source: draft-ietf-httpbis/latest/p2-semantics.xml @ 357

Last change on this file since 357 was 357, checked in by julian.reschke@…, 14 years ago

Rewrite header ABNFs to spell out whitespace rules, factor out value format definitions. (related to #36)

  • Property svn:eol-style set to native
File size: 144.3 KB
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
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>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "November">
16  <!ENTITY ID-YEAR "2008">
17  <!ENTITY messaging                  "<xref target='Part1' xmlns:x=''/>">
18  <!ENTITY payload                    "<xref target='Part3' xmlns:x=''/>">
19  <!ENTITY conditional                "<xref target='Part4' xmlns:x=''/>">
20  <!ENTITY range                      "<xref target='Part5' xmlns:x=''/>">
21  <!ENTITY caching                    "<xref target='Part6' xmlns:x=''/>">
22  <!ENTITY auth                       "<xref target='Part7' xmlns:x=''/>">
23  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x=''/>">
24  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
25  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
26  <!ENTITY general-syntax             "<xref target='Part1' x:rel='#general.syntax' xmlns:x=''/>">
27  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
28  <!ENTITY full-date                  "<xref target='Part1' x:rel='' xmlns:x=''/>">
29  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
30  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
31  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
32  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
33  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
34  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
35  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
36  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
37  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
38  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
39  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
40  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
41  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
42  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
43  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
44  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
45  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
46  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
47  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
48  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
49  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
50  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
51  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
52  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
53  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
54  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
55  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
56  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
57  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
58  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
59  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
60  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
61  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
62  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
63  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='' xmlns:x=''/>">
65<?rfc toc="yes" ?>
66<?rfc symrefs="yes" ?>
67<?rfc sortrefs="yes" ?>
68<?rfc compact="yes"?>
69<?rfc subcompact="no" ?>
70<?rfc linkmailto="no" ?>
71<?rfc editing="no" ?>
72<?rfc comments="yes"?>
73<?rfc inline="yes"?>
74<?rfc-ext allow-markup-in-artwork="yes" ?>
75<?rfc-ext include-references-in-index="yes" ?>
76<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
77     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
78     xmlns:x=''
79     xmlns:rdf=''>
82  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
84  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
85    <organization abbrev="Day Software">Day Software</organization>
86    <address>
87      <postal>
88        <street>23 Corporate Plaza DR, Suite 280</street>
89        <city>Newport Beach</city>
90        <region>CA</region>
91        <code>92660</code>
92        <country>USA</country>
93      </postal>
94      <phone>+1-949-706-5300</phone>
95      <facsimile>+1-949-706-5305</facsimile>
96      <email></email>
97      <uri></uri>
98    </address>
99  </author>
101  <author initials="J." surname="Gettys" fullname="Jim Gettys">
102    <organization>One Laptop per Child</organization>
103    <address>
104      <postal>
105        <street>21 Oak Knoll Road</street>
106        <city>Carlisle</city>
107        <region>MA</region>
108        <code>01741</code>
109        <country>USA</country>
110      </postal>
111      <email></email>
112      <uri></uri>
113    </address>
114  </author>
116  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
117    <organization abbrev="HP">Hewlett-Packard Company</organization>
118    <address>
119      <postal>
120        <street>HP Labs, Large Scale Systems Group</street>
121        <street>1501 Page Mill Road, MS 1177</street>
122        <city>Palo Alto</city>
123        <region>CA</region>
124        <code>94304</code>
125        <country>USA</country>
126      </postal>
127      <email></email>
128    </address>
129  </author>
131  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
132    <organization abbrev="Microsoft">Microsoft Corporation</organization>
133    <address>
134      <postal>
135        <street>1 Microsoft Way</street>
136        <city>Redmond</city>
137        <region>WA</region>
138        <code>98052</code>
139        <country>USA</country>
140      </postal>
141      <email></email>
142    </address>
143  </author>
145  <author initials="L." surname="Masinter" fullname="Larry Masinter">
146    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
147    <address>
148      <postal>
149        <street>345 Park Ave</street>
150        <city>San Jose</city>
151        <region>CA</region>
152        <code>95110</code>
153        <country>USA</country>
154      </postal>
155      <email></email>
156      <uri></uri>
157    </address>
158  </author>
160  <author initials="P." surname="Leach" fullname="Paul J. Leach">
161    <organization abbrev="Microsoft">Microsoft Corporation</organization>
162    <address>
163      <postal>
164        <street>1 Microsoft Way</street>
165        <city>Redmond</city>
166        <region>WA</region>
167        <code>98052</code>
168      </postal>
169      <email></email>
170    </address>
171  </author>
173  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
174    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
175    <address>
176      <postal>
177        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
178        <street>The Stata Center, Building 32</street>
179        <street>32 Vassar Street</street>
180        <city>Cambridge</city>
181        <region>MA</region>
182        <code>02139</code>
183        <country>USA</country>
184      </postal>
185      <email></email>
186      <uri></uri>
187    </address>
188  </author>
190  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
191    <organization abbrev="W3C">World Wide Web Consortium</organization>
192    <address>
193      <postal>
194        <street>W3C / ERCIM</street>
195        <street>2004, rte des Lucioles</street>
196        <city>Sophia-Antipolis</city>
197        <region>AM</region>
198        <code>06902</code>
199        <country>France</country>
200      </postal>
201      <email></email>
202      <uri></uri>
203    </address>
204  </author>
206  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
207    <organization abbrev="greenbytes">greenbytes GmbH</organization>
208    <address>
209      <postal>
210        <street>Hafenweg 16</street>
211        <city>Muenster</city><region>NW</region><code>48155</code>
212        <country>Germany</country>
213      </postal>
214      <phone>+49 251 2807760</phone>   
215      <facsimile>+49 251 2807761</facsimile>   
216      <email></email>       
217      <uri></uri>     
218    </address>
219  </author>
221  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
225   The Hypertext Transfer Protocol (HTTP) is an application-level
226   protocol for distributed, collaborative, hypermedia information
227   systems. HTTP has been in use by the World Wide Web global information
228   initiative since 1990. This document is Part 2 of the seven-part specification
229   that defines the protocol referred to as "HTTP/1.1" and, taken together,
230   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
231   as expressed by request methods, request-header fields, response status codes,
232   and response-header fields.
236<note title="Editorial Note (To be removed by RFC Editor)">
237  <t>
238    Discussion of this draft should take place on the HTTPBIS working group
239    mailing list ( The current issues list is
240    at <eref target=""/>
241    and related documents (including fancy diffs) can be found at
242    <eref target=""/>.
243  </t>
244  <t>
245    The changes in this draft are summarized in <xref target="changes.since.04"/>.
246  </t>
250<section title="Introduction" anchor="introduction">
252   This document defines HTTP/1.1 request and response semantics.  Each HTTP
253   message, as defined in &messaging;, is in the form of either a request or
254   a response.  An HTTP server listens on a connection for HTTP requests and
255   responds to each request, in the order received on that connection, with
256   one or more HTTP response messages.  This document defines the commonly
257   agreed upon semantics of the HTTP uniform interface, the intentions defined
258   by each request method, and the various response messages that might be
259   expected as a result of applying that method for the requested resource.
262   This document is currently disorganized in order to minimize the changes
263   between drafts and enable reviewers to see the smaller errata changes.
264   The next draft will reorganize the sections to better reflect the content.
265   In particular, the sections will be ordered according to the typical
266   processing of an HTTP request message (after message parsing): resource
267   mapping, general header fields, methods, request modifiers, response
268   status, and resource metadata.  The current mess reflects how widely
269   dispersed these topics and associated requirements had become in
270   <xref target="RFC2616"/>.
273<section title="Requirements" anchor="intro.requirements">
275   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
276   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
277   document are to be interpreted as described in <xref target="RFC2119"/>.
280   An implementation is not compliant if it fails to satisfy one or more
281   of the &MUST; or &REQUIRED; level requirements for the protocols it
282   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
283   level and all the &SHOULD; level requirements for its protocols is said
284   to be "unconditionally compliant"; one that satisfies all the &MUST;
285   level requirements but not all the &SHOULD; level requirements for its
286   protocols is said to be "conditionally compliant."
291<section title="Notational Conventions and Generic Grammar" anchor="notation">
292  <x:anchor-alias value="comment"/>
293  <x:anchor-alias value="DIGIT"/>
294  <x:anchor-alias value="quoted-string"/>
295  <x:anchor-alias value="token"/>
296  <x:anchor-alias value="BWS"/>
297  <x:anchor-alias value="OWS"/>
298  <x:anchor-alias value="RWS"/>
300  This specification uses the ABNF syntax defined in &notation-abnf; and
301  the core rules defined in &basic-rules;:
302  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
303  <eref target=""/>.</cref>
305<figure><artwork type="abnf2616">
306  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
308<figure><artwork type="abnf2616">
309  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
310  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
311  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
312  <x:ref>BWS</x:ref>           = &lt;BWS, defined in &basic-rules;&gt;
313  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
314  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
316<t anchor="abnf.dependencies">
317  <x:anchor-alias value="absoluteURI"/>
318  <x:anchor-alias value="Accept"/>
319  <x:anchor-alias value="Accept-Charset"/>
320  <x:anchor-alias value="Accept-Encoding"/>
321  <x:anchor-alias value="Accept-Language"/>
322  <x:anchor-alias value="Accept-Ranges"/>
323  <x:anchor-alias value="Age"/>
324  <x:anchor-alias value="Authorization"/>
325  <x:anchor-alias value="ETag"/>
326  <x:anchor-alias value="fragment"/>
327  <x:anchor-alias value="Host"/>
328  <x:anchor-alias value="HTTP-date"/>
329  <x:anchor-alias value="If-Match"/>
330  <x:anchor-alias value="If-Modified-Since"/>
331  <x:anchor-alias value="If-None-Match"/>
332  <x:anchor-alias value="If-Range"/>
333  <x:anchor-alias value="If-Unmodified-Since"/>
334  <x:anchor-alias value="product"/>
335  <x:anchor-alias value="Proxy-Authenticate"/>
336  <x:anchor-alias value="Proxy-Authorization"/>
337  <x:anchor-alias value="Range"/>
338  <x:anchor-alias value="relativeURI"/>
339  <x:anchor-alias value="TE"/>
340  <x:anchor-alias value="Vary"/>
341  <x:anchor-alias value="WWW-Authenticate"/>
342  The ABNF rules below are defined in other parts:
344<figure><!--Part1--><artwork type="abnf2616">
345  <x:ref>absoluteURI</x:ref>   = &lt;absoluteURI, defined in &general-syntax;&gt;
346  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &general-syntax;&gt;
347  <x:ref>Host</x:ref>          = &lt;Host, defined in &header-host;&gt;
348  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
349  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
350  <x:ref>relativeURI</x:ref>   = &lt;relativeURI, defined in &general-syntax;&gt;
351  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
353<figure><!--Part3--><artwork type="abnf2616">
354  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
355  <x:ref>Accept-Charset</x:ref> =
356             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
357  <x:ref>Accept-Encoding</x:ref> =
358             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
359  <x:ref>Accept-Language</x:ref> =
360             &lt;Accept-Language, defined in &header-accept-language;&gt;
362<figure><!--Part4--><artwork type="abnf2616">
363  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
364  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
365  <x:ref>If-Modified-Since</x:ref> =
366             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
367  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
368  <x:ref>If-Unmodified-Since</x:ref> =
369             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
371<figure><!--Part5--><artwork type="abnf2616">
372  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
373  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
374  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
376<figure><!--Part6--><artwork type="abnf2616">
377  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
378  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
380<figure><artwork type="abnf2616">
381  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
382  <x:ref>Proxy-Authenticate</x:ref> =
383             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
384  <x:ref>Proxy-Authorization</x:ref> =
385             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
386  <x:ref>WWW-Authenticate</x:ref> =
387             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
391<section title="Method" anchor="method">
392  <x:anchor-alias value="Method"/>
393  <x:anchor-alias value="extension-method"/>
395   The Method  token indicates the method to be performed on the
396   resource identified by the Request-URI. The method is case-sensitive.
