source: draft-ietf-httpbis/14/p2-semantics.xml @ 1271

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[29]1<?xml version="1.0" encoding="utf-8"?>
[101]2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
[8]3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns=''>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns=''>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns=''>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns=''>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns=''>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns=''>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns=''>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns=''>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns=''>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns=''>SHOULD NOT</bcp14>">
[1271]14  <!ENTITY ID-VERSION "14">
[1254]15  <!ENTITY ID-MONTH "April">
[1099]16  <!ENTITY ID-YEAR "2011">
[1101]17  <!ENTITY mdash "&#8212;">
[424]18  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x=''/>">
[31]19  <!ENTITY messaging                  "<xref target='Part1' xmlns:x=''/>">
20  <!ENTITY payload                    "<xref target='Part3' xmlns:x=''/>">
21  <!ENTITY conditional                "<xref target='Part4' xmlns:x=''/>">
22  <!ENTITY range                      "<xref target='Part5' xmlns:x=''/>">
23  <!ENTITY caching                    "<xref target='Part6' xmlns:x=''/>">
24  <!ENTITY auth                       "<xref target='Part7' xmlns:x=''/>">
[994]25  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' xmlns:x=''/>">
[31]26  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x=''/>">
[205]27  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
28  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
[31]29  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
[823]30  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x=''/>">
[580]31  <!ENTITY full-date                  "<xref target='Part1' x:rel='' xmlns:x=''/>">
[31]32  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
33  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
34  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
35  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
[1065]36  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x=''/>">
[31]37  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
38  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
39  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
40  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
41  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
42  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
43  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
44  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
45  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
46  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
47  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
48  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
[688]49  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x=''/>">
[31]50  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
51  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
52  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
53  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
54  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
55  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
56  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
57  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
58  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
59  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
[835]60  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
61  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x=''/>">
[31]62  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
63  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
64  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
65  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
66  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
[190]67  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
[263]68  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='' xmlns:x=''/>">
[700]69  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x=''/>">
70  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x=''/>">
71  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x=''/>">
72  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x=''/>">
73  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x=''/>">
74  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x=''/>">
[838]75  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x=''/>">
76  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x=''/>">
77  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x=''/>">
[1050]78  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x=''/>">
[1111]79  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x=''/>">
80  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x=''/>">
82<?rfc toc="yes" ?>
[29]83<?rfc symrefs="yes" ?>
84<?rfc sortrefs="yes" ?>
[8]85<?rfc compact="yes"?>
86<?rfc subcompact="no" ?>
87<?rfc linkmailto="no" ?>
88<?rfc editing="no" ?>
[203]89<?rfc comments="yes"?>
90<?rfc inline="yes"?>
[799]91<?rfc rfcedstyle="yes"?>
[8]92<?rfc-ext allow-markup-in-artwork="yes" ?>
93<?rfc-ext include-references-in-index="yes" ?>
[308]94<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
[446]95     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
[286]96     xmlns:x=''
97     xmlns:rdf=''>
[120]100  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
[29]102  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]103    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[8]104    <address>
105      <postal>
[1106]106        <street>345 Park Ave</street>
107        <city>San Jose</city>
[8]108        <region>CA</region>
[1106]109        <code>95110</code>
[29]110        <country>USA</country>
[8]111      </postal>
[29]112      <email></email>
113      <uri></uri>
[8]114    </address>
115  </author>
[29]117  <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]118    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
[8]119    <address>
120      <postal>
[29]121        <street>21 Oak Knoll Road</street>
122        <city>Carlisle</city>
[8]123        <region>MA</region>
[29]124        <code>01741</code>
