organization>
1953      <address><email></email></address>
1954    </author>
1955    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
1956  </front>
1957  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
1958  <x:source href="p5-range.xml" basename="p5-range"/>
1961<reference anchor="Part6">
[119]1962  <front>
1963    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
1964    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
1965      <organization abbrev="Day Software">Day Software</organization>
1966      <address><email></email></address>
1967    </author>
1968    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]1969      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
1970      <address><email></email></address>
[119]1971    </author>
1972    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
1973      <organization abbrev="HP">Hewlett-Packard Company</organization>
1974      <address><email></email></address>
1975    </author>
1976    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
1977      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1978      <address><email></email></address>
1979    </author>
1980    <author initials="L." surname="Masinter" fullname="Larry Masinter">
1981      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
1982      <address><email></email></address>
1983    </author>
1984    <author initials="P." surname="Leach" fullname="Paul J. Leach">
1985      <organization abbrev="Microsoft">Microsoft Corporation</organization>
1986      <address><email></email></address>
1987    </author>
1988    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
1989      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
1990      <address><email></email></address>
1991    </author>
1992    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
1993      <organization abbrev="W3C">World Wide Web Consortium</organization>
1994      <address><email></email></address>
1995    </author>
[601]1996    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
1997      <address><email></email></address>
1998    </author>
[119]1999    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2000      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2001      <address><email></email></address>
2002    </author>
2003    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2004  </front>
2005  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2006  <x:source href="p6-cache.xml" basename="p6-cache"/>
[131]2009<reference anchor="RFC1864">
2010  <front>
2011    <title abbrev="Content-MD5 Header Field">The Content-MD5 Header Field</title>
2012    <author initials="J." surname="Myers" fullname="John G. Myers">
2013      <organization>Carnegie Mellon University</organization>
2014      <address><email></email></address>
2015    </author>
2016    <author initials="M." surname="Rose" fullname="Marshall T. Rose">
2017      <organization>Dover Beach Consulting, Inc.</organization>
2018      <address><email></email></address>
2019    </author>
2020    <date month="October" year="1995"/>
2021  </front>
2022  <seriesInfo name="RFC" value="1864"/>
[122]2025<reference anchor="RFC1950">
2026  <front>
2027    <title>ZLIB Compressed Data Format Specification version 3.3</title>
2028    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2029      <organization>Aladdin Enterprises</organization>
2030      <address><email></email></address>
2031    </author>
[713]2032    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly"/>
[122]2033    <date month="May" year="1996"/>
2034  </front>
2035  <seriesInfo name="RFC" value="1950"/>
2036  <annotation>
[277]2037    RFC 1950 is an Informational RFC, thus it may be less stable than
[122]2038    this specification. On the other hand, this downward reference was
[277]2039    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2040    therefore it is unlikely to cause problems in practice. See also
2041    <xref target="BCP97"/>.
[122]2042  </annotation>
[806]2045<reference anchor="RFC1951">
2046  <front>
2047    <title>DEFLATE Compressed Data Format Specification version 1.3</title>
2048    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2049      <organization>Aladdin Enterprises</organization>
2050      <address><email></email></address>
2051    </author>
2052    <date month="May" year="1996"/>
2053  </front>
2054  <seriesInfo name="RFC" value="1951"/>
2055  <annotation>
2056    RFC 1951 is an Informational RFC, thus it may be less stable than
2057    this specification. On the other hand, this downward reference was
2058    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2059    therefore it is unlikely to cause problems in practice. See also
2060    <xref target="BCP97"/>.
2061  </annotation>
[122]2064<reference anchor="RFC1952">
2065  <front>
2066    <title>GZIP file format specification version 4.3</title>
2067    <author initials="P." surname="Deutsch" fullname="L. Peter Deutsch">
2068      <organization>Aladdin Enterprises</organization>
2069      <address><email></email></address>
2070    </author>
2071    <author initials="J-L." surname="Gailly" fullname="Jean-Loup Gailly">
2072      <address><email></email></address>
2073    </author>
2074    <author initials="M." surname="Adler" fullname="Mark Adler">
2075      <address><email></email></address>
2076    </author>
2077    <author initials="L.P." surname="Deutsch" fullname="L. Peter Deutsch">
2078      <address><email></email></address>
2079    </author>
2080    <author initials="G." surname="Randers-Pehrson" fullname="Glenn Randers-Pehrson">
2081      <address><email></email></address>
2082    </author>
2083    <date month="May" year="1996"/>
2084  </front>
2085  <seriesInfo name="RFC" value="1952"/>
2086  <annotation>
[277]2087    RFC 1952 is an Informational RFC, thus it may be less stable than
[122]2088    this specification. On the other hand, this downward reference was
[277]2089    present since the publication of RFC 2068 in 1997 (<xref target="RFC2068"/>),
2090    therefore it is unlikely to cause problems in practice. See also
2091    <xref target="BCP97"/>.