398<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
399  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
400                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
401                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
402                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
403                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
404                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
405                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
406                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
407                 / <x:ref>extension-method</x:ref>
408  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
411   The list of methods allowed by a resource can be specified in an
412   Allow header field (<xref target="header.allow"/>). The return code of the response
413   always notifies the client whether a method is currently allowed on a
414   resource, since the set of allowed methods can change dynamically. An
415   origin server &SHOULD; return the status code 405 (Method Not Allowed)
416   if the method is known by the origin server but not allowed for the
417   requested resource, and 501 (Not Implemented) if the method is
418   unrecognized or not implemented by the origin server. The methods GET
419   and HEAD &MUST; be supported by all general-purpose servers. All other
420   methods are &OPTIONAL;; however, if the above methods are implemented,
421   they &MUST; be implemented with the same semantics as those specified
422   in <xref target="method.definitions"/>.
425<section title="Method Registry" anchor="method.registry">
427  The HTTP Method Registry defines the name space for the Method token in the
428  Request line of an HTTP request.
431  Registrations &MUST; include the following fields:
432  <list style="symbols">
433    <t>Method Name (see <xref target="method"/>)</t>
434    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
435    <t>Pointer to specification text</t>
436  </list>
439  Values to be added to this name space are subject to IETF review
440  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
441  new method names should be traceable through statuses of either 'Obsoletes'
442  or 'Updates' to this document.
445  The registry itself is maintained at <eref target=""/>.
450<section title="Request Header Fields" anchor="request.header.fields">
451  <x:anchor-alias value="extension-code"/>
452  <x:anchor-alias value="request-header"/>
454   The request-header fields allow the client to pass additional
455   information about the request, and about the client itself, to the
456   server. These fields act as request modifiers, with semantics
457   equivalent to the parameters on a programming language method
458   invocation.
460<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
461  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
462                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
463                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
464                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
465                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
466                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
467                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
468                 / <x:ref>Host</x:ref>                     ; &header-host;
469                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
470                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
471                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
472                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
473                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
474                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
475                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
476                 / <x:ref>Range</x:ref>                    ; &header-range;
477                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
478                 / <x:ref>TE</x:ref>                       ; &header-te;
479                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
482   Request-header field names can be extended reliably only in
483   combination with a change in the protocol version. However, new or
484   experimental header fields &MAY; be given the semantics of request-header
485   fields if all parties in the communication recognize them to
486   be request-header fields. Unrecognized header fields are treated as
487   entity-header fields.
491<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
492  <x:anchor-alias value="Reason-Phrase"/>
493  <x:anchor-alias value="Status-Code"/>
495   The Status-Code element is a 3-digit integer result code of the
496   attempt to understand and satisfy the request. The status codes listed
497   below are defined in <xref target=""/>.
498   The Reason-Phrase is intended to give a short
499   textual description of the Status-Code. The Status-Code is intended
500   for use by automata and the Reason-Phrase is intended for the human
501   user. The client is not required to examine or display the Reason-Phrase.
504   The individual values of the numeric status codes defined for
505   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
506   presented below. The reason phrases listed here are only
507   recommendations -- they &MAY; be replaced by local equivalents without
508   affecting the protocol.
510<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="extension-code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/>
511  <x:ref>Status-Code</x:ref>    =
512         "100"  ; <xref target="status.100"/>: Continue
513       / "101"  ; <xref target="status.101"/>: Switching Protocols
514       / "200"  ; <xref target="status.200"/>: OK
515       / "201"  ; <xref target="status.201"/>: Created
516       / "202"  ; <xref target="status.202"/>: Accepted
517       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
518       / "204"  ; <xref target="status.204"/>: No Content
519       / "205"  ; <xref target="status.205"/>: Reset Content
520       / "206"  ; <xref target="status.206"/>: Partial Content
521       / "300"  ; <xref target="status.300"/>: Multiple Choices
522       / "301"  ; <xref target="status.301"/>: Moved Permanently
523       / "302"  ; <xref target="status.302"/>: Found
524       / "303"  ; <xref target="status.303"/>: See Other
525       / "304"  ; <xref target="status.304"/>: Not Modified
526       / "305"  ; <xref target="status.305"/>: Use Proxy
527       / "307"  ; <xref target="status.307"/>: Temporary Redirect
528       / "400"  ; <xref target="status.400"/>: Bad Request
529       / "401"  ; <xref target="status.401"/>: Unauthorized
530       / "402"  ; <xref target="status.402"/>: Payment Required
531       / "403"  ; <xref target="status.403"/>: Forbidden
532       / "404"  ; <xref target="status.404"/>: Not Found
533       / "405"  ; <xref target="status.405"/>: Method Not Allowed
534       / "406"  ; <xref target="status.406"/>: Not Acceptable
535       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
536       / "408"  ; <xref target="status.408"/>: Request Time-out
537       / "409"  ; <xref target="status.409"/>: Conflict
538       / "410"  ; <xref target="status.410"/>: Gone
539       / "411"  ; <xref target="status.411"/>: Length Required
540       / "412"  ; <xref target="status.412"/>: Precondition Failed
541       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
542       / "414"  ; <xref target="status.414"/>: Request-URI Too Large
543       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
544       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
545       / "417"  ; <xref target="status.417"/>: Expectation Failed
546       / "500"  ; <xref target="status.500"/>: Internal Server Error
547       / "501"  ; <xref target="status.501"/>: Not Implemented
548       / "502"  ; <xref target="status.502"/>: Bad Gateway
549       / "503"  ; <xref target="status.503"/>: Service Unavailable
550       / "504"  ; <xref target="status.504"/>: Gateway Time-out
551       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
552       / <x:ref>extension-code</x:ref>
554  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
555  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
558   HTTP status codes are extensible. HTTP applications are not required
559   to understand the meaning of all registered status codes, though such
560   understanding is obviously desirable. However, applications &MUST;
561   understand the class of any status code, as indicated by the first
562   digit, and treat any unrecognized response as being equivalent to the
563   x00 status code of that class, with the exception that an
564   unrecognized response &MUST-NOT; be cached. For example, if an
565   unrecognized status code of 431 is received by the client, it can
566   safely assume that there was something wrong with its request and
567   treat the response as if it had received a 400 status code. In such
568   cases, user agents &SHOULD; present to the user the entity returned
569   with the response, since that entity is likely to include human-readable
570   information which will explain the unusual status.
573<section title="Status Code Registry" anchor="status.code.registry">
575  The HTTP Status Code Registry defines the name space for the Status-Code
576  token in the Status line of an HTTP response.
579  Values to be added to this name space are subject to IETF review
580  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
581  new status codes should be traceable through statuses of either 'Obsoletes'
582  or 'Updates' to this document.
585  The registry itself is maintained at <eref target=""/>.
591<section title="Response Header Fields" anchor="response.header.fields">
592  <x:anchor-alias value="response-header"/>
594   The response-header fields allow the server to pass additional
595   information about the response which cannot be placed in the Status-Line.
596   These header fields give information about the server and about
597   further access to the resource identified by the Request-URI.
599<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
600  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
601                  / <x:ref>Age</x:ref>                     ; &header-age;
602                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
603                  / <x:ref>ETag</x:ref>                    ; &header-etag;
604                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
605                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
606                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
607                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
608                  / <x:ref>Vary</x:ref>                    ; &header-vary;
609                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
612   Response-header field names can be extended reliably only in
613   combination with a change in the protocol version. However, new or
614   experimental header fields &MAY; be given the semantics of response-header
615   fields if all parties in the communication recognize them to
616   be response-header fields. Unrecognized header fields are treated as
617   entity-header fields.
621<section title="Entity" anchor="entity">
623   Request and Response messages &MAY; transfer an entity if not otherwise
624   restricted by the request method or response status code. An entity
625   consists of entity-header fields and an entity-body, although some
626   responses will only include the entity-headers. HTTP entity-body and
627   entity-header fields are defined in &payload;.
630   An entity-body is only present in a message when a message-body is
631   present, as described in &message-body;. The entity-body is obtained
632   from the message-body by decoding any Transfer-Encoding that might
633   have been applied to ensure safe and proper transfer of the message.
638<section title="Method Definitions" anchor="method.definitions">
640   The set of common methods for HTTP/1.1 is defined below. Although
641   this set can be expanded, additional methods cannot be assumed to
642   share the same semantics for separately extended clients and servers.
645<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
647<section title="Safe Methods" anchor="safe.methods">
648<iref item="Safe Methods" primary="true"/>
650   Implementors should be aware that the software represents the user in
651   their interactions over the Internet, and should be careful to allow
652   the user to be aware of any actions they might take which may have an
653   unexpected significance to themselves or others.
656   In particular, the convention has been established that the GET and
657   HEAD methods &SHOULD-NOT;  have the significance of taking an action
658   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
659   This allows user agents to represent other methods, such as POST, PUT
660   and DELETE, in a special way, so that the user is made aware of the
661   fact that a possibly unsafe action is being requested.
664   Naturally, it is not possible to ensure that the server does not
665   generate side-effects as a result of performing a GET request; in
666   fact, some dynamic resources consider that a feature. The important
667   distinction here is that the user did not request the side-effects,
668   so therefore cannot be held accountable for them.
672<section title="Idempotent Methods" anchor="idempotent.methods">
673<iref item="Idempotent Methods" primary="true"/>
675   Methods can also have the property of "idempotence" in that (aside
676   from error or expiration issues) the side-effects of N &gt; 0 identical
677   requests is the same as for a single request. The methods GET, HEAD,
678   PUT and DELETE share this property. Also, the methods OPTIONS and
679   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
682   However, it is possible that a sequence of several requests is non-idempotent,
683   even if all of the methods executed in that sequence are
684   idempotent. (A sequence is idempotent if a single execution of the
685   entire sequence always yields a result that is not changed by a
686   reexecution of all, or part, of that sequence.) For example, a
687   sequence is non-idempotent if its result depends on a value that is
688   later modified in the same sequence.
691   A sequence that never has side effects is idempotent, by definition
692   (provided that no concurrent operations are being executed on the
693   same set of resources).
698<section title="OPTIONS" anchor="OPTIONS">
699  <rdf:Description>
700    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
701  </rdf:Description>
702  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
703  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
705   The OPTIONS method represents a request for information about the
706   communication options available on the request/response chain
707   identified by the Request-URI. This method allows the client to
708   determine the options and/or requirements associated with a resource,
709   or the capabilities of a server, without implying a resource action
710   or initiating a resource retrieval.
713   Responses to this method are not cacheable.
716   If the OPTIONS request includes an entity-body (as indicated by the
717   presence of Content-Length or Transfer-Encoding), then the media type
718   &MUST; be indicated by a Content-Type field. Although this
719   specification does not define any use for such a body, future
720   extensions to HTTP might use the OPTIONS body to make more detailed
721   queries on the server.
724   If the Request-URI is an asterisk ("*"), the OPTIONS request is
725   intended to apply to the server in general rather than to a specific
726   resource. Since a server's communication options typically depend on
727   the resource, the "*" request is only useful as a "ping" or "no-op"
728   type of method; it does nothing beyond allowing the client to test
729   the capabilities of the server. For example, this can be used to test
730   a proxy for HTTP/1.1 compliance (or lack thereof).
733   If the Request-URI is not an asterisk, the OPTIONS request applies
734   only to the options that are available when communicating with that
735   resource.
738   A 200 response &SHOULD; include any header fields that indicate
739   optional features implemented by the server and applicable to that
740   resource (e.g., Allow), possibly including extensions not defined by
741   this specification. The response body, if any, &SHOULD; also include
742   information about the communication options. The format for such a
743   body is not defined by this specification, but might be defined by
744   future extensions to HTTP. Content negotiation &MAY; be used to select
745   the appropriate response format. If no response body is included, the
746   response &MUST; include a Content-Length field with a field-value of
747   "0".
750   The Max-Forwards request-header field &MAY; be used to target a
751   specific proxy in the request chain. When a proxy receives an OPTIONS
752   request on an absoluteURI for which request forwarding is permitted,
753   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
754   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
755   instead, the proxy &SHOULD; respond with its own communication options.
756   If the Max-Forwards field-value is an integer greater than zero, the
757   proxy &MUST; decrement the field-value when it forwards the request. If
758   no Max-Forwards field is present in the request, then the forwarded
759   request &MUST-NOT; include a Max-Forwards field.