125        <country>USA</country>
[8]126      </postal>
[844]127      <email></email>
128      <uri></uri>
[8]129    </address>
130  </author>
132  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
[29]133    <organization abbrev="HP">Hewlett-Packard Company</organization>
[8]134    <address>
135      <postal>
[29]136        <street>HP Labs, Large Scale Systems Group</street>
137        <street>1501 Page Mill Road, MS 1177</street>
[8]138        <city>Palo Alto</city>
139        <region>CA</region>
[29]140        <code>94304</code>
141        <country>USA</country>
[8]142      </postal>
[29]143      <email></email>
[8]144    </address>
145  </author>
147  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
[29]148    <organization abbrev="Microsoft">Microsoft Corporation</organization>
[8]149    <address>
150      <postal>
[29]151        <street>1 Microsoft Way</street>
152        <city>Redmond</city>
153        <region>WA</region>
154        <code>98052</code>
155        <country>USA</country>
[8]156      </postal>
[29]157      <email></email>
[8]158    </address>
159  </author>
161  <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]162    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[8]163    <address>
164      <postal>
[29]165        <street>345 Park Ave</street>
166        <city>San Jose</city>
[8]167        <region>CA</region>
[29]168        <code>95110</code>
169        <country>USA</country>
[8]170      </postal>
[29]171      <email></email>
172      <uri></uri>
[8]173    </address>
174  </author>
176  <author initials="P." surname="Leach" fullname="Paul J. Leach">
177    <organization abbrev="Microsoft">Microsoft Corporation</organization>
178    <address>
179      <postal>
180        <street>1 Microsoft Way</street>
181        <city>Redmond</city>
182        <region>WA</region>
183        <code>98052</code>
184      </postal>
185      <email></email>
186    </address>
187  </author>
189  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
190    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
191    <address>
192      <postal>
[34]193        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
194        <street>The Stata Center, Building 32</street>
195        <street>32 Vassar Street</street>
[8]196        <city>Cambridge</city>
197        <region>MA</region>
198        <code>02139</code>
[29]199        <country>USA</country>
[8]200      </postal>
201      <email></email>
[34]202      <uri></uri>
[8]203    </address>
204  </author>
[95]206  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
[94]207    <organization abbrev="W3C">World Wide Web Consortium</organization>
208    <address>
209      <postal>
210        <street>W3C / ERCIM</street>
211        <street>2004, rte des Lucioles</street>
212        <city>Sophia-Antipolis</city>
213        <region>AM</region>
214        <code>06902</code>
215        <country>France</country>
216      </postal>
217      <email></email>
218      <uri></uri>
219    </address>
220  </author>
[95]222  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
223    <organization abbrev="greenbytes">greenbytes GmbH</organization>
224    <address>
225      <postal>
226        <street>Hafenweg 16</street>
227        <city>Muenster</city><region>NW</region><code>48155</code>
228        <country>Germany</country>
229      </postal>
[609]230      <phone>+49 251 2807760</phone>
231      <facsimile>+49 251 2807761</facsimile>
232      <email></email>
233      <uri></uri>
[95]234    </address>
235  </author>
[1271]237  <date month="&ID-MONTH;" year="&ID-YEAR;" day="18"/>
[440]238  <workgroup>HTTPbis Working Group</workgroup>
242   The Hypertext Transfer Protocol (HTTP) is an application-level
243   protocol for distributed, collaborative, hypermedia information
[29]244   systems. HTTP has been in use by the World Wide Web global information
[35]245   initiative since 1990. This document is Part 2 of the seven-part specification
[29]246   that defines the protocol referred to as "HTTP/1.1" and, taken together,
[42]247   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
[1163]248   as expressed by request methods, request header fields, response status codes,
249   and response header fields.
253<note title="Editorial Note (To be removed by RFC Editor)">
254  <t>
255    Discussion of this draft should take place on the HTTPBIS working group
[1268]256    mailing list (, which is archived at
257    <eref target=""/>.
258  </t>
259  <t>
260    The current issues list is at
261    <eref target=""/> and related
262    documents (including fancy diffs) can be found at
[324]263    <eref target=""/>.
[36]264  </t>
[153]265  <t>
[1180]266    The changes in this draft are summarized in <xref target="changes.since.13"/>.
[153]267  </t>
271<section title="Introduction" anchor="introduction">
[162]273   This document defines HTTP/1.1 request and response semantics.  Each HTTP
274   message, as defined in &messaging;, is in the form of either a request or
275   a response.  An HTTP server listens on a connection for HTTP requests and
276   responds to each request, in the order received on that connection, with
277   one or more HTTP response messages.  This document defines the commonly
278   agreed upon semantics of the HTTP uniform interface, the intentions defined
279   by each request method, and the various response messages that might be
[965]280   expected as a result of applying that method to the target resource.
[162]283   This document is currently disorganized in order to minimize the changes
284   between drafts and enable reviewers to see the smaller errata changes.
[980]285   A future draft will reorganize the sections to better reflect the content.
[162]286   In particular, the sections will be ordered according to the typical
287   processing of an HTTP request message (after message parsing): resource
[1163]288   mapping, methods, request modifying header fields, response status,
289   status modifying header fields, and resource metadata.  The current mess
290   reflects how widely dispersed these topics and associated requirements
291   had become in <xref target="RFC2616"/>.
294<section title="Requirements" anchor="intro.requirements">
296   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
297   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
298   document are to be interpreted as described in <xref target="RFC2119"/>.