[122]2092  </annotation>
[131]2095<reference anchor="RFC2045">
2096  <front>
2097    <title abbrev="Internet Message Bodies">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</title>
2098    <author initials="N." surname="Freed" fullname="Ned Freed">
2099      <organization>Innosoft International, Inc.</organization>
2100      <address><email></email></address>
2101    </author>
2102    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2103      <organization>First Virtual Holdings</organization>
2104      <address><email></email></address>
2105    </author>
2106    <date month="November" year="1996"/>
2107  </front>
2108  <seriesInfo name="RFC" value="2045"/>
2111<reference anchor="RFC2046">
2112  <front>
2113    <title abbrev="Media Types">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types</title>
2114    <author initials="N." surname="Freed" fullname="Ned Freed">
2115      <organization>Innosoft International, Inc.</organization>
2116      <address><email></email></address>
2117    </author>
2118    <author initials="N." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2119      <organization>First Virtual Holdings</organization>
2120      <address><email></email></address>
2121    </author>
2122    <date month="November" year="1996"/>
2123  </front>
2124  <seriesInfo name="RFC" value="2046"/>
[119]2127<reference anchor="RFC2119">
2128  <front>
2129    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2130    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2131      <organization>Harvard University</organization>
2132      <address><email></email></address>
2133    </author>
2134    <date month="March" year="1997"/>
2135  </front>
2136  <seriesInfo name="BCP" value="14"/>
2137  <seriesInfo name="RFC" value="2119"/>
[303]2140<reference anchor='RFC4647'>
2141  <front>
2142    <title>Matching of Language Tags</title>
2143    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role="editor">
2144      <organization>Yahoo! Inc.</organization>
2145      <address><email></email></address>
2146    </author>
2147    <author initials='M.' surname='Davis' fullname='Mark Davis' role="editor">
2148      <organization>Google</organization>
2149      <address><email></email></address>
2150    </author>
2151    <date year='2006' month='September' />
2152  </front>
2153  <seriesInfo name='BCP' value='47' />
2154  <seriesInfo name='RFC' value='4647' />
[425]2157<reference anchor="RFC5234">
2158  <front>
2159    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2160    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2161      <organization>Brandenburg InternetWorking</organization>
2162      <address>
[728]2163        <email></email>
2164      </address> 
[425]2165    </author>
2166    <author initials="P." surname="Overell" fullname="Paul Overell">
2167      <organization>THUS plc.</organization>
2168      <address>
[728]2169        <email></email>
2170      </address>
[425]2171    </author>
2172    <date month="January" year="2008"/>
2173  </front>
2174  <seriesInfo name="STD" value="68"/>
2175  <seriesInfo name="RFC" value="5234"/>
[690]2178<reference anchor='RFC5646'>
[613]2179  <front>
2180    <title>Tags for Identifying Languages</title>
2181    <author initials='A.' surname='Phillips' fullname='Addison Phillips' role='editor'>
2182      <organization>Lab126</organization>
2183      <address><email></email></address>
2184    </author>
2185    <author initials='M.' surname='Davis' fullname='Mark Davis' role='editor'>
2186      <organization>Google</organization>
2187      <address><email></email></address>
2188    </author>
[690]2189    <date month='September' year='2009' />
[613]2190  </front>
[690]2191  <seriesInfo name='BCP' value='47' />
2192  <seriesInfo name='RFC' value='5646' />
2197<references title="Informative References">
[129]2199<reference anchor="RFC1945">
2200  <front>
2201    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2202    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2203      <organization>MIT, Laboratory for Computer Science</organization>
2204      <address><email></email></address>
2205    </author>
2206    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2207      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2208      <address><email></email></address>
2209    </author>
2210    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2211      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2212      <address><email></email></address>
2213    </author>
2214    <date month="May" year="1996"/>
2215  </front>
2216  <seriesInfo name="RFC" value="1945"/>
2219<reference anchor="RFC2049">
2220  <front>
2221    <title abbrev="MIME Conformance">Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples</title>
2222    <author initials="N." surname="Freed" fullname="Ned Freed">
2223      <organization>Innosoft International, Inc.</organization>
2224      <address><email></email></address>
2225    </author>
2226    <author initials="N.S." surname="Borenstein" fullname="Nathaniel S. Borenstein">
2227      <organization>First Virtual Holdings</organization>
2228      <address><email></email></address>
2229    </author>
2230    <date month="November" year="1996"/>
2231  </front>
2232  <seriesInfo name="RFC" value="2049"/>
[133]2235<reference anchor="RFC2068">
2236  <front>
2237    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2238    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2239      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2240      <address><email></email></address>
2241    </author>
2242    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2243      <organization>MIT Laboratory for Computer Science</organization>
2244      <address><email></email></address>
2245    </author>
2246    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2247      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2248      <address><email></email></address>
2249    </author>
2250    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2251      <organization>MIT Laboratory for Computer Science</organization>
2252      <address><email></email></address>
2253    </author>
2254    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2255      <organization>MIT Laboratory for Computer Science</organization>
2256      <address><email></email></address>
2257    </author>
2258    <date month="January" year="1997"/>
2259  </front>
2260  <seriesInfo name="RFC" value="2068"/>
[129]2263<reference anchor="RFC2076">
2264  <front>
2265    <title abbrev="Internet Message Headers">Common Internet Message Headers</title>
2266    <author initials="J." surname="Palme" fullname="Jacob Palme">