763<section title="GET" anchor="GET">
764  <rdf:Description>
765    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
766  </rdf:Description>
767  <iref primary="true" item="GET method" x:for-anchor=""/>
768  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
770   The GET method means retrieve whatever information (in the form of an
771   entity) is identified by the Request-URI. If the Request-URI refers
772   to a data-producing process, it is the produced data which shall be
773   returned as the entity in the response and not the source text of the
774   process, unless that text happens to be the output of the process.
777   The semantics of the GET method change to a "conditional GET" if the
778   request message includes an If-Modified-Since, If-Unmodified-Since,
779   If-Match, If-None-Match, or If-Range header field. A conditional GET
780   method requests that the entity be transferred only under the
781   circumstances described by the conditional header field(s). The
782   conditional GET method is intended to reduce unnecessary network
783   usage by allowing cached entities to be refreshed without requiring
784   multiple requests or transferring data already held by the client.
787   The semantics of the GET method change to a "partial GET" if the
788   request message includes a Range header field. A partial GET requests
789   that only part of the entity be transferred, as described in &header-range;.
790   The partial GET method is intended to reduce unnecessary
791   network usage by allowing partially-retrieved entities to be
792   completed without transferring data already held by the client.
795   The response to a GET request is cacheable if and only if it meets
796   the requirements for HTTP caching described in &caching;.
799   See <xref target=""/> for security considerations when used for forms.
803<section title="HEAD" anchor="HEAD">
804  <rdf:Description>
805    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
806  </rdf:Description>
807  <iref primary="true" item="HEAD method" x:for-anchor=""/>
808  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
810   The HEAD method is identical to GET except that the server &MUST-NOT;
811   return a message-body in the response. The metainformation contained
812   in the HTTP headers in response to a HEAD request &SHOULD; be identical
813   to the information sent in response to a GET request. This method can
814   be used for obtaining metainformation about the entity implied by the
815   request without transferring the entity-body itself. This method is
816   often used for testing hypertext links for validity, accessibility,
817   and recent modification.
820   The response to a HEAD request &MAY; be cacheable in the sense that the
821   information contained in the response &MAY; be used to update a
822   previously cached entity from that resource. If the new field values
823   indicate that the cached entity differs from the current entity (as
824   would be indicated by a change in Content-Length, Content-MD5, ETag
825   or Last-Modified), then the cache &MUST; treat the cache entry as
826   stale.
830<section title="POST" anchor="POST">
831  <iref primary="true" item="POST method" x:for-anchor=""/>
832  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
834   The POST method is used to request that the origin server accept the
835   entity enclosed in the request as data to be processed by the resource
836   identified by the Request-URI in the Request-Line. POST is designed
837   to allow a uniform method to cover the following functions:
838  <list style="symbols">
839    <t>
840      Annotation of existing resources;
841    </t>
842    <t>
843        Posting a message to a bulletin board, newsgroup, mailing list,
844        or similar group of articles;
845    </t>
846    <t>
847        Providing a block of data, such as the result of submitting a
848        form, to a data-handling process;
849    </t>
850    <t>
851        Extending a database through an append operation.
852    </t>
853  </list>
856   The actual function performed by the POST method is determined by the
857   server and is usually dependent on the Request-URI.
860   The action performed by the POST method might not result in a
861   resource that can be identified by a URI. In this case, either 200
862   (OK) or 204 (No Content) is the appropriate response status,
863   depending on whether or not the response includes an entity that
864   describes the result.
867   If a resource has been created on the origin server, the response
868   &SHOULD; be 201 (Created) and contain an entity which describes the
869   status of the request and refers to the new resource, and a Location
870   header (see <xref target="header.location"/>).
873   Responses to this method are not cacheable, unless the response
874   includes appropriate Cache-Control or Expires header fields. However,
875   the 303 (See Other) response can be used to direct the user agent to
876   retrieve a cacheable resource.
880<section title="PUT" anchor="PUT">
881  <iref primary="true" item="PUT method" x:for-anchor=""/>
882  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
884   The PUT method requests that the enclosed entity be stored at the
885   supplied Request-URI. If the Request-URI refers to an already
886   existing resource, the enclosed entity &SHOULD; be considered as a
887   modified version of the one residing on the origin server. If the
888   Request-URI does not point to an existing resource, and that URI is
889   capable of being defined as a new resource by the requesting user
890   agent, the origin server can create the resource with that URI. If a
891   new resource is created at the Request-URI, the origin server &MUST;
892         inform the user agent
893   via the 201 (Created) response. If an existing resource is modified,
894   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
895   to indicate successful completion of the request. If the resource
896   could not be created or modified with the Request-URI, an appropriate
897   error response &SHOULD; be given that reflects the nature of the
898   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
899   headers (headers starting with the prefix 'Content-') that it does
900   not understand or implement
901   and &MUST; return a 501 (Not Implemented) response in such cases.
904   If the request passes through a cache and the Request-URI identifies
905   one or more currently cached entities, those entries &SHOULD; be
906   treated as stale. Responses to this method are not cacheable.
909   The fundamental difference between the POST and PUT requests is
910   reflected in the different meaning of the Request-URI. The URI in a
911   POST request identifies the resource that will handle the enclosed
912   entity. That resource might be a data-accepting process, a gateway to
913   some other protocol, or a separate entity that accepts annotations.
914   In contrast, the URI in a PUT request identifies the entity enclosed
915   with the request -- the user agent knows what URI is intended and the
916   server &MUST-NOT; attempt to apply the request to some other resource.
917   If the server desires that the request be applied to a different URI,
918   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
919   then make its own decision regarding whether or not to redirect the
920   request.
923   A single resource &MAY; be identified by many different URIs. For
924   example, an article might have a URI for identifying "the current
925   version" which is separate from the URI identifying each particular
926   version. In this case, a PUT request on a general URI might result in
927   several other URIs being defined by the origin server.
930   HTTP/1.1 does not define how a PUT method affects the state of an
931   origin server.
934   Unless otherwise specified for a particular entity-header, the
935   entity-headers in the PUT request &SHOULD; be applied to the resource
936   created or modified by the PUT.
940<section title="DELETE" anchor="DELETE">
941  <iref primary="true" item="DELETE method" x:for-anchor=""/>
942  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
944   The DELETE method requests that the origin server delete the resource
945   identified by the Request-URI. This method &MAY; be overridden by human
946   intervention (or other means) on the origin server. The client cannot
947   be guaranteed that the operation has been carried out, even if the
948   status code returned from the origin server indicates that the action
949   has been completed successfully. However, the server &SHOULD-NOT;
950   indicate success unless, at the time the response is given, it
951   intends to delete the resource or move it to an inaccessible
952   location.
955   A successful response &SHOULD; be 200 (OK) if the response includes an
956   entity describing the status, 202 (Accepted) if the action has not
957   yet been enacted, or 204 (No Content) if the action has been enacted
958   but the response does not include an entity.
961   If the request passes through a cache and the Request-URI identifies
962   one or more currently cached entities, those entries &SHOULD; be
963   treated as stale. Responses to this method are not cacheable.
967<section title="TRACE" anchor="TRACE">
968  <rdf:Description>
969    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
970  </rdf:Description>
971  <iref primary="true" item="TRACE method" x:for-anchor=""/>
972  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
974   The TRACE method is used to invoke a remote, application-layer loop-back
975   of the request message. The final recipient of the request
976   &SHOULD; reflect the message received back to the client as the
977   entity-body of a 200 (OK) response. The final recipient is either the
978   origin server or the first proxy or gateway to receive a Max-Forwards
979   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
980   &MUST-NOT; include an entity.
983   TRACE allows the client to see what is being received at the other
984   end of the request chain and use that data for testing or diagnostic
985   information. The value of the Via header field (&header-via;) is of
986   particular interest, since it acts as a trace of the request chain.
987   Use of the Max-Forwards header field allows the client to limit the
988   length of the request chain, which is useful for testing a chain of
989   proxies forwarding messages in an infinite loop.
992   If the request is valid, the response &SHOULD; contain the entire
993   request message in the entity-body, with a Content-Type of
994   "message/http" (see &media-type-message-http;). Responses to this method
995   &MUST-NOT; be cached.
999<section title="CONNECT" anchor="CONNECT">
1000  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1001  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1003   This specification reserves the method name CONNECT for use with a
1004   proxy that can dynamically switch to being a tunnel (e.g. SSL
1005   tunneling <xref target="RFC2817"/>).
1011<section title="Status Code Definitions" anchor="">
1013   Each Status-Code is described below, including a description of which
1014   method(s) it can follow and any metainformation required in the
1015   response.
1018<section title="Informational 1xx" anchor="status.1xx">
1020   This class of status code indicates a provisional response,
1021   consisting only of the Status-Line and optional headers, and is
1022   terminated by an empty line. There are no required headers for this
1023   class of status code. Since HTTP/1.0 did not define any 1xx status
1024   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1025   except under experimental conditions.
1028   A client &MUST; be prepared to accept one or more 1xx status responses
1029   prior to a regular response, even if the client does not expect a 100
1030   (Continue) status message. Unexpected 1xx status responses &MAY; be
1031   ignored by a user agent.
1034   Proxies &MUST; forward 1xx responses, unless the connection between the
1035   proxy and its client has been closed, or unless the proxy itself
1036   requested the generation of the 1xx response. (For example, if a
1037   proxy adds a "Expect: 100-continue" field when it forwards a request,
1038   then it need not forward the corresponding 100 (Continue)
1039   response(s).)
1042<section title="100 Continue" anchor="status.100">
1043  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1044  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1046   The client &SHOULD; continue with its request. This interim response is
1047   used to inform the client that the initial part of the request has
1048   been received and has not yet been rejected by the server. The client
1049   &SHOULD; continue by sending the remainder of the request or, if the
1050   request has already been completed, ignore this response. The server
1051   &MUST; send a final response after the request has been completed. See
1052   &use100; for detailed discussion of the use and handling of this
1053   status code.
1057<section title="101 Switching Protocols" anchor="status.101">
1058  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1059  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1061   The server understands and is willing to comply with the client's
1062   request, via the Upgrade message header field (&header-upgrade;), for a
1063   change in the application protocol being used on this connection. The
1064   server will switch protocols to those defined by the response's
1065   Upgrade header field immediately after the empty line which
1066   terminates the 101 response.
1069   The protocol &SHOULD; be switched only when it is advantageous to do
1070   so. For example, switching to a newer version of HTTP is advantageous
1071   over older versions, and switching to a real-time, synchronous
1072   protocol might be advantageous when delivering resources that use
1073   such features.
1078<section title="Successful 2xx" anchor="status.2xx">
1080   This class of status code indicates that the client's request was
1081   successfully received, understood, and accepted.
1084<section title="200 OK" anchor="status.200">
1085  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1086  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1088   The request has succeeded. The information returned with the response
1089   is dependent on the method used in the request, for example:
1090  <list style="hanging">
1091    <t hangText="GET">
1092          an entity corresponding to the requested resource is sent in
1093          the response;
1094    </t>
1095    <t hangText="HEAD">
1096          the entity-header fields corresponding to the requested
1097          resource are sent in the response without any message-body;
1098    </t>
1099    <t hangText="POST">
1100      an entity describing or containing the result of the action;
1101    </t>
1102    <t hangText="TRACE">
1103      an entity containing the request message as received by the
1104      end server.
1105    </t>
1106  </list>
1110<section title="201 Created" anchor="status.201">
1111  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1112  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1114   The request has been fulfilled and resulted in a new resource being
1115   created. The newly created resource can be referenced by the URI(s)
1116   returned in the entity of the response, with the most specific URI
1117   for the resource given by a Location header field. The response
1118   &SHOULD; include an entity containing a list of resource
1119   characteristics and location(s) from which the user or user agent can
1120   choose the one most appropriate. The entity format is specified by
1121   the media type given in the Content-Type header field. The origin
1122   server &MUST; create the resource before returning the 201 status code.
1123   If the action cannot be carried out immediately, the server &SHOULD;
1124   respond with 202 (Accepted) response instead.
1127   A 201 response &MAY; contain an ETag response header field indicating
1128   the current value of the entity tag for the requested variant just
1129   created, see &header-etag;.
1133<section title="202 Accepted" anchor="status.202">
1134  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1135  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1137   The request has been accepted for processing, but the processing has
1138   not been completed.  The request might or might not eventually be
1139   acted upon, as it might be disallowed when processing actually takes
1140   place. There is no facility for re-sending a status code from an
1141   asynchronous operation such as this.