301   An implementation is not compliant if it fails to satisfy one or more
[847]302   of the "MUST" or "REQUIRED" level requirements for the protocols it
303   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
304   level and all the "SHOULD" level requirements for its protocols is said
305   to be "unconditionally compliant"; one that satisfies all the "MUST"
306   level requirements but not all the "SHOULD" level requirements for its
307   protocols is said to be "conditionally compliant".
[424]311<section title="Syntax Notation" anchor="notation">
[425]312  <x:anchor-alias value="CR"/>
313  <x:anchor-alias value="DIGIT"/>
314  <x:anchor-alias value="LF"/>
315  <x:anchor-alias value="VCHAR"/>
316  <x:anchor-alias value="WSP"/>
[543]318  This specification uses the ABNF syntax defined in &notation; (which
319  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
320  <xref target="collected.abnf"/> shows the collected ABNF, with the list
321  rule expanded.
[425]324  The following core rules are included by
325  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
326  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
327  DIGIT (decimal 0-9), DQUOTE (double quote),
328  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
329  OCTET (any 8-bit sequence of data), SP (space),
330  VCHAR (any visible USASCII character),
331  and WSP (whitespace).
334<section title="Core Rules" anchor="core.rules">
[398]335  <x:anchor-alias value="obs-text"/>
[229]336  <x:anchor-alias value="quoted-string"/>
337  <x:anchor-alias value="token"/>
[356]338  <x:anchor-alias value="OWS"/>
339  <x:anchor-alias value="RWS"/>
[424]341  The core rules below are defined in &basic-rules;:
343<figure><artwork type="abnf2616">
[229]344  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
345  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
[356]346  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
347  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
[398]348  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
352<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
[374]353  <x:anchor-alias value="absolute-URI"/>
[688]354  <x:anchor-alias value="comment"/>
[229]355  <x:anchor-alias value="HTTP-date"/>
[391]356  <x:anchor-alias value="partial-URI"/>
[229]357  <x:anchor-alias value="product"/>
[785]358  <x:anchor-alias value="URI-reference"/>
[206]360  The ABNF rules below are defined in other parts:
[207]362<figure><!--Part1--><artwork type="abnf2616">
[374]363  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
[688]364  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
[229]365  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
[391]366  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
[229]367  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
[785]368  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
[8]374<section title="Method" anchor="method">
[229]375  <x:anchor-alias value="Method"/>
376  <x:anchor-alias value="extension-method"/>
[1161]378   The Method token indicates the request method to be performed on the target
[972]379   resource (&effective-request-uri;). The method is case-sensitive.
[1128]381<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
382  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
385   The list of methods allowed by a resource can be specified in an
[965]386   Allow header field (<xref target="header.allow"/>). The status code of the response
[8]387   always notifies the client whether a method is currently allowed on a
388   resource, since the set of allowed methods can change dynamically. An
[965]389   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
[8]390   if the method is known by the origin server but not allowed for the
[965]391   resource, and 501 (Not Implemented) if the method is
[8]392   unrecognized or not implemented by the origin server. The methods GET
393   and HEAD &MUST; be supported by all general-purpose servers. All other
394   methods are &OPTIONAL;; however, if the above methods are implemented,
395   they &MUST; be implemented with the same semantics as those specified
396   in <xref target="method.definitions"/>.
[1128]399<section title="Overview of Methods" anchor="overview.of.methods">
401  The methods listed below are defined in <xref target="method.definitions"/>.
403<texttable align="left">
404  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
406  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
407  <c>GET</c> <c><xref target="GET"/></c>
408  <c>HEAD</c> <c><xref target="HEAD"/></c>
409  <c>POST</c> <c><xref target="POST"/></c>
410  <c>PUT</c> <c><xref target="PUT"/></c>
411  <c>DELETE</c> <c><xref target="DELETE"/></c>
412  <c>TRACE</c> <c><xref target="TRACE"/></c>
413  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
[1161]416  Note that this list is not exhaustive &mdash; it does not include request methods defined
[1128]417  in other specifications.
[270]421<section title="Method Registry" anchor="method.registry">
423  The HTTP Method Registry defines the name space for the Method token in the
424  Request line of an HTTP request.
[286]427  Registrations &MUST; include the following fields:
428  <list style="symbols">
429    <t>Method Name (see <xref target="method"/>)</t>
430    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
431    <t>Pointer to specification text</t>
432  </list>
[270]435  Values to be added to this name space are subject to IETF review
[591]436  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
[672]439  The registry itself is maintained at <eref target=""/>.
[1037]442<section title="Considerations for New Methods" anchor="">
444   When it is necessary to express new semantics for a HTTP request that
445   aren't specific to a single application or media type, and currently defined
446   methods are inadequate, it may be appropriate to register a new method.