2267      <organization>Stockholm University/KTH</organization>
2268      <address><email></email></address>
2269    </author>
2270    <date month="February" year="1997"/>
2271  </front>
2272  <seriesInfo name="RFC" value="2076"/>
2275<reference anchor="RFC2183">
2276  <front>
2277    <title abbrev="Content-Disposition">Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field</title>
2278    <author initials="R." surname="Troost" fullname="Rens Troost">
2279      <organization>New Century Systems</organization>
2280      <address><email></email></address>
2281    </author>
2282    <author initials="S." surname="Dorner" fullname="Steve Dorner">
2283      <organization>QUALCOMM Incorporated</organization>
2284      <address><email></email></address>
2285    </author>
2286    <author initials="K." surname="Moore" fullname="Keith Moore">
2287      <organization>Department of Computer Science</organization>
2288      <address><email></email></address>
2289    </author>
2290    <date month="August" year="1997"/>
2291  </front>
2292  <seriesInfo name="RFC" value="2183"/>
2295<reference anchor="RFC2277">
2296  <front>
2297    <title abbrev="Charset Policy">IETF Policy on Character Sets and Languages</title>
2298    <author initials="H.T." surname="Alvestrand" fullname="Harald Tveit Alvestrand">
2299      <organization>UNINETT</organization>
2300      <address><email></email></address>
2301    </author>
2302    <date month="January" year="1998"/>
2303  </front>
2304  <seriesInfo name="BCP" value="18"/>
2305  <seriesInfo name="RFC" value="2277"/>
[745]2308<reference anchor='RFC2295'>
2309  <front>
2310    <title abbrev='HTTP Content Negotiation'>Transparent Content Negotiation in HTTP</title>
2311    <author initials='K.' surname='Holtman' fullname='Koen Holtman'>
2312      <organization>Technische Universiteit Eindhoven</organization>
2313      <address>
2314        <email></email>
2315      </address>
2316    </author>
2317    <author initials='A.H.' surname='Mutz' fullname='Andrew H. Mutz'>
2318      <organization>Hewlett-Packard Company</organization>
2319      <address>
2320        <email></email>
2321      </address>
2322    </author>
2323    <date year='1998' month='March'/>
2324  </front>
2325  <seriesInfo name='RFC' value='2295'/>
[129]2328<reference anchor="RFC2388">
2329  <front>
2330    <title abbrev="multipart/form-data">Returning Values from Forms:  multipart/form-data</title>
2331    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2332      <organization>Xerox Palo Alto Research Center</organization>
2333      <address><email></email></address>
2334    </author>
2335    <date year="1998" month="August"/>
2336  </front>
2337  <seriesInfo name="RFC" value="2388"/>
2340<reference anchor="RFC2557">
2341  <front>
2342    <title abbrev="MIME Encapsulation of Aggregate Documents">MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)</title>
2343    <author initials="F." surname="Palme" fullname="Jacob Palme">
2344      <organization>Stockholm University and KTH</organization>
2345      <address><email></email></address>
2346    </author>
2347    <author initials="A." surname="Hopmann" fullname="Alex Hopmann">
2348      <organization>Microsoft Corporation</organization>
2349      <address><email></email></address>
2350    </author>
2351    <author initials="N." surname="Shelness" fullname="Nick Shelness">
2352      <organization>Lotus Development Corporation</organization>
2353      <address><email></email></address>
2354    </author>
2355    <author initials="E." surname="Stefferud" fullname="Einar Stefferud">
2356      <address><email></email></address>
2357    </author>
2358    <date year="1999" month="March"/>
2359  </front>
2360  <seriesInfo name="RFC" value="2557"/>
[119]2363<reference anchor="RFC2616">
2364  <front>
2365    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2366    <author initials="R." surname="Fielding" fullname="R. Fielding">
2367      <organization>University of California, Irvine</organization>
2368      <address><email></email></address>
2369    </author>
2370    <author initials="J." surname="Gettys" fullname="J. Gettys">
2371      <organization>W3C</organization>
2372      <address><email></email></address>
2373    </author>
2374    <author initials="J." surname="Mogul" fullname="J. Mogul">
2375      <organization>Compaq Computer Corporation</organization>
2376      <address><email></email></address>
2377    </author>
2378    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2379      <organization>MIT Laboratory for Computer Science</organization>
2380      <address><email></email></address>
2381    </author>
2382    <author initials="L." surname="Masinter" fullname="L. Masinter">
2383      <organization>Xerox Corporation</organization>
2384      <address><email></email></address>
2385    </author>
2386    <author initials="P." surname="Leach" fullname="P. Leach">
2387      <organization>Microsoft Corporation</organization>
2388      <address><email></email></address>
2389    </author>
2390    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2391      <organization>W3C</organization>
2392      <address><email></email></address>
2393    </author>
2394    <date month="June" year="1999"/>
2395  </front>
2396  <seriesInfo name="RFC" value="2616"/>
[129]2399<reference anchor="RFC3629">
2400  <front>
2401    <title>UTF-8, a transformation format of ISO 10646</title>
2402    <author initials="F." surname="Yergeau" fullname="F. Yergeau">
2403      <organization>Alis Technologies</organization>
2404      <address><email></email></address>
2405    </author>
2406    <date month="November" year="2003"/>
2407  </front>
2408  <seriesInfo name="RFC" value="3629"/>
2409  <seriesInfo name="STD" value="63"/>
[253]2412<reference anchor='RFC3864'>
2413  <front>
2414    <title>Registration Procedures for Message Header Fields</title>
2415    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2416      <organization>Nine by Nine</organization>
2417      <address><email></email></address>
2418    </author>
2419    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2420      <organization>BEA Systems</organization>
2421      <address><email></email></address>
2422    </author>
2423    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2424      <organization>HP Labs</organization>
2425      <address><email></email></address>
2426    </author>
2427    <date year='2004' month='September' />
2428  </front>
2429  <seriesInfo name='BCP' value='90' />
2430  <seriesInfo name='RFC' value='3864' />
[200]2433<reference anchor="RFC4288">
2434  <front>
2435    <title>Media Type Specifications and Registration Procedures</title>