1144   The 202 response is intentionally non-committal. Its purpose is to
1145   allow a server to accept a request for some other process (perhaps a
1146   batch-oriented process that is only run once per day) without
1147   requiring that the user agent's connection to the server persist
1148   until the process is completed. The entity returned with this
1149   response &SHOULD; include an indication of the request's current status
1150   and either a pointer to a status monitor or some estimate of when the
1151   user can expect the request to be fulfilled.
1155<section title="203 Non-Authoritative Information" anchor="status.203">
1156  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1157  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1159   The returned metainformation in the entity-header is not the
1160   definitive set as available from the origin server, but is gathered
1161   from a local or a third-party copy. The set presented &MAY; be a subset
1162   or superset of the original version. For example, including local
1163   annotation information about the resource might result in a superset
1164   of the metainformation known by the origin server. Use of this
1165   response code is not required and is only appropriate when the
1166   response would otherwise be 200 (OK).
1170<section title="204 No Content" anchor="status.204">
1171  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1172  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1174   The server has fulfilled the request but does not need to return an
1175   entity-body, and might want to return updated metainformation. The
1176   response &MAY; include new or updated metainformation in the form of
1177   entity-headers, which if present &SHOULD; be associated with the
1178   requested variant.
1181   If the client is a user agent, it &SHOULD-NOT;  change its document view
1182   from that which caused the request to be sent. This response is
1183   primarily intended to allow input for actions to take place without
1184   causing a change to the user agent's active document view, although
1185   any new or updated metainformation &SHOULD; be applied to the document
1186   currently in the user agent's active view.
1189   The 204 response &MUST-NOT; include a message-body, and thus is always
1190   terminated by the first empty line after the header fields.
1194<section title="205 Reset Content" anchor="status.205">
1195  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1196  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1198   The server has fulfilled the request and the user agent &SHOULD; reset
1199   the document view which caused the request to be sent. This response
1200   is primarily intended to allow input for actions to take place via
1201   user input, followed by a clearing of the form in which the input is
1202   given so that the user can easily initiate another input action. The
1203   response &MUST-NOT; include an entity.
1207<section title="206 Partial Content" anchor="status.206">
1208  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1209  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1211   The server has fulfilled the partial GET request for the resource
1212   and the enclosed entity is a partial representation as defined in &range;.
1217<section title="Redirection 3xx" anchor="status.3xx">
1219   This class of status code indicates that further action needs to be
1220   taken by the user agent in order to fulfill the request.  The action
1221   required &MAY; be carried out by the user agent without interaction
1222   with the user if and only if the method used in the second request is
1223   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1224   such loops generate network traffic for each redirection.
1225  <list><t>
1226      <x:h>Note:</x:h> previous versions of this specification recommended a
1227      maximum of five redirections. Content developers should be aware
1228      that there might be clients that implement such a fixed
1229      limitation.
1230  </t></list>
1233<section title="300 Multiple Choices" anchor="status.300">
1234  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1235  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1237   The requested resource corresponds to any one of a set of
1238   representations, each with its own specific location, and agent-driven
1239   negotiation information (&content-negotiation;) is being provided so that
1240   the user (or user agent) can select a preferred representation and
1241   redirect its request to that location.
1244   Unless it was a HEAD request, the response &SHOULD; include an entity
1245   containing a list of resource characteristics and location(s) from
1246   which the user or user agent can choose the one most appropriate. The
1247   entity format is specified by the media type given in the Content-Type
1248   header field. Depending upon the format and the capabilities of
1249   the user agent, selection of the most appropriate choice &MAY; be
1250   performed automatically. However, this specification does not define
1251   any standard for such automatic selection.
1254   If the server has a preferred choice of representation, it &SHOULD;
1255   include the specific URI for that representation in the Location
1256   field; user agents &MAY; use the Location field value for automatic
1257   redirection. This response is cacheable unless indicated otherwise.
1261<section title="301 Moved Permanently" anchor="status.301">
1262  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1263  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1265   The requested resource has been assigned a new permanent URI and any
1266   future references to this resource &SHOULD; use one of the returned
1267   URIs.  Clients with link editing capabilities ought to automatically
1268   re-link references to the Request-URI to one or more of the new
1269   references returned by the server, where possible. This response is
1270   cacheable unless indicated otherwise.
1273   The new permanent URI &SHOULD; be given by the Location field in the
1274   response. Unless the request method was HEAD, the entity of the
1275   response &SHOULD; contain a short hypertext note with a hyperlink to
1276   the new URI(s).
1279   If the 301 status code is received in response to a request method
1280   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1281   then the request &MAY; be automatically redirected by the user agent without
1282   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1283   request unless it can be confirmed by the user, since this might
1284   change the conditions under which the request was issued.
1285  <list><t>
1286      <x:h>Note:</x:h> When automatically redirecting a POST request after
1287      receiving a 301 status code, some existing HTTP/1.0 user agents
1288      will erroneously change it into a GET request.
1289  </t></list>
1293<section title="302 Found" anchor="status.302">
1294  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1295  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1297   The requested resource resides temporarily under a different URI.
1298   Since the redirection might be altered on occasion, the client &SHOULD;
1299   continue to use the Request-URI for future requests.  This response
1300   is only cacheable if indicated by a Cache-Control or Expires header
1301   field.
1304   The temporary URI &SHOULD; be given by the Location field in the
1305   response. Unless the request method was HEAD, the entity of the
1306   response &SHOULD; contain a short hypertext note with a hyperlink to
1307   the new URI(s).
1310   If the 302 status code is received in response to a request method
1311   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1312   then the request &MAY; be automatically redirected by the user agent without
1313   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1314   request unless it can be confirmed by the user, since this might
1315   change the conditions under which the request was issued.
1316  <list><t>
1317      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1318      to change the method on the redirected request.  However, most
1319      existing user agent implementations treat 302 as if it were a 303
1320      response, performing a GET on the Location field-value regardless
1321      of the original request method. The status codes 303 and 307 have
1322      been added for servers that wish to make unambiguously clear which
1323      kind of reaction is expected of the client.
1324  </t></list>
1328<section title="303 See Other" anchor="status.303">
1329  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1330  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1332   The server directs the user agent to a different resource, indicated
1333   by a URI in the Location header field, that provides an indirect
1334   response to the original request.  The user agent &MAY; perform a GET
1335   request on the URI in the Location field in order to obtain a
1336   representation corresponding to the response, be redirected again,
1337   or end with an error status.  The Location URI is not a substitute
1338   reference for the originally requested resource.
1341   The 303 status is generally applicable to any HTTP method.  It is
1342   primarily used to allow the output of a POST action to redirect
1343   the user agent to a selected resource, since doing so provides the
1344   information corresponding to the POST response in a form that
1345   can be separately identified, bookmarked, and cached independent
1346   of the original request.
1349   A 303 response to a GET request indicates that the requested
1350   resource does not have a representation of its own that can be
1351   transferred by the server over HTTP.  The Location URI indicates a
1352   resource that is descriptive of the requested resource such that
1353   the follow-on representation may be useful without implying that
1354   it adequately represents the previously requested resource.
1355   Note that answers to the questions of what can be represented, what
1356   representations are adequate, and what might be a useful description
1357   are outside the scope of HTTP and thus entirely determined by the
1358   resource owner(s).
1361   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1362   cacheable by Cache-Control or Expires header fields.  Except for
1363   responses to a HEAD request, the entity of a 303 response &SHOULD;
1364   contain a short hypertext note with a hyperlink to the Location URI.
1368<section title="304 Not Modified" anchor="status.304">
1369  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1370  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1372   The response to the request has not been modified since the conditions
1373   indicated by the client's conditional GET request, as defined in &conditional;.
1377<section title="305 Use Proxy" anchor="status.305">
1378  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1379  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1381   The 305 status was defined in a previous version of this specification
1382   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1386<section title="306 (Unused)" anchor="status.306">
1387  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1388  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1390   The 306 status code was used in a previous version of the
1391   specification, is no longer used, and the code is reserved.
1395<section title="307 Temporary Redirect" anchor="status.307">
1396  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1397  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1399   The requested resource resides temporarily under a different URI.
1400   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1401   continue to use the Request-URI for future requests.  This response
1402   is only cacheable if indicated by a Cache-Control or Expires header
1403   field.
1406   The temporary URI &SHOULD; be given by the Location field in the
1407   response. Unless the request method was HEAD, the entity of the
1408   response &SHOULD; contain a short hypertext note with a hyperlink to
1409   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1410   understand the 307 status. Therefore, the note &SHOULD; contain the
1411   information necessary for a user to repeat the original request on
1412   the new URI.
1415   If the 307 status code is received in response to a request method
1416   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1417   then the request &MAY; be automatically redirected by the user agent without
1418   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1419   request unless it can be confirmed by the user, since this might
1420   change the conditions under which the request was issued.
1425<section title="Client Error 4xx" anchor="status.4xx">
1427   The 4xx class of status code is intended for cases in which the
1428   client seems to have erred. Except when responding to a HEAD request,
1429   the server &SHOULD; include an entity containing an explanation of the
1430   error situation, and whether it is a temporary or permanent
1431   condition. These status codes are applicable to any request method.
1432   User agents &SHOULD; display any included entity to the user.
1435   If the client is sending data, a server implementation using TCP
1436   &SHOULD; be careful to ensure that the client acknowledges receipt of
1437   the packet(s) containing the response, before the server closes the
1438   input connection. If the client continues sending data to the server
1439   after the close, the server's TCP stack will send a reset packet to
1440   the client, which may erase the client's unacknowledged input buffers
1441   before they can be read and interpreted by the HTTP application.
1444<section title="400 Bad Request" anchor="status.400">
1445  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1446  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1448   The request could not be understood by the server due to malformed
1449   syntax. The client &SHOULD-NOT;  repeat the request without
1450   modifications.
1454<section title="401 Unauthorized" anchor="status.401">
1455  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1456  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1458   The request requires user authentication (see &auth;).
1462<section title="402 Payment Required" anchor="status.402">
1463  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1464  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1466   This code is reserved for future use.
1470<section title="403 Forbidden" anchor="status.403">
1471  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1472  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1474   The server understood the request, but is refusing to fulfill it.
1475   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1476   If the request method was not HEAD and the server wishes to make
1477   public why the request has not been fulfilled, it &SHOULD; describe the
1478   reason for the refusal in the entity.  If the server does not wish to
1479   make this information available to the client, the status code 404
1480   (Not Found) can be used instead.
1484<section title="404 Not Found" anchor="status.404">
1485  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1486  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1488   The server has not found anything matching the Request-URI. No
1489   indication is given of whether the condition is temporary or
1490   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1491   knows, through some internally configurable mechanism, that an old
1492   resource is permanently unavailable and has no forwarding address.
1493   This status code is commonly used when the server does not wish to
1494   reveal exactly why the request has been refused, or when no other
1495   response is applicable.
1499<section title="405 Method Not Allowed" anchor="status.405">
1500  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1501  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1503   The method specified in the Request-Line is not allowed for the
1504   resource identified by the Request-URI. The response &MUST; include an
1505   Allow header containing a list of valid methods for the requested
1506   resource.
1510<section title="406 Not Acceptable" anchor="status.406">
1511  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1512  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1514   The resource identified by the request is only capable of generating
1515   response entities which have content characteristics not acceptable
1516   according to the accept headers sent in the request.
1519   Unless it was a HEAD request, the response &SHOULD; include an entity
1520   containing a list of available entity characteristics and location(s)
1521   from which the user or user agent can choose the one most
1522   appropriate. The entity format is specified by the media type given
1523   in the Content-Type header field. Depending upon the format and the
1524   capabilities of the user agent, selection of the most appropriate
1525   choice &MAY; be performed automatically. However, this specification
1526   does not define any standard for such automatic selection.
1527  <list><t>
1528      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1529      not acceptable according to the accept headers sent in the
1530      request. In some cases, this may even be preferable to sending a
1531      406 response. User agents are encouraged to inspect the headers of
1532      an incoming response to determine if it is acceptable.
1533  </t></list>
1536   If the response could be unacceptable, a user agent &SHOULD;
1537   temporarily stop receipt of more data and query the user for a
1538   decision on further actions.
1542<section title="407 Proxy Authentication Required" anchor="status.407">
1543  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1544  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1546   This code is similar to 401 (Unauthorized), but indicates that the
1547   client must first authenticate itself with the proxy (see &auth;).
1551<section title="408 Request Timeout" anchor="status.408">
1552  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1553  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1555   The client did not produce a request within the time that the server
1556   was prepared to wait. The client &MAY; repeat the request without
1557   modifications at any later time.
1561<section title="409 Conflict" anchor="status.409">
1562  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1563  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1565   The request could not be completed due to a conflict with the current
1566   state of the resource. This code is only allowed in situations where
1567   it is expected that the user might be able to resolve the conflict
1568   and resubmit the request. The response body &SHOULD; include enough
1569   information for the user to recognize the source of the conflict.
1570   Ideally, the response entity would include enough information for the
1571   user or user agent to fix the problem; however, that might not be
1572   possible and is not required.
1575   Conflicts are most likely to occur in response to a PUT request. For
1576   example, if versioning were being used and the entity being PUT
1577   included changes to a resource which conflict with those made by an
1578   earlier (third-party) request, the server might use the 409 response
1579   to indicate that it can't complete the request. In this case, the
1580   response entity would likely contain a list of the differences
1581   between the two versions in a format defined by the response
1582   Content-Type.
1586<section title="410 Gone" anchor="status.410">
1587  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1588  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1590   The requested resource is no longer available at the server and no
1591   forwarding address is known. This condition is expected to be
1592   considered permanent. Clients with link editing capabilities &SHOULD;
1593   delete references to the Request-URI after user approval. If the
1594   server does not know, or has no facility to determine, whether or not
1595   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1596   used instead. This response is cacheable unless indicated otherwise.
1599   The 410 response is primarily intended to assist the task of web
1600   maintenance by notifying the recipient that the resource is
1601   intentionally unavailable and that the server owners desire that
1602   remote links to that resource be removed. Such an event is common for
1603   limited-time, promotional services and for resources belonging to
1604   individuals no longer working at the server's site. It is not
1605   necessary to mark all permanently unavailable resources as "gone" or
1606   to keep the mark for any length of time -- that is left to the
1607   discretion of the server owner.
1611<section title="411 Length Required" anchor="status.411">
1612  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1613  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1615   The server refuses to accept the request without a defined Content-Length.
1616   The client &MAY; repeat the request if it adds a valid
1617   Content-Length header field containing the length of the message-body
1618   in the request message.
1622<section title="412 Precondition Failed" anchor="status.412">
1623  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1624  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1626   The precondition given in one or more of the request-header fields
1627   evaluated to false when it was tested on the server, as defined in
1628   &conditional;.
1632<section title="413 Request Entity Too Large" anchor="status.413">
1633  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1634  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1636   The server is refusing to process a request because the request
1637   entity is larger than the server is willing or able to process. The
1638   server &MAY; close the connection to prevent the client from continuing
1639   the request.
1642   If the condition is temporary, the server &SHOULD; include a Retry-After
1643   header field to indicate that it is temporary and after what
1644   time the client &MAY; try again.
1648<section title="414 Request-URI Too Long" anchor="status.414">
1649  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1650  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1652   The server is refusing to service the request because the Request-URI
1653   is longer than the server is willing to interpret. This rare
1654   condition is only likely to occur when a client has improperly
1655   converted a POST request to a GET request with long query
1656   information, when the client has descended into a URI "black hole" of
1657   redirection (e.g., a redirected URI prefix that points to a suffix of
1658   itself), or when the server is under attack by a client attempting to
1659   exploit security holes present in some servers using fixed-length
1660   buffers for reading or manipulating the Request-URI.
1664<section title="415 Unsupported Media Type" anchor="status.415">
1665  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1666  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1668   The server is refusing to service the request because the entity of
1669   the request is in a format not supported by the requested resource
1670   for the requested method.
1674<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1675  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1676  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1678   The request included a Range request-header field (&header-range;) and none of
1679   the range-specifier values in this field overlap the current extent
1680   of the selected resource.
1684<section title="417 Expectation Failed" anchor="status.417">
1685  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1686  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1688   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1689   could not be met by this server, or, if the server is a proxy,
1690   the server has unambiguous evidence that the request could not be met
1691   by the next-hop server.
1696<section title="Server Error 5xx" anchor="status.5xx">
1698   Response status codes beginning with the digit "5" indicate cases in
1699   which the server is aware that it has erred or is incapable of
1700   performing the request. Except when responding to a HEAD request, the
1701   server &SHOULD; include an entity containing an explanation of the
1702   error situation, and whether it is a temporary or permanent
1703   condition. User agents &SHOULD; display any included entity to the
1704   user. These response codes are applicable to any request method.
1707<section title="500 Internal Server Error" anchor="status.500">
1708  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1709  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1711   The server encountered an unexpected condition which prevented it
1712   from fulfilling the request.
1716<section title="501 Not Implemented" anchor="status.501">
1717  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1718  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1720   The server does not support the functionality required to fulfill the
1721   request. This is the appropriate response when the server does not
1722   recognize the request method and is not capable of supporting it for
1723   any resource.
1727<section title="502 Bad Gateway" anchor="status.502">
1728  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1729  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1731   The server, while acting as a gateway or proxy, received an invalid
1732   response from the upstream server it accessed in attempting to
1733   fulfill the request.
1737<section title="503 Service Unavailable" anchor="status.503">
1738  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1739  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1741   The server is currently unable to handle the request due to a
1742   temporary overloading or maintenance of the server. The implication
1743   is that this is a temporary condition which will be alleviated after
1744   some delay. If known, the length of the delay &MAY; be indicated in a
1745   Retry-After header. If no Retry-After is given, the client &SHOULD;
1746   handle the response as it would for a 500 response.
1747  <list><t>
1748      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1749      server must use it when becoming overloaded. Some servers may wish
1750      to simply refuse the connection.
1751  </t></list>
1755<section title="504 Gateway Timeout" anchor="status.504">
1756  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1757  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1759   The server, while acting as a gateway or proxy, did not receive a
1760   timely response from the upstream server specified by the URI (e.g.
1761   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1762   to access in attempting to complete the request.
1763  <list><t>
1764      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1765      return 400 or 500 when DNS lookups time out.
1766  </t></list>
1770<section title="505 HTTP Version Not Supported" anchor="status.505">
1771  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1772  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1774   The server does not support, or refuses to support, the protocol
1775   version that was used in the request message. The server is
1776   indicating that it is unable or unwilling to complete the request
1777   using the same major version as the client, as described in &http-version;,
1778   other than with this error message. The response &SHOULD; contain
1779   an entity describing why that version is not supported and what other
1780   protocols are supported by that server.
1788<section title="Header Field Definitions" anchor="header.fields">
1790   This section defines the syntax and semantics of HTTP/1.1 header fields
1791   related to request and response semantics.
1794   For entity-header fields, both sender and recipient refer to either the
1795   client or the server, depending on who sends and who receives the entity.
1798<section title="Allow" anchor="header.allow">
1799  <iref primary="true" item="Allow header" x:for-anchor=""/>
1800  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1801  <x:anchor-alias value="Allow"/>
1802  <x:anchor-alias value="Allow-v"/>
1804      The response-header field "Allow" lists the set of methods advertised as
1805      supported by the resource identified by the Request-URI. The purpose of
1806      this field is strictly to inform the recipient of valid methods
1807      associated with the resource. An Allow header field &MUST; be
1808      present in a 405 (Method Not Allowed) response.
1810<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1811  <x:ref>Allow</x:ref>   = "Allow" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1812  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1815      Example of use:
1817<figure><artwork type="example">
1818  Allow: GET, HEAD, PUT
1821      The actual set of allowed methods is defined
1822      by the origin server at the time of each request.
1825      A proxy &MUST-NOT; modify the Allow header field even if it does not
1826      understand all the methods specified, since the user agent might
1827      have other means of communicating with the origin server.
1831<section title="Expect" anchor="header.expect">
1832  <iref primary="true" item="Expect header" x:for-anchor=""/>
1833  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1834  <x:anchor-alias value="Expect"/>
1835  <x:anchor-alias value="Expect-v"/>
1836  <x:anchor-alias value="expectation"/>
1837  <x:anchor-alias value="expectation-extension"/>
1838  <x:anchor-alias value="expect-params"/>
1840   The request-header field "Expect" is used to indicate that particular
1841   server behaviors are required by the client.
1843<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1844  <x:ref>Expect</x:ref>       = "Expect" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1845  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1847  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1848  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1849                           *<x:ref>expect-params</x:ref> ]
1850  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1853   A server that does not understand or is unable to comply with any of
1854   the expectation values in the Expect field of a request &MUST; respond
1855   with appropriate error status. The server &MUST; respond with a 417
1856   (Expectation Failed) status if any of the expectations cannot be met
1857   or, if there are other problems with the request, some other 4xx
1858   status.
1861   This header field is defined with extensible syntax to allow for
1862   future extensions. If a server receives a request containing an
1863   Expect field that includes an expectation-extension that it does not
1864   support, it &MUST; respond with a 417 (Expectation Failed) status.
1867   Comparison of expectation values is case-insensitive for unquoted
1868   tokens (including the 100-continue token), and is case-sensitive for
1869   quoted-string expectation-extensions.
1872   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1873   return a 417 (Expectation Failed) status if it receives a request
1874   with an expectation that it cannot meet. However, the Expect
1875   request-header itself is end-to-end; it &MUST; be forwarded if the
1876   request is forwarded.
1879   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1880   Expect header.
1883   See &use100; for the use of the 100 (Continue) status.
1887<section title="From" anchor="header.from">
1888  <iref primary="true" item="From header" x:for-anchor=""/>
1889  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1890  <x:anchor-alias value="From"/>
1891  <x:anchor-alias value="From-v"/>
1892  <x:anchor-alias value="mailbox"/>
1894   The request-header field "From", if given, &SHOULD; contain an Internet
1895   e-mail address for the human user who controls the requesting user
1896   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1897   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1899<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1900  <x:ref>From</x:ref>    = "From" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1901  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1903  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1906   An example is:
1908<figure><artwork type="example">
1909  From:
1912   This header field &MAY; be used for logging purposes and as a means for
1913   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1914   be used as an insecure form of access protection. The interpretation
1915   of this field is that the request is being performed on behalf of the
1916   person given, who accepts responsibility for the method performed. In
1917   particular, robot agents &SHOULD; include this header so that the
1918   person responsible for running the robot can be contacted if problems
1919   occur on the receiving end.
1922   The Internet e-mail address in this field &MAY; be separate from the
1923   Internet host which issued the request. For example, when a request
1924   is passed through a proxy the original issuer's address &SHOULD; be
1925   used.
1928   The client &SHOULD-NOT;  send the From header field without the user's
1929   approval, as it might conflict with the user's privacy interests or
1930   their site's security policy. It is strongly recommended that the
1931   user be able to disable, enable, and modify the value of this field
1932   at any time prior to a request.
1936<section title="Location" anchor="header.location">
1937  <iref primary="true" item="Location header" x:for-anchor=""/>
1938  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1939  <x:anchor-alias value="Location"/>
1940  <x:anchor-alias value="Location-v"/>
1942   The response-header field "Location" is used for the identification of a
1943   new resource or to redirect the recipient to a location other than the
1944   Request-URI for completion of the request.  For 201 (Created)
1945   responses, the Location is that of the new resource which was created
1946   by the request. For 3xx responses, the location &SHOULD; indicate the
1947   server's preferred URI for automatic redirection to the resource. The
1948   field value consists of a single absolute URI.
1950<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1951  <x:ref>Location</x:ref>       = "Location" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1952  <x:ref>Location-v</x:ref>     = <x:ref>absoluteURI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1955   An example is:
1957<figure><artwork type="example">
1958  Location:
1961  <list><t>
1962      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1963      from Location in that the Content-Location identifies the original
1964      location of the entity enclosed in the response. It is therefore
1965      possible for a response to contain header fields for both Location
1966      and Content-Location.
1967  </t></list>
1970   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1971   <list style="symbols">
1972      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1973      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1974      <t>With 305 Use Proxy.</t>
1975   </list>
1979<section title="Max-Forwards" anchor="header.max-forwards">
1980  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1981  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1982  <x:anchor-alias value="Max-Forwards"/>
1983  <x:anchor-alias value="Max-Forwards-v"/>
1985   The request-header "Max-Forwards" field provides a mechanism with the
1986   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1987   number of proxies or gateways that can forward the request to the
1988   next inbound server. This can be useful when the client is attempting
1989   to trace a request chain which appears to be failing or looping in
1990   mid-chain.