2436    <author initials="N." surname="Freed" fullname="N. Freed">
2437      <organization>Sun Microsystems</organization>
2438      <address>
2439        <email></email>
2440      </address>
2441    </author>
2442    <author initials="J." surname="Klensin" fullname="J. Klensin">
2443      <address>
2444        <email></email>
2445      </address>
2446    </author>
2447    <date year="2005" month="December"/>
2448  </front>
2449  <seriesInfo name="BCP" value="13"/>
2450  <seriesInfo name="RFC" value="4288"/>
[670]2453<reference anchor='RFC5226'>
2454  <front>
2455    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2456    <author initials='T.' surname='Narten' fullname='T. Narten'>
2457      <organization>IBM</organization>
2458      <address><email></email></address>
2459    </author>
2460    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
2461      <organization>Google</organization>
2462      <address><email></email></address>
2463    </author>
2464    <date year='2008' month='May' />
2465  </front>
2466  <seriesInfo name='BCP' value='26' />
2467  <seriesInfo name='RFC' value='5226' />
[327]2470<reference anchor="RFC5322">
2471  <front>
2472    <title>Internet Message Format</title>
2473    <author initials="P." surname="Resnick" fullname="P. Resnick">
2474      <organization>Qualcomm Incorporated</organization>
2475    </author>
2476    <date year="2008" month="October"/>
2477  </front>
2478  <seriesInfo name="RFC" value="5322"/>
[277]2481<reference anchor='BCP97'>
2482  <front>
2483    <title>Handling Normative References to Standards-Track Documents</title>
2484    <author initials='J.' surname='Klensin' fullname='J. Klensin'>
2485      <address>
2486        <email></email>
2487      </address>
2488    </author>
2489    <author initials='S.' surname='Hartman' fullname='S. Hartman'>
2490      <organization>MIT</organization>
2491      <address>
2492        <email></email>
2493      </address>
2494    </author>
2495    <date year='2007' month='June' />
2496  </front>
2497  <seriesInfo name='BCP' value='97' />
2498  <seriesInfo name='RFC' value='4897' />
[8]2504<section title="Differences Between HTTP Entities and RFC 2045 Entities" anchor="differences.between.http.entities.and.rfc.2045.entities">
[327]2506   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
[8]2507   allow entities to be transmitted in an open variety of
2508   representations and with extensible mechanisms. However, RFC 2045
2509   discusses mail, and HTTP has a few features that are different from
2510   those described in RFC 2045. These differences were carefully chosen
2511   to optimize performance over binary connections, to allow greater
2512   freedom in the use of new media types, to make date comparisons
2513   easier, and to acknowledge the practice of some early HTTP servers
2514   and clients.
2517   This appendix describes specific areas where HTTP differs from RFC
2518   2045. Proxies and gateways to strict MIME environments &SHOULD; be
2519   aware of these differences and provide the appropriate conversions
2520   where necessary. Proxies and gateways from MIME environments to HTTP
2521   also need to be aware of the differences because some conversions
2522   might be required.
[8]2525<section title="MIME-Version" anchor="mime-version">
[291]2526  <iref primary="true" item="MIME-Version header" x:for-anchor=""/>
2527  <iref primary="true" item="Headers" subitem="MIME-Version" x:for-anchor=""/>
[229]2528  <x:anchor-alias value="MIME-Version"/>
[357]2529  <x:anchor-alias value="MIME-Version-v"/>
2531   HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages &MAY;
2532   include a single MIME-Version general-header field to indicate what
2533   version of the MIME protocol was used to construct the message. Use
2534   of the MIME-Version header field indicates that the message is in
[115]2535   full compliance with the MIME protocol (as defined in <xref target="RFC2045"/>).
[8]2536   Proxies/gateways are responsible for ensuring full compliance (where
2537   possible) when exporting HTTP messages to strict MIME environments.
[357]2539<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="MIME-Version"/><iref primary="true" item="Grammar" subitem="MIME-Version-v"/>
[366]2540  <x:ref>MIME-Version</x:ref>   = "MIME-Version" ":" <x:ref>OWS</x:ref> <x:ref>MIME-Version-v</x:ref>
[357]2541  <x:ref>MIME-Version-v</x:ref> = 1*<x:ref>DIGIT</x:ref> "." 1*<x:ref>DIGIT</x:ref>
2544   MIME version "1.0" is the default for use in HTTP/1.1. However,
2545   HTTP/1.1 message parsing and semantics are defined by this document
2546   and not the MIME specification.
2550<section title="Conversion to Canonical Form" anchor="">
[97]2552   <xref target="RFC2045"/> requires that an Internet mail entity be converted to
[115]2553   canonical form prior to being transferred, as described in <xref target="RFC2049" x:fmt="of" x:sec="4"/>.
[97]2554   <xref target="canonicalization.and.text.defaults"/> of this document describes the forms
[8]2555   allowed for subtypes of the "text" media type when transmitted over
[97]2556   HTTP. <xref target="RFC2046"/> requires that content with a type of "text" represent
[8]2557   line breaks as CRLF and forbids the use of CR or LF outside of line
2558   break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate a
2559   line break within text content when a message is transmitted over
2560   HTTP.
2563   Where it is possible, a proxy or gateway from HTTP to a strict MIME
2564   environment &SHOULD; translate all line breaks within the text media
2565   types described in <xref target="canonicalization.and.text.defaults"/> of this document to the RFC 2049
2566   canonical form of CRLF. Note, however, that this might be complicated
2567   by the presence of a Content-Encoding and by the fact that HTTP
2568   allows the use of some character sets which do not use octets 13 and
2569   10 to represent CR and LF, as is the case for some multi-byte
2570   character sets.
2573   Implementors should note that conversion will break any cryptographic
2574   checksums applied to the original content unless the original content
2575   is already in canonical form. Therefore, the canonical form is
2576   recommended for any content that uses such checksums in HTTP.
2581<section title="Conversion of Date Formats" anchor="">
2583   HTTP/1.1 uses a restricted set of date formats (&full-date;) to
2584   simplify the process of date comparison. Proxies and gateways from
2585   other protocols &SHOULD; ensure that any Date header field present in a
2586   message conforms to one of the HTTP/1.1 formats and rewrite the date
2587   if necessary.