1992<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
1993  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
1994  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
1997   The Max-Forwards value is a decimal integer indicating the remaining
1998   number of times this request message may be forwarded.
2001   Each proxy or gateway recipient of a TRACE or OPTIONS request
2002   containing a Max-Forwards header field &MUST; check and update its
2003   value prior to forwarding the request. If the received value is zero
2004   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2005   respond as the final recipient. If the received Max-Forwards value is
2006   greater than zero, then the forwarded message &MUST; contain an updated
2007   Max-Forwards field with a value decremented by one (1).
2010   The Max-Forwards header field &MAY; be ignored for all other methods
2011   defined by this specification and for any extension methods for which
2012   it is not explicitly referred to as part of that method definition.
2016<section title="Referer" anchor="header.referer">
2017  <iref primary="true" item="Referer header" x:for-anchor=""/>
2018  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2019  <x:anchor-alias value="Referer"/>
2020  <x:anchor-alias value="Referer-v"/>
2022   The request-header field "Referer" [sic] allows the client to specify,
2023   for the server's benefit, the address (URI) of the resource from
2024   which the Request-URI was obtained (the "referrer", although the
2025   header field is misspelled.) The Referer request-header allows a
2026   server to generate lists of back-links to resources for interest,
2027   logging, optimized caching, etc. It also allows obsolete or mistyped
2028   links to be traced for maintenance. The Referer field &MUST-NOT; be
2029   sent if the Request-URI was obtained from a source that does not have
2030   its own URI, such as input from the user keyboard.
2032<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2033  <x:ref>Referer</x:ref>        = "Referer" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2034  <x:ref>Referer-v</x:ref>      = <x:ref>absoluteURI</x:ref> / <x:ref>relativeURI</x:ref>
2037   Example:
2039<figure><artwork type="example">
2040  Referer:
2043   If the field value is a relative URI, it &SHOULD; be interpreted
2044   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
2045   <xref target=""/> for security considerations.
2049<section title="Retry-After" anchor="header.retry-after">
2050  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2051  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2052  <x:anchor-alias value="Retry-After"/>
2053  <x:anchor-alias value="Retry-After-v"/>
2055   The response-header "Retry-After" field can be used with a 503 (Service
2056   Unavailable) response to indicate how long the service is expected to
2057   be unavailable to the requesting client. This field &MAY; also be used
2058   with any 3xx (Redirection) response to indicate the minimum time the
2059   user-agent is asked wait before issuing the redirected request. The
2060   value of this field can be either an HTTP-date or an integer number
2061   of seconds (in decimal) after the time of the response.
2063<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2064  <x:ref>Retry-After</x:ref>   = "Retry-After" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2065  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2067<t anchor="">
2068  <x:anchor-alias value="delta-seconds"/>
2069   Time spans are non-negative decimal integers, representing time in
2070   seconds.
2072<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2073  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2076   Two examples of its use are
2078<figure><artwork type="example">
2079  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2080  Retry-After: 120
2083   In the latter example, the delay is 2 minutes.
2087<section title="Server" anchor="header.server">
2088  <iref primary="true" item="Server header" x:for-anchor=""/>
2089  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2090  <x:anchor-alias value="Server"/>
2091  <x:anchor-alias value="Server-v"/>
2093   The response-header field "Server" contains information about the
2094   software used by the origin server to handle the request. The field
2095   can contain multiple product tokens (&product-tokens;) and comments
2096   identifying the server and any significant subproducts. The product
2097   tokens are listed in order of their significance for identifying the
2098   application.
2100<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2101  <x:ref>Server</x:ref>         = "Server" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2102  <x:ref>Server-v</x:ref>       = 1*( <x:ref>product</x:ref> / <x:ref>comment</x:ref> )
2105   Example:
2107<figure><artwork type="example">
2108  Server: CERN/3.0 libwww/2.17
2111   If the response is being forwarded through a proxy, the proxy
2112   application &MUST-NOT; modify the Server response-header. Instead, it
2113   &MUST; include a Via field (as described in &header-via;).
2114  <list><t>
2115      <x:h>Note:</x:h> Revealing the specific software version of the server might
2116      allow the server machine to become more vulnerable to attacks
2117      against software that is known to contain security holes. Server
2118      implementors are encouraged to make this field a configurable
2119      option.
2120  </t></list>
2124<section title="User-Agent" anchor="header.user-agent">
2125  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2126  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2127  <x:anchor-alias value="User-Agent"/>
2128  <x:anchor-alias value="User-Agent-v"/>
2130   The request-header field "User-Agent" contains information about the
2131   user agent originating the request. This is for statistical purposes,
2132   the tracing of protocol violations, and automated recognition of user
2133   agents for the sake of tailoring responses to avoid particular user
2134   agent limitations. User agents &SHOULD; include this field with
2135   requests. The field can contain multiple product tokens (&product-tokens;)
2136   and comments identifying the agent and any subproducts which form a
2137   significant part of the user agent. By convention, the product tokens
2138   are listed in order of their significance for identifying the
2139   application.
2141<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2142  <x:ref>User-Agent</x:ref>     = "User-Agent" <x:ref>BWS</x:ref> ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2143  <x:ref>User-Agent-v</x:ref>   = 1*( <x:ref>product</x:ref> / <x:ref>comment</x:ref> )
2146   Example:
2148<figure><artwork type="example">
2149  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2155<section title="IANA Considerations" anchor="IANA.considerations">
2157<section title="Method Registry" anchor="method.registration">
2159  The registration procedure for HTTP Methods is defined by
2160  <xref target="method.registry"/> of this document.
2163   The HTTP Method Registry located at <eref target=""/>
2164   should be populated with the registrations below:
2166<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2167<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2168   <ttcol>Method</ttcol>
2169   <ttcol>Safe</ttcol>
2170   <ttcol>Reference</ttcol>
2171   <c>CONNECT</c>
2172   <c>no</c>
2173   <c>
2174      <xref target="CONNECT"/>
2175   </c>
2176   <c>DELETE</c>
2177   <c>no</c>
2178   <c>
2179      <xref target="DELETE"/>
2180   </c>
2181   <c>GET</c>
2182   <c>yes</c>
2183   <c>
2184      <xref target="GET"/>
2185   </c>
2186   <c>HEAD</c>
2187   <c>yes</c>
2188   <c>
2189      <xref target="HEAD"/>
2190   </c>
2191   <c>OPTIONS</c>
2192   <c>yes</c>
2193   <c>
2194      <xref target="OPTIONS"/>
2195   </c>
2196   <c>POST</c>
2197   <c>no</c>
2198   <c>
2199      <xref target="POST"/>
2200   </c>
2201   <c>PUT</c>
2202   <c>no</c>
2203   <c>
2204      <xref target="PUT"/>
2205   </c>
2206   <c>TRACE</c>
2207   <c>yes</c>
2208   <c>
2209      <xref target="TRACE"/>
2210   </c>
2215<section title="Status Code Registry" anchor="status.code.registration">
2217   The registration procedure for HTTP Status Codes -- previously defined
2218   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2219   by <xref target="status.code.registry"/> of this document.
2222   The HTTP Status Code Registry located at <eref target=""/>
2223   should be updated with the registrations below:
2225<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2226<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2227   <ttcol>Value</ttcol>
2228   <ttcol>Description</ttcol>
2229   <ttcol>Reference</ttcol>
2230   <c>100</c>
2231   <c>Continue</c>
2232   <c>
2233      <xref target="status.100"/>
2234   </c>
2235   <c>101</c>
2236   <c>Switching Protocols</c>
2237   <c>
2238      <xref target="status.101"/>
2239   </c>
2240   <c>200</c>
2241   <c>OK</c>
2242   <c>
2243      <xref target="status.200"/>
2244   </c>
2245   <c>201</c>
2246   <c>Created</c>
2247   <c>
2248      <xref target="status.201"/>
2249   </c>
2250   <c>202</c>
2251   <c>Accepted</c>
2252   <c>
2253      <xref target="status.202"/>
2254   </c>
2255   <c>203</c>
2256   <c>Non-Authoritative Information</c>
2257   <c>
2258      <xref target="status.203"/>
2259   </c>
2260   <c>204</c>
2261   <c>No Content</c>
2262   <c>
2263      <xref target="status.204"/>
2264   </c>
2265   <c>205</c>
2266   <c>Reset Content</c>
2267   <c>
2268      <xref target="status.205"/>
2269   </c>
2270   <c>206</c>
2271   <c>Partial Content</c>
2272   <c>
2273      <xref target="status.206"/>
2274   </c>
2275   <c>300</c>
2276   <c>Multiple Choices</c>
2277   <c>
2278      <xref target="status.300"/>
2279   </c>
2280   <c>301</c>
2281   <c>Moved Permanently</c>
2282   <c>
2283      <xref target="status.301"/>
2284   </c>
2285   <c>302</c>
2286   <c>Found</c>
2287   <c>
2288      <xref target="status.302"/>
2289   </c>
2290   <c>303</c>
2291   <c>See Other</c>
2292   <c>
2293      <xref target="status.303"/>
2294   </c>
2295   <c>304</c>
2296   <c>Not Modified</c>
2297   <c>
2298      <xref target="status.304"/>
2299   </c>
2300   <c>305</c>
2301   <c>Use Proxy</c>
2302   <c>
2303      <xref target="status.305"/>
2304   </c>
2305   <c>306</c>
2306   <c>(Unused)</c>
2307   <c>
2308      <xref target="status.306"/>
2309   </c>
2310   <c>307</c>
2311   <c>Temporary Redirect</c>
2312   <c>
2313      <xref target="status.307"/>
2314   </c>
2315   <c>400</c>
2316   <c>Bad Request</c>
2317   <c>
2318      <xref target="status.400"/>
2319   </c>
2320   <c>401</c>
2321   <c>Unauthorized</c>
2322   <c>
2323      <xref target="status.401"/>
2324   </c>
2325   <c>402</c>
2326   <c>Payment Required</c>
2327   <c>
2328      <xref target="status.402"/>
2329   </c>
2330   <c>403</c>
2331   <c>Forbidden</c>
2332   <c>
2333      <xref target="status.403"/>
2334   </c>
2335   <c>404</c>
2336   <c>Not Found</c>
2337   <c>
2338      <xref target="status.404"/>
2339   </c>
2340   <c>405</c>
2341   <c>Method Not Allowed</c>
2342   <c>
2343      <xref target="status.405"/>
2344   </c>
2345   <c>406</c>
2346   <c>Not Acceptable</c>
2347   <c>
2348      <xref target="status.406"/>
2349   </c>
2350   <c>407</c>
2351   <c>Proxy Authentication Required</c>
2352   <c>
2353      <xref target="status.407"/>
2354   </c>
2355   <c>408</c>
2356   <c>Request Timeout</c>
2357   <c>
2358      <xref target="status.408"/>
2359   </c>
2360   <c>409</c>
2361   <c>Conflict</c>
2362   <c>
2363      <xref target="status.409"/>
2364   </c>
2365   <c>410</c>
2366   <c>Gone</c>
2367   <c>
2368      <xref target="status.410"/>
2369   </c>
2370   <c>411</c>
2371   <c>Length Required</c>
2372   <c>
2373      <xref target="status.411"/>
2374   </c>
2375   <c>412</c>
2376   <c>Precondition Failed</c>
2377   <c>
2378      <xref target="status.412"/>
2379   </c>
2380   <c>413</c>
2381   <c>Request Entity Too Large</c>
2382   <c>
2383      <xref target="status.413"/>
2384   </c>
2385   <c>414</c>
2386   <c>Request-URI Too Long</c>
2387   <c>
2388      <xref target="status.414"/>
2389   </c>
2390   <c>415</c>
2391   <c>Unsupported Media Type</c>
2392   <c>
2393      <xref target="status.415"/>
2394   </c>
2395   <c>416</c>
2396   <c>Requested Range Not Satisfiable</c>
2397   <c>
2398      <xref target="status.416"/>
2399   </c>
2400   <c>417</c>
2401   <c>Expectation Failed</c>
2402   <c>
2403      <xref target="status.417"/>
2404   </c>
2405   <c>500</c>
2406   <c>Internal Server Error</c>
2407   <c>
2408      <xref target="status.500"/>
2409   </c>
2410   <c>501</c>
2411   <c>Not Implemented</c>
2412   <c>
2413      <xref target="status.501"/>
2414   </c>
2415   <c>502</c>
2416   <c>Bad Gateway</c>
2417   <c>
2418      <xref target="status.502"/>
2419   </c>
2420   <c>503</c>
2421   <c>Service Unavailable</c>
2422   <c>
2423      <xref target="status.503"/>
2424   </c>
2425   <c>504</c>
2426   <c>Gateway Timeout</c>
2427   <c>
2428      <xref target="status.504"/>
2429   </c>
2430   <c>505</c>
2431   <c>HTTP Version Not Supported</c>
2432   <c>
2433      <xref target="status.505"/>
2434   </c>
2438<section title="Message Header Registration" anchor="message.header.registration">
2440   The Message Header Registry located at <eref target=""/> should be updated
2441   with the permanent registrations below (see <xref target="RFC3864"/>):
2443<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2444<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2445   <ttcol>Header Field Name</ttcol>
2446   <ttcol>Protocol</ttcol>
2447   <ttcol>Status</ttcol>
2448   <ttcol>Reference</ttcol>
2449   <c>Allow</c>
2450   <c>http</c>
2451   <c>standard</c>
2452   <c>
2453      <xref target="header.allow"/>
2454   </c>
2455   <c>Expect</c>
2456   <c>http</c>
2457   <c>standard</c>
2458   <c>
2459      <xref target="header.expect"/>
2460   </c>
2461   <c>From</c>
2462   <c>http</c>
2463   <c>standard</c>
2464   <c>
2465      <xref target="header.from"/>
2466   </c>
2467   <c>Location</c>
2468   <c>http</c>
2469   <c>standard</c>
2470   <c>
2471      <xref target="header.location"/>
2472   </c>
2473   <c>Max-Forwards</c>
2474   <c>http</c>
2475   <c>standard</c>
2476   <c>
2477      <xref target="header.max-forwards"/>
2478   </c>
2479   <c>Referer</c>
2480   <c>http</c>
2481   <c>standard</c>
2482   <c>
2483      <xref target="header.referer"/>
2484   </c>
2485   <c>Retry-After</c>
2486   <c>http</c>
2487   <c>standard</c>
2488   <c>
2489      <xref target="header.retry-after"/>
2490   </c>
2491   <c>Server</c>
2492   <c>http</c>
2493   <c>standard</c>
2494   <c>
2495      <xref target="header.server"/>
2496   </c>
2497   <c>User-Agent</c>
2498   <c>http</c>
2499   <c>standard</c>
2500   <c>
2501      <xref target="header.user-agent"/>
2502   </c>
2506   The change controller is: "IETF ( - Internet Engineering Task Force".
2511<section title="Security Considerations" anchor="security.considerations">
2513   This section is meant to inform application developers, information
2514   providers, and users of the security limitations in HTTP/1.1 as
2515   described by this document. The discussion does not include
2516   definitive solutions to the problems revealed, though it does make
2517   some suggestions for reducing security risks.
2520<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2522   Like any generic data transfer protocol, HTTP cannot regulate the
2523   content of the data that is transferred, nor is there any a priori
2524   method of determining the sensitivity of any particular piece of
2525   information within the context of any given request. Therefore,
2526   applications &SHOULD; supply as much control over this information as
2527   possible to the provider of that information. Four header fields are
2528   worth special mention in this context: Server, Via, Referer and From.
2531   Revealing the specific software version of the server might allow the
2532   server machine to become more vulnerable to attacks against software
2533   that is known to contain security holes. Implementors &SHOULD; make the
2534   Server header field a configurable option.
2537   Proxies which serve as a portal through a network firewall &SHOULD;
2538   take special precautions regarding the transfer of header information
2539   that identifies the hosts behind the firewall. In particular, they
2540   &SHOULD; remove, or replace with sanitized versions, any Via fields
2541   generated behind the firewall.
2544   The Referer header allows reading patterns to be studied and reverse
2545   links drawn. Although it can be very useful, its power can be abused
2546   if user details are not separated from the information contained in
2547   the Referer. Even when the personal information has been removed, the
2548   Referer header might indicate a private document's URI whose
2549   publication would be inappropriate.
2552   The information sent in the From field might conflict with the user's
2553   privacy interests or their site's security policy, and hence it
2554   &SHOULD-NOT;  be transmitted without the user being able to disable,
2555   enable, and modify the contents of the field. The user &MUST; be able
2556   to set the contents of this field within a user preference or
2557   application defaults configuration.
2560   We suggest, though do not require, that a convenient toggle interface
2561   be provided for the user to enable or disable the sending of From and
2562   Referer information.
2565   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2566   fields can sometimes be used to determine that a specific client or
2567   server have a particular security hole which might be exploited.
2568   Unfortunately, this same information is often used for other valuable
2569   purposes for which HTTP currently has no better mechanism.
2573<section title="Encoding Sensitive Information in URIs" anchor="">
2575   Because the source of a link might be private information or might
2576   reveal an otherwise private information source, it is strongly
2577   recommended that the user be able to select whether or not the
2578   Referer field is sent. For example, a browser client could have a
2579   toggle switch for browsing openly/anonymously, which would
2580   respectively enable/disable the sending of Referer and From
2581   information.
2584   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2585   HTTP request if the referring page was transferred with a secure
2586   protocol.
2589   Authors of services should not use
2590   GET-based forms for the submission of sensitive data because that
2591   data will be encoded in the Request-URI. Many existing
2592   servers, proxies, and user agents log or display the Request-URI in
2593   places where it might be visible to third parties. Such services can
2594   use POST-based form submission instead.
2598<section title="Location Headers and Spoofing" anchor="location.spoofing">
2600   If a single server supports multiple organizations that do not trust
2601   one another, then it &MUST; check the values of Location and Content-Location
2602   headers in responses that are generated under control of
2603   said organizations to make sure that they do not attempt to
2604   invalidate resources over which they have no authority.
2610<section title="Acknowledgments" anchor="ack">
2615<references title="Normative References">
2617<reference anchor="Part1">
2618  <front>
2619    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2620    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2621      <organization abbrev="Day Software">Day Software</organization>
2622      <address><email></email></address>
2623    </author>
2624    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2625      <organization>One Laptop per Child</organization>
2626      <address><email></email></address>
2627    </author>
2628    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2629      <organization abbrev="HP">Hewlett-Packard Company</organization>
2630      <address><email></email></address>
2631    </author>
2632    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2633      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2634      <address><email></email></address>
2635    </author>
2636    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2637      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2638      <address><email></email></address>
2639    </author>
2640    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2641      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2642      <address><email></email></address>
2643    </author>
2644    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2645      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2646      <address><email></email></address>
2647    </author>
2648    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2649      <organization abbrev="W3C">World Wide Web Consortium</organization>
2650      <address><email></email></address>
2651    </author>
2652    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2653      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2654      <address><email></email></address>
2655    </author>
2656    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2657  </front>
2658  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2659  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2662<reference anchor="Part3">
2663  <front>
2664    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2665    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2666      <organization abbrev="Day Software">Day Software</organization>
2667      <address><email></email></address>
2668    </author>
2669    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2670      <organization>One Laptop per Child</organization>
2671      <address><email></email></address>
2672    </author>
2673    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2674      <organization abbrev="HP">Hewlett-Packard Company</organization>
2675      <address><email></email></address>
2676    </author>
2677    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2678      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2679      <address><email></email></address>
2680    </author>
2681    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2682      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2683      <address><email></email></address>
2684    </author>
2685    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2686      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2687      <address><email></email></address>
2688    </author>
2689    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2690      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2691      <address><email></email></address>
2692    </author>
2693    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2694      <organization abbrev="W3C">World Wide Web Consortium</organization>
2695      <address><email></email></address>
2696    </author>
2697    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2698      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2699      <address><email></email></address>
2700    </author>
2701    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2702  </front>
2703  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2704  <x:source href="p3-payload.xml" basename="p3-payload"/>
2707<reference anchor="Part4">
2708  <front>
2709    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2710    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2711      <organization abbrev="Day Software">Day Software</organization>
2712      <address><email></email></address>
2713    </author>
2714    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2715      <organization>One Laptop per Child</organization>
2716      <address><email></email></address>
2717    </author>
2718    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2719      <organization abbrev="HP">Hewlett-Packard Company</organization>
2720      <address><email></email></address>
2721    </author>
2722    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2723      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2724      <address><email></email></address>
2725    </author>
2726    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2727      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2728      <address><email></email></address>
2729    </author>
2730    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2731      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2732      <address><email></email></address>
2733    </author>
2734    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2735      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2736      <address><email></email></address>
2737    </author>
2738    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2739      <organization abbrev="W3C">World Wide Web Consortium</organization>
2740      <address><email></email></address>
2741    </author>
2742    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2743      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2744      <address><email></email></address>
2745    </author>
2746    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2747  </front>
2748  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2749  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2752<reference anchor="Part5">
2753  <front>
2754    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2755    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2756      <organization abbrev="Day Software">Day Software</organization>
2757      <address><email></email></address>
2758    </author>
2759    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2760      <organization>One Laptop per Child</organization>
2761      <address><email></email></address>
2762    </author>
2763    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2764      <organization abbrev="HP">Hewlett-Packard Company</organization>
2765      <address><email></email></address>
2766    </author>
2767    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2768      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2769      <address><email></email></address>
2770    </author>
2771    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2772      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2773      <address><email></email></address>
2774    </author>
2775    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2776      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2777      <address><email></email></address>
2778    </author>
2779    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2780      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2781      <address><email></email></address>
2782    </author>
2783    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2784      <organization abbrev="W3C">World Wide Web Consortium</organization>
2785      <address><email></email></address>
2786    </author>
2787    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2788      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2789      <address><email></email></address>
2790    </author>
2791    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2792  </front>
2793  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2794  <x:source href="p5-range.xml" basename="p5-range"/>
2797<reference anchor="Part6">
2798  <front>
2799    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2800    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2801      <organization abbrev="Day Software">Day Software</organization>
2802      <address><email></email></address>
2803    </author>
2804    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2805      <organization>One Laptop per Child</organization>
2806      <address><email></email></address>
2807    </author>
2808    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2809      <organization abbrev="HP">Hewlett-Packard Company</organization>
2810      <address><email></email></address>
2811    </author>
2812    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2813      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2814      <address><email></email></address>
2815    </author>
2816    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2817      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2818      <address><email></email></address>
2819    </author>
2820    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2821      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2822      <address><email></email></address>
2823    </author>
2824    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2825      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2826      <address><email></email></address>
2827    </author>
2828    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2829      <organization abbrev="W3C">World Wide Web Consortium</organization>
2830      <address><email></email></address>
2831    </author>
2832    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2833      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2834      <address><email></email></address>
2835    </author>
2836    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2837  </front>
2838  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2839  <x:source href="p6-cache.xml" basename="p6-cache"/>
2842<reference anchor="Part7">
2843  <front>
2844    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2845    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2846      <organization abbrev="Day Software">Day Software</organization>
2847      <address><email></email></address>
2848    </author>
2849    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2850      <organization>One Laptop per Child</organization>
2851      <address><email></email></address>
2852    </author>