[8]2591<section title="Introduction of Content-Encoding" anchor="introduction.of.content-encoding">
2593   RFC 2045 does not include any concept equivalent to HTTP/1.1's
2594   Content-Encoding header field. Since this acts as a modifier on the
2595   media type, proxies and gateways from HTTP to MIME-compliant
2596   protocols &MUST; either change the value of the Content-Type header
2597   field or decode the entity-body before forwarding the message. (Some
2598   experimental applications of Content-Type for Internet mail have used
2599   a media-type parameter of ";conversions=&lt;content-coding&gt;" to perform
2600   a function equivalent to Content-Encoding. However, this parameter is
2601   not part of RFC 2045).
2605<section title="No Content-Transfer-Encoding" anchor="no.content-transfer-encoding">
[85]2607   HTTP does not use the Content-Transfer-Encoding field of RFC
[8]2608   2045. Proxies and gateways from MIME-compliant protocols to HTTP &MUST;
[85]2609   remove any Content-Transfer-Encoding
[8]2610   prior to delivering the response message to an HTTP client.
2613   Proxies and gateways from HTTP to MIME-compliant protocols are
2614   responsible for ensuring that the message is in the correct format
2615   and encoding for safe transport on that protocol, where "safe
2616   transport" is defined by the limitations of the protocol being used.
2617   Such a proxy or gateway &SHOULD; label the data with an appropriate
2618   Content-Transfer-Encoding if doing so will improve the likelihood of
2619   safe transport over the destination protocol.
2623<section title="Introduction of Transfer-Encoding" anchor="introduction.of.transfer-encoding">
[29]2625   HTTP/1.1 introduces the Transfer-Encoding header field (&header-transfer-encoding;).
[8]2626   Proxies/gateways &MUST; remove any transfer-coding prior to
2627   forwarding a message via a MIME-compliant protocol.
2631<section title="MHTML and Line Length Limitations" anchor="mhtml.line.length">
[129]2633   HTTP implementations which share code with MHTML <xref target="RFC2557"/> implementations
[8]2634   need to be aware of MIME line length limitations. Since HTTP does not
2635   have this limitation, HTTP does not fold long lines. MHTML messages
2636   being transported by HTTP follow all conventions of MHTML, including
2637   line length limitations and folding, canonicalization, etc., since
2638   HTTP transports all message-bodies as payload (see <xref target="multipart.types"/>) and
2639   does not interpret the content or any MIME header lines that might be
2640   contained therein.
2645<section title="Additional Features" anchor="additional.features">
[97]2647   <xref target="RFC1945"/> and <xref target="RFC2068"/> document protocol elements used by some
[8]2648   existing HTTP implementations, but not consistently and correctly
2649   across most HTTP/1.1 applications. Implementors are advised to be
2650   aware of these features, but cannot rely upon their presence in, or
2651   interoperability with, other HTTP/1.1 applications. Some of these
2652   describe proposed experimental features, and some describe features
2653   that experimental deployment found lacking that are now addressed in
2654   the base HTTP/1.1 specification.
2657   A number of other headers, such as Content-Disposition and Title,
[97]2658   from SMTP and MIME are also often implemented (see <xref target="RFC2076"/>).
2661<section title="Content-Disposition" anchor="content-disposition">
2662<iref item="Headers" subitem="Content-Disposition" primary="true" x:for-anchor=""/>
2663<iref item="Content-Disposition header" primary="true" x:for-anchor=""/>
[229]2664  <x:anchor-alias value="content-disposition"/>
[357]2665  <x:anchor-alias value="content-disposition-v"/>
[229]2666  <x:anchor-alias value="disposition-type"/>
2667  <x:anchor-alias value="disposition-parm"/>
2668  <x:anchor-alias value="disp-extension-parm"/>
2669  <x:anchor-alias value="disp-extension-token"/>
2670  <x:anchor-alias value="filename-parm"/>
[697]2672   The "Content-Disposition" response-header field has been proposed as a
[8]2673   means for the origin server to suggest a default filename if the user
2674   requests that the content is saved to a file. This usage is derived
[269]2675   from the definition of Content-Disposition in <xref target="RFC2183"/>.
[357]2677<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="content-disposition"/><iref primary="true" item="Grammar" subitem="content-disposition-v"/><iref primary="true" item="Grammar" subitem="disposition-type"/><iref primary="true" item="Grammar" subitem="disposition-parm"/><iref primary="true" item="Grammar" subitem="filename-parm"/><iref primary="true" item="Grammar" subitem="disp-extension-token"/><iref primary="true" item="Grammar" subitem="disp-extension-parm"/>
[366]2678  <x:ref>content-disposition</x:ref> = "Content-Disposition" ":" <x:ref>OWS</x:ref>
[357]2679                        <x:ref>content-disposition-v</x:ref>
[376]2680  <x:ref>content-disposition-v</x:ref> = <x:ref>disposition-type</x:ref>
2681                          *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>disposition-parm</x:ref> )
[334]2682  <x:ref>disposition-type</x:ref> = "attachment" / <x:ref>disp-extension-token</x:ref>
2683  <x:ref>disposition-parm</x:ref> = <x:ref>filename-parm</x:ref> / <x:ref>disp-extension-parm</x:ref>
[229]2684  <x:ref>filename-parm</x:ref> = "filename" "=" <x:ref>quoted-string</x:ref>
2685  <x:ref>disp-extension-token</x:ref> = <x:ref>token</x:ref>
[810]2686  <x:ref>disp-extension-parm</x:ref> = <x:ref>token</x:ref> "=" <x:ref>word</x:ref>
2689   An example is
2691<figure><artwork type="example">
[458]2692  Content-Disposition: attachment; filename="fname.ext"
2695   The receiving user agent &SHOULD-NOT;  respect any directory path
2696   information present in the filename-parm parameter, which is the only
2697   parameter believed to apply to HTTP implementations at this time. The
2698   filename &SHOULD; be treated as a terminal component only.
2701   If this header is used in a response with the application/octet-stream
2702   content-type, the implied suggestion is that the user agent
[746]2703   should not display the response, but directly enter a "save response
2704   as..." dialog.
2707   See <xref target="content-disposition.issues"/> for Content-Disposition security issues.
[99]2712<section title="Compatibility with Previous Versions" anchor="compatibility">
[8]2713<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
[138]2715   Transfer-coding and message lengths all interact in ways that
2716   required fixing exactly when chunked encoding is used (to allow for
2717   transfer encoding that may not be self delimiting); it was important
2718   to straighten out exactly how message lengths are computed.
[29]2721   Charset wildcarding is introduced to avoid explosion of character set
2722   names in accept headers. (<xref target="header.accept-charset"/>)
2725   Content-Base was deleted from the specification: it was not
2726   implemented widely, and there is no simple, safe way to introduce it
2727   without a robust extension mechanism. In addition, it is used in a
[129]2728   similar, but not identical fashion in MHTML <xref target="RFC2557"/>.
2731   A content-coding of "identity" was introduced, to solve problems
2732   discovered in caching. (<xref target="content.codings"/>)
2735   The Alternates<iref item="Alternates header" primary="true"/><iref item="Headers" subitem="Alternate" primary="true"/>, Content-Version<iref item="Content-Version header" primary="true"/><iref item="Headers" subitem="Content-Version" primary="true"/>, Derived-From<iref item="Derived-From header" primary="true"/><iref item="Headers" subitem="Derived-From" primary="true"/>, Link<iref item="Link header" primary="true"/><iref item="Headers" subitem="Link" primary="true"/>, URI<iref item="URI header" primary="true"/><iref item="Headers" subitem="URI" primary="true"/>, Public<iref item="Public header" primary="true"/><iref item="Headers" subitem="Public" primary="true"/> and
2736   Content-Base<iref item="Content-Base header" primary="true"/><iref item="Headers" subitem="Content-Base" primary="true"/> header fields were defined in previous versions of this
[268]2737   specification, but not commonly implemented. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.2"/>.
2741<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2743  Clarify contexts that charset is used in.
2744  (<xref target="character.sets"/>)
[712]2747  Remove base URI setting semantics for Content-Location due to poor
[714]2748  implementation support, which was caused by too many broken servers emitting
2749  bogus Content-Location headers, and also the potentially undesirable effect
2750  of potentially breaking relative links in content-negotiated resources.
[712]2751  (<xref target="header.content-location"/>)
[104]2754  Remove reference to non-existant identity transfer-coding value tokens.
2755  (<xref target="no.content-transfer-encoding"/>)
[680]2761<?BEGININC p3-payload.abnf-appendix ?>
[427]2762<section xmlns:x="" title="Collected ABNF" anchor="collected.abnf">
2764<artwork type="abnf" name="p3-payload.parsed-abnf">
2765<x:ref>Accept</x:ref> = "Accept:" OWS Accept-v
2766<x:ref>Accept-Charset</x:ref> = "Accept-Charset:" OWS Accept-Charset-v
2767<x:ref>Accept-Charset-v</x:ref> = *( "," OWS ) ( charset / "*" ) [ OWS ";" OWS "q="
[425]2768 qvalue ] *( OWS "," [ OWS ( charset / "*" ) [ OWS ";" OWS "q="
2769 qvalue ] ] )
[427]2770<x:ref>Accept-Encoding</x:ref> = "Accept-Encoding:" OWS Accept-Encoding-v
2771<x:ref>Accept-Encoding-v</x:ref> = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] )
[425]2772 ) *( OWS "," [ OWS codings [ OWS ";" OWS "q=" qvalue ] ] ) ]
[427]2773<x:ref>Accept-Language</x:ref> = "Accept-Language:" OWS Accept-Language-v
2774<x:ref>Accept-Language-v</x:ref> = *( "," OWS ) language-range [ OWS ";" OWS "q="
[425]2775 qvalue ] *( OWS "," [ OWS language-range [ OWS ";" OWS "q=" qvalue ]
2776 ] )
[427]2777<x:ref>Accept-v</x:ref> = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
[425]2778 OWS media-range [ accept-params ] ] ) ]
[427]2780<x:ref>Content-Encoding</x:ref> = "Content-Encoding:" OWS Content-Encoding-v
2781<x:ref>Content-Encoding-v</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
[425]2782 content-coding ] )
[427]2783<x:ref>Content-Language</x:ref> = "Content-Language:" OWS Content-Language-v
2784<x:ref>Content-Language-v</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
[425]2785 language-tag ] )
[678]2786<x:ref>Content-Length</x:ref> = &lt;Content-Length, defined in [Part1], Section 9.2&gt;
[427]2787<x:ref>Content-Location</x:ref> = "Content-Location:" OWS Content-Location-v
2788<x:ref>Content-Location-v</x:ref> = absolute-URI / partial-URI
2789<x:ref>Content-MD5</x:ref> = "Content-MD5:" OWS Content-MD5-v
2790<x:ref>Content-MD5-v</x:ref> = &lt;base64 of 128 bit MD5 digest as per [RFC1864]&gt;
2791<x:ref>Content-Range</x:ref> = &lt;Content-Range, defined in [Part5], Section 5.2&gt;
2792<x:ref>Content-Type</x:ref> = "Content-Type:" OWS Content-Type-v
2793<x:ref>Content-Type-v</x:ref> = media-type
[538]2795<x:ref>Expires</x:ref> = &lt;Expires, defined in [Part6], Section 3.3&gt;
2797<x:ref>Last-Modified</x:ref> = &lt;Last-Modified, defined in [Part4], Section 6.6&gt;