2853    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2854      <organization abbrev="HP">Hewlett-Packard Company</organization>
2855      <address><email></email></address>
2856    </author>
2857    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2858      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2859      <address><email></email></address>
2860    </author>
2861    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2862      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2863      <address><email></email></address>
2864    </author>
2865    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2866      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2867      <address><email></email></address>
2868    </author>
2869    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2870      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2871      <address><email></email></address>
2872    </author>
2873    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2874      <organization abbrev="W3C">World Wide Web Consortium</organization>
2875      <address><email></email></address>
2876    </author>
2877    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2878      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2879      <address><email></email></address>
2880    </author>
2881    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2882  </front>
2883  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2884  <x:source href="p7-auth.xml" basename="p7-auth"/>
2887<reference anchor="RFC2119">
2888  <front>
2889    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2890    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2891      <organization>Harvard University</organization>
2892      <address><email></email></address>
2893    </author>
2894    <date month="March" year="1997"/>
2895  </front>
2896  <seriesInfo name="BCP" value="14"/>
2897  <seriesInfo name="RFC" value="2119"/>
2902<references title="Informative References">
2904<reference anchor="RFC1945">
2905  <front>
2906    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2907    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2908      <organization>MIT, Laboratory for Computer Science</organization>
2909      <address><email></email></address>
2910    </author>
2911    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2912      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2913      <address><email></email></address>
2914    </author>
2915    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2916      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2917      <address><email></email></address>
2918    </author>
2919    <date month="May" year="1996"/>
2920  </front>
2921  <seriesInfo name="RFC" value="1945"/>
2924<reference anchor="RFC2068">
2925  <front>
2926    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2927    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2928      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2929      <address><email></email></address>
2930    </author>
2931    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2932      <organization>MIT Laboratory for Computer Science</organization>
2933      <address><email></email></address>
2934    </author>
2935    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2936      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2937      <address><email></email></address>
2938    </author>
2939    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2940      <organization>MIT Laboratory for Computer Science</organization>
2941      <address><email></email></address>
2942    </author>
2943    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2944      <organization>MIT Laboratory for Computer Science</organization>
2945      <address><email></email></address>
2946    </author>
2947    <date month="January" year="1997"/>
2948  </front>
2949  <seriesInfo name="RFC" value="2068"/>
2952<reference anchor="RFC2616">
2953  <front>
2954    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2955    <author initials="R." surname="Fielding" fullname="R. Fielding">
2956      <organization>University of California, Irvine</organization>
2957      <address><email></email></address>
2958    </author>
2959    <author initials="J." surname="Gettys" fullname="J. Gettys">
2960      <organization>W3C</organization>
2961      <address><email></email></address>
2962    </author>
2963    <author initials="J." surname="Mogul" fullname="J. Mogul">
2964      <organization>Compaq Computer Corporation</organization>
2965      <address><email></email></address>
2966    </author>
2967    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2968      <organization>MIT Laboratory for Computer Science</organization>
2969      <address><email></email></address>
2970    </author>
2971    <author initials="L." surname="Masinter" fullname="L. Masinter">
2972      <organization>Xerox Corporation</organization>
2973      <address><email></email></address>
2974    </author>
2975    <author initials="P." surname="Leach" fullname="P. Leach">
2976      <organization>Microsoft Corporation</organization>
2977      <address><email></email></address>
2978    </author>
2979    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2980      <organization>W3C</organization>
2981      <address><email></email></address>
2982    </author>
2983    <date month="June" year="1999"/>
2984  </front>
2985  <seriesInfo name="RFC" value="2616"/>
2988<reference anchor='RFC2817'>
2989  <front>
2990    <title>Upgrading to TLS Within HTTP/1.1</title>
2991    <author initials='R.' surname='Khare' fullname='R. Khare'>
2992      <organization>4K Associates / UC Irvine</organization>
2993      <address><email></email></address>
2994    </author>
2995    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
2996      <organization>Agranat Systems, Inc.</organization>
2997      <address><email></email></address>
2998    </author>
2999    <date year='2000' month='May' />
3000  </front>
3001  <seriesInfo name='RFC' value='2817' />
3004<reference anchor='RFC3864'>
3005  <front>
3006    <title>Registration Procedures for Message Header Fields</title>
3007    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3008      <organization>Nine by Nine</organization>
3009      <address><email></email></address>
3010    </author>
3011    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3012      <organization>BEA Systems</organization>
3013      <address><email></email></address>
3014    </author>
3015    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3016      <organization>HP Labs</organization>
3017      <address><email></email></address>
3018    </author>
3019    <date year='2004' month='September' />
3020  </front>
3021  <seriesInfo name='BCP' value='90' />
3022  <seriesInfo name='RFC' value='3864' />
3025<reference anchor='RFC5226'>
3026  <front>
3027    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3028    <author initials='T.' surname='Narten' fullname='T. Narten'>
3029      <organization>IBM</organization>
3030      <address><email></email></address>
3031    </author>
3032    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3033      <organization>Google</organization>
3034      <address><email></email></address>
3035    </author>
3036    <date year='2008' month='May' />
3037  </front>
3038  <seriesInfo name='BCP' value='26' />
3039  <seriesInfo name='RFC' value='5226' />
3042<reference anchor="RFC5322">
3043  <front>
3044    <title>Internet Message Format</title>
3045    <author initials="P." surname="Resnick" fullname="P. Resnick">
3046      <organization>Qualcomm Incorporated</organization>
3047    </author>
3048    <date year="2008" month="October"/>
3049  </front>
3050  <seriesInfo name="RFC" value="5322"/>
3055<section title="Compatibility with Previous Versions" anchor="compatibility">
3056<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3058   Clarified which error code should be used for inbound server failures
3059   (e.g. DNS failures). (<xref target="status.504"/>).
3062   201 (Created) had a race that required an Etag be sent when a resource is
3063   first created. (<xref target="status.201"/>).
3066   Rewrite of message transmission requirements to make it much harder
3067   for implementors to get it wrong, as the consequences of errors here
3068   can have significant impact on the Internet, and to deal with the
3069   following problems:
3070  <list style="numbers">
3071      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3072         this was incorrectly placing a requirement on the behavior of
3073         an implementation of a future version of HTTP/1.x</t>
3075      <t>Made it clear that user-agents should retry requests, not
3076         "clients" in general.</t>
3078      <t>Converted requirements for clients to ignore unexpected 100
3079         (Continue) responses, and for proxies to forward 100 responses,
3080         into a general requirement for 1xx responses.</t>
3082      <t>Modified some TCP-specific language, to make it clearer that
3083         non-TCP transports are possible for HTTP.</t>
3085      <t>Require that the origin server &MUST-NOT; wait for the request
3086         body before it sends a required 100 (Continue) response.</t>
3088      <t>Allow, rather than require, a server to omit 100 (Continue) if
3089         it has already seen some of the request body.</t>
3091      <t>Allow servers to defend against denial-of-service attacks and
3092         broken clients.</t>
3093  </list>
3096   This change adds the Expect header and 417 status code.
3099   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3100   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3103   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
3104   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3108<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3110  This document takes over the Status Code Registry, previously defined
3111  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3112  (<xref target="status.code.registry"/>)
3115  Clarify definition of POST.
3116  (<xref target="POST"/>)
3119  Failed to consider that there are
3120  many other request methods that are safe to automatically redirect,
3121  and further that the user agent is able to make that determination
3122  based on the request method semantics.
3123  (Sections <xref format="counter" target="status.301"/>,
3124  <xref format="counter" target="status.302"/> and
3125  <xref format="counter" target="status.307"/>)
3128  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3129  It used to indicate that the requested resource must be accessed through the
3130  proxy given by the Location field. The Location field gave the URI of the
3131  proxy. The recipient was expected to repeat this single request via the proxy.
3132  (<xref target="status.305"/>)
3135  Reclassify Allow header as response header, removing the option to
3136  specify it in a PUT request.
3137  Relax the server requirement on the contents of the Allow header and
3138  remove requirement on clients to always trust the header value.
3139  (<xref target="header.allow"/>)
3142  Correct syntax of Location header to allow fragment,
3143  as referred symbol wasn't what was expected, and add some
3144  clarifications as to when it would not be appropriate.
3145  (<xref target="header.location"/>)
3148  In the description of the Server header, the Via field
3149  was described as a SHOULD. The requirement was and is stated
3150  correctly in the description of the Via header in &header-via;.
3151  (<xref target="header.server"/>)
3157<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3159<section title="Since RFC2616">
3161  Extracted relevant partitions from <xref target="RFC2616"/>.
3165<section title="Since draft-ietf-httpbis-p2-semantics-00">
3167  Closed issues:
3168  <list style="symbols">
3169    <t>
3170      <eref target=""/>:
3171      "Via is a MUST"
3172      (<eref target=""/>)
3173    </t>
3174    <t>
3175      <eref target=""/>:
3176      "Fragments allowed in Location"
3177      (<eref target=""/>)
3178    </t>
3179    <t>
3180      <eref target=""/>:
3181      "Safe Methods vs Redirection"
3182      (<eref target=""/>)
3183    </t>
3184    <t>
3185      <eref target=""/>:
3186      "Revise description of the POST method"
3187      (<eref target=""/>)
3188    </t>
3189    <t>
3190      <eref target=""/>:
3191      "Normative and Informative references"
3192    </t>
3193    <t>
3194      <eref target=""/>:
3195      "RFC2606 Compliance"
3196    </t>
3197    <t>
3198      <eref target=""/>:
3199      "Informative references"
3200    </t>
3201    <t>
3202      <eref target=""/>:
3203      "Redundant cross-references"
3204    </t>
3205  </list>
3208  Other changes:
3209  <list style="symbols">
3210    <t>
3211      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3212    </t>
3213  </list>
3217<section title="Since draft-ietf-httpbis-p2-semantics-01">
3219  Closed issues:
3220  <list style="symbols">
3221    <t>
3222      <eref target=""/>:
3223      "PUT side effects"
3224    </t>
3225    <t>
3226      <eref target=""/>:
3227      "Duplicate Host header requirements"
3228    </t>
3229  </list>
3232  Ongoing work on ABNF conversion (<eref target=""/>):
3233  <list style="symbols">
3234    <t>
3235      Move "Product Tokens" section (back) into Part 1, as "token" is used
3236      in the definition of the Upgrade header.
3237    </t>
3238    <t>
3239      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3240    </t>
3241    <t>
3242      Copy definition of delta-seconds from Part6 instead of referencing it.
3243    </t>
3244  </list>
3248<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3250  Closed issues:
3251  <list style="symbols">
3252    <t>
3253      <eref target=""/>:
3254      "Requiring Allow in 405 responses"
3255    </t>
3256    <t>
3257      <eref target=""/>:
3258      "Status Code Registry"
3259    </t>
3260    <t>
3261      <eref target=""/>:
3262      "Redirection vs. Location"
3263    </t>
3264    <t>
3265      <eref target=""/>:
3266      "Cacheability of 303 response"
3267    </t>
3268    <t>
3269      <eref target=""/>:
3270      "305 Use Proxy"
3271    </t>
3272    <t>
3273      <eref target=""/>:
3274      "Classification for Allow header"
3275    </t>
3276    <t>
3277      <eref target=""/>:
3278      "PUT - 'store under' vs 'store at'"
3279    </t>
3280  </list>
3283  Ongoing work on IANA Message Header Registration (<eref target=""/>):
3284  <list style="symbols">
3285    <t>
3286      Reference RFC 3984, and update header registrations for headers defined
3287      in this document.
3288    </t>
3289  </list>
3292  Ongoing work on ABNF conversion (<eref target=""/>):
3293  <list style="symbols">
3294    <t>
3295      Replace string literals when the string really is case-sensitive (method).
3296    </t>
3297  </list>
3301<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3303  Closed issues:
3304  <list style="symbols">
3305    <t>
3306      <eref target=""/>:
3307      "OPTIONS request bodies"
3308    </t>
3309    <t>
3310      <eref target=""/>:
3311      "Description of CONNECT should refer to RFC2817"
3312    </t>
3313    <t>
3314      <eref target=""/>:
3315      "Location Content-Location reference request/response mixup"
3316    </t>
3317  </list>
3320  Ongoing work on Method Registry (<eref target=""/>):
3321  <list style="symbols">
3322    <t>
3323      Added initial proposal for registration process, plus initial
3324      content (non-HTTP/1.1 methods to be added by a separate specification).
3325    </t>
3326  </list>
3330<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3332  Closed issues:
3333  <list style="symbols">
3334    <t>
3335      <eref target=""/>:
3336      "Content-*"
3337    </t>
3338    <t>
3339      <eref target=""/>:
3340      "RFC 2822 is updated by RFC 5322"
3341    </t>
3342  </list>
3345  Ongoing work on ABNF conversion (<eref target=""/>):
3346  <list style="symbols">
3347    <t>
3348      Use "/" instead of "|" for alternatives.
3349    </t>
3350    <t>
3351      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3352      whitespace ("OWS") and required whitespace ("RWS").
3353    </t>
3354    <t>
3355      Rewrite ABNFs to spell out whitespace rules, factor out
3356      header value format definitions.
3357    </t>
3358  </list>
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