2799<x:ref>MIME-Version</x:ref> = "MIME-Version:" OWS MIME-Version-v
2800<x:ref>MIME-Version-v</x:ref> = 1*DIGIT "." 1*DIGIT
2802<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
[648]2804<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
[810]2805<x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" word ]
[427]2806<x:ref>accept-params</x:ref> = OWS ";" OWS "q=" qvalue *accept-ext
2807<x:ref>attribute</x:ref> = token
2809<x:ref>charset</x:ref> = token
2810<x:ref>codings</x:ref> = ( content-coding / "*" )
2811<x:ref>content-coding</x:ref> = token
2812<x:ref>content-disposition</x:ref> = "Content-Disposition:" OWS
[425]2813 content-disposition-v
[427]2814<x:ref>content-disposition-v</x:ref> = disposition-type *( OWS ";" OWS
[425]2815 disposition-parm )
[810]2817<x:ref>disp-extension-parm</x:ref> = token "=" word
[427]2818<x:ref>disp-extension-token</x:ref> = token
2819<x:ref>disposition-parm</x:ref> = filename-parm / disp-extension-parm
2820<x:ref>disposition-type</x:ref> = "attachment" / disp-extension-token
2822<x:ref>entity-body</x:ref> = *OCTET
2823<x:ref>entity-header</x:ref> = Content-Encoding / Content-Language / Content-Length
[425]2824 / Content-Location / Content-MD5 / Content-Range / Content-Type /
2825 Expires / Last-Modified / extension-header
[647]2826<x:ref>extension-header</x:ref> = header-field
2828<x:ref>filename-parm</x:ref> = "filename=" quoted-string
[678]2830<x:ref>header-field</x:ref> = &lt;header-field, defined in [Part1], Section 3.2&gt;
[427]2832<x:ref>language-range</x:ref> = &lt;language-range, defined in [RFC4647], Section 2.1&gt;
[690]2833<x:ref>language-tag</x:ref> = &lt;Language-Tag, defined in [RFC5646], Section 2.1&gt;
2835<x:ref>media-range</x:ref> = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
[425]2836 ";" OWS parameter )
[427]2837<x:ref>media-type</x:ref> = type "/" subtype *( OWS ";" OWS parameter )
2839<x:ref>parameter</x:ref> = attribute "=" value
[648]2840<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
2842<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
[678]2843<x:ref>qvalue</x:ref> = &lt;qvalue, defined in [Part1], Section 6.4&gt;
2845<x:ref>subtype</x:ref> = token
2847<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
2848<x:ref>type</x:ref> = token
[810]2850<x:ref>value</x:ref> = word
2852<x:ref>word</x:ref> = &lt;word, defined in [Part1], Section 1.2.2&gt;
[532]2855<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
2856; Accept defined but not used
[425]2857; Accept-Charset defined but not used
2858; Accept-Encoding defined but not used
2859; Accept-Language defined but not used
2860; MIME-Version defined but not used
2861; content-disposition defined but not used
2862; entity-body defined but not used
2863; entity-header defined but not used
[680]2865<?ENDINC p3-payload.abnf-appendix ?>
[252]2867<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
2869<section title="Since RFC2616">
2871  Extracted relevant partitions from <xref target="RFC2616"/>.
2875<section title="Since draft-ietf-httpbis-p3-payload-00">
[116]2877  Closed issues:
2878  <list style="symbols">
2879    <t>
[324]2880      <eref target=""/>:
[116]2881      "Media Type Registrations"
2882      (<eref target=""/>)
2883    </t>
2884    <t>
[324]2885      <eref target=""/>:
[116]2886      "Clarification regarding quoting of charset values"
2887      (<eref target=""/>)
2888    </t>
2889    <t>
[324]2890      <eref target=""/>:
[116]2891      "Remove 'identity' token references"
2892      (<eref target=""/>)
2893    </t>
2894    <t>
[324]2895      <eref target=""/>:
[126]2896      "Accept-Encoding BNF"
2897    </t>
2898    <t>
[324]2899      <eref target=""/>:
[152]2900      "Normative and Informative references"
2901    </t>
2902    <t>
[324]2903      <eref target=""/>:
[116]2904      "RFC1700 references"
2905    </t>
[122]2906    <t>
[324]2907      <eref target=""/>:
[200]2908      "Updating to RFC4288"
2909    </t>
2910    <t>
[324]2911      <eref target=""/>:
[129]2912      "Informative references"
2913    </t>
2914    <t>
[324]2915      <eref target=""/>:
[123]2916      "ISO-8859-1 Reference"
2917    </t>
2918    <t>
[324]2919      <eref target=""/>:
[122]2920      "Encoding References Normative"
2921    </t>
[131]2922    <t>
[324]2923      <eref target=""/>:
[131]2924      "Normative up-to-date references"
2925    </t>
[116]2926  </list>
[170]2930<section title="Since draft-ietf-httpbis-p3-payload-01">
[324]2932  Ongoing work on ABNF conversion (<eref target=""/>):
[205]2933  <list style="symbols">
2934    <t>
2935      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2936    </t>
2937  </list>
[252]2941<section title="Since draft-ietf-httpbis-p3-payload-02" anchor="changes.since.02">
[232]2943  Closed issues:
2944  <list style="symbols">
2945    <t>
[324]2946      <eref target=""/>:
[251]2947      "Quoting Charsets"
2948    </t>
2949    <t>
[324]2950      <eref target=""/>:
[232]2951      "Classification for Allow header"
2952    </t>
[248]2953    <t>
[324]2954      <eref target=""/>:
[248]2955      "missing default for qvalue in description of Accept-Encoding"
2956    </t>
[232]2957  </list>
[324]2960  Ongoing work on IANA Message Header Registration (<eref target=""/>):
[253]2961  <list style="symbols">
2962    <t>
2963      Reference RFC 3984, and update header registrations for headers defined
2964      in this document.
2965    </t>
2966  </list>
[267]2970<section title="Since draft-ietf-httpbis-p3-payload-03" anchor="changes.since.03">
[269]2972  Closed issues:
2973  <list style="symbols">
2974    <t>
[297]2975      <eref target=""/>:
2976      "Quoting Charsets"
2977    </t>
2978    <t>
[303]2979      <eref target=""/>:
2980      "language tag matching (Accept-Language) vs RFC4647"
2981    </t>
2982    <t>
[277]2983      <eref target=""/>:
[269]2984      "RFC 1806 has been replaced by RFC2183"
2985    </t>
2986  </list>
2989  Other changes:
2990  <list style="symbols">
2991    <t>
2992      <eref target=""/>:
2993      "Encoding References Normative" -- rephrase the annotation and reference
2994      <xref target="BCP97"/>.
2995    </t>
2996  </list>
[269]2998 </section>
[323]3000<section title="Since draft-ietf-httpbis-p3-payload-04" anchor="changes.since.04">
[327]3002  Closed issues:
3003  <list style="symbols">
3004    <t>
3005      <eref target=""/>:
3006      "RFC 2822 is updated by RFC 5322"
3007    </t>
3008  </list>
3011  Ongoing work on ABNF conversion (<eref target=""/>):
3012  <list style="symbols">
3013    <t>
3014      Use "/" instead of "|" for alternatives.
3015    </t>
[357]3016    <t>
3017      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3018      whitespace ("OWS") and required whitespace ("RWS").
3019    </t>
3020    <t>
3021      Rewrite ABNFs to spell out whitespace rules, factor out
3022      header value format definitions.
3023    </t>
[334]3024  </list>
[382]3028<section title="Since draft-ietf-httpbis-p3-payload-05" anchor="changes.since.05">
[385]3030  Closed issues:
3031  <list style="symbols">
3032    <t>
3033      <eref target=""/>:
3034      "Join "Differences Between HTTP Entities and RFC 2045 Entities"?"
3035    </t>
3036  </list>
[543]3039  Final work on ABNF conversion (<eref target=""/>):
[421]3040  <list style="symbols">
3041    <t>
[424]3042      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
[421]3043    </t>
3044  </list>
3047  Other changes:
3048  <list style="symbols">
3049    <t>
3050      Move definition of quality values into Part 1.
3051    </t>
3052  </list>
[547]3056<section title="Since draft-ietf-httpbis-p3-payload-06" anchor="changes.since.06">
[577]3058  Closed issues:
3059  <list style="symbols">
3060    <t>
3061      <eref target=""/>:
3062      "Content-Location isn't special"
3063    </t>
[592]3064    <t>
3065      <eref target=""/>:
3066      "Content Sniffing"
3067    </t>
[577]3068  </list>
[604]3072<section title="Since draft-ietf-httpbis-p3-payload-07" anchor="changes.since.07">
[613]3074  Closed issues:
3075  <list style="symbols">
3076    <t>
[670]3077      <eref target=""/>:
[613]3078      "Updated reference for language tags"
3079    </t>
[663]3080    <t>
[716]3081      <eref target=""/>:
3082      "Clarify rules for determining what entities a response carries"
3083    </t>
3084    <t>
[712]3085      <eref target=""/>:
3086      "Content-Location base-setting problems"
3087    </t>
3088    <t>
[663]3089      <eref target=""/>:
3090      "Content Sniffing"
3091    </t>
[670]3092    <t>
3093      <eref target=""/>:
3094      "pick IANA policy (RFC5226) for Transfer Coding / Content Coding"
3095    </t>
[673]3096    <t>
3097      <eref target=""/>:
3098      "move definitions of gzip/deflate/compress to part 1"
3099    </t>
[613]3100  </list>
3103  Partly resolved issues:
3104  <list style="symbols">
3105    <t>
3106      <eref target=""/>:
3107      "update IANA requirements wrt Transfer-Coding values" (add the
3108      IANA Considerations subsection)
3109    </t>
[668]3110    <t>
3111      <eref target=""/>:
3112      "update IANA requirements wrt Content-Coding values" (add the
3113      IANA Considerations subsection)
3114    </t>
[667]3115  </list>
[720]3119<section title="Since draft-ietf-httpbis-p3-payload-08" anchor="changes.since.08">
[724]3121  Closed issues:
3122  <list style="symbols">
3123    <t>
[745]3124      <eref target=""/>:
3125      "Content Negotiation for media types"
3126    </t>
3127    <t>
[724]3128      <eref target=""/>:
3129      "Accept-Language: which RFC4647 filtering?"
3130    </t>
3131  </list>
[773]3135<section title="Since draft-ietf-httpbis-p3-payload-09" anchor="changes.since.09">
[808]3137  Closed issues:
3138  <list style="symbols">
3139    <t>
3140      <eref target=""/>:
3141      "IANA registry for content/transfer encodings"
3142    </t>
[810]3143    <t>
[831]3144      <eref target=""/>:
3145      "Content Sniffing"
3146    </t>
3147    <t>
[810]3148      <eref target=""/>:
3149      "use of term "word" when talking about header structure"
3150    </t>
[808]3151  </list>
3154  Partly resolved issues:
3155  <list style="symbols">
3156    <t>
3157      <eref target=""/>:
3158      "Term for the requested resource's URI"
3159    </t>
3160  </list>
[841]3164<section title="Since draft-ietf-httpbis-p3-payload-10" anchor="changes.since.10">
3166  None yet.
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