[1042]449   HTTP methods are generic; that is, they are potentially applicable to any
450   resource, not just one particular media type, "type" of resource, or
451   application. As such, it is preferred that new HTTP methods be registered
452   in a document that isn't specific to a single application, so that this is
453   clear.
[1040]456   Due to the parsing rules defined in &message-body;, definitions of HTTP
457   methods cannot prohibit the presence of a message-body on either the request
458   or the response message (with responses to HEAD requests being the single
459   exception). Definitions of new methods cannot change this rule, but they can
460   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
[1042]463   New method definitions need to indicate whether they are safe (<xref
[1261]464   target="safe.methods"/>), what semantics (if any) the request body has,
465   and whether they are idempotent (<xref target="idempotent.methods"/>).
466   They also need to state whether they can be cached (&caching;); in
467   particular what conditions a cache may store the response, and under what
468   conditions such a stored response may be used to satisfy a subsequent
469   request.
476<section title="Request Header Fields" anchor="request.header.fields">
[229]477  <x:anchor-alias value="request-header"/>
[1163]479   The request header fields allow the client to pass additional
[8]480   information about the request, and about the client itself, to the
481   server. These fields act as request modifiers, with semantics
482   equivalent to the parameters on a programming language method
483   invocation.
[1138]485<texttable align="left">
486  <ttcol>Header Field Name</ttcol>
487  <ttcol>Defined in...</ttcol>
489  <c>Accept</c> <c>&header-accept;</c>
490  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
491  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
492  <c>Accept-Language</c> <c>&header-accept-language;</c>
493  <c>Authorization</c> <c>&header-authorization;</c>
494  <c>Expect</c> <c><xref target="header.expect"/></c>
495  <c>From</c> <c><xref target="header.from"/></c>
496  <c>Host</c> <c>&header-host;</c>
497  <c>If-Match</c> <c>&header-if-match;</c>
498  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
499  <c>If-None-Match</c> <c>&header-if-none-match;</c>
500  <c>If-Range</c> <c>&header-if-range;</c>
501  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
502  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
503  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
504  <c>Range</c> <c>&header-range;</c>
505  <c>Referer</c> <c><xref target="header.referer"/></c>
506  <c>TE</c> <c>&header-te;</c>
507  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
511<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
[229]512  <x:anchor-alias value="Reason-Phrase"/>
513  <x:anchor-alias value="Status-Code"/>
[426]514  <x:anchor-alias value="extension-code"/>
[1124]516   The Status-Code element is a 3-digit integer result code of the attempt to
517   understand and satisfy the request.
[1124]520   The Reason-Phrase is intended to give a short textual description of the
[1137]521   Status-Code and is intended for a human user. The client does not need
[1124]522   to examine or display the Reason-Phrase.
524<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"/>
[1124]525  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
[398]526  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
529   HTTP status codes are extensible. HTTP applications are not required
530   to understand the meaning of all registered status codes, though such
531   understanding is obviously desirable. However, applications &MUST;
532   understand the class of any status code, as indicated by the first
533   digit, and treat any unrecognized response as being equivalent to the
534   x00 status code of that class, with the exception that an
535   unrecognized response &MUST-NOT; be cached. For example, if an
536   unrecognized status code of 431 is received by the client, it can
537   safely assume that there was something wrong with its request and
538   treat the response as if it had received a 400 status code. In such
[866]539   cases, user agents &SHOULD; present to the user the representation enclosed
540   with the response, since that representation is likely to include human-readable
[8]541   information which will explain the unusual status.
[1124]544<section title="Overview of Status Codes" anchor="">
[1137]546   The status codes listed below are defined in <xref target=""/>
547   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
548   The reason phrases listed here are only recommendations &mdash; they can be
549   replaced by local equivalents without affecting the protocol.
551<texttable align="left">
552  <ttcol>Status-Code</ttcol>
553  <ttcol>Reason-Phrase</ttcol>
554  <ttcol>Defined in...</ttcol>
556  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
557  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
559  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
560  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
561  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
562  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
563  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
564  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
565  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
567  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
568  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
569  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
570  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
571  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
572  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
573  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
575  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
576  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
577  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
578  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
579  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
580  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
581  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
582  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
583  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
584  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
585  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
586  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
587  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
588  <c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
589  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
590  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
591  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
592  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
593  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
595  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
596  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
597  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
598  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
599  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
600  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
603   Note that this list is not exhaustive &mdash; it does not include
604   extension status codes defined in other specifications.
[262]608<section title="Status Code Registry" anchor="status.code.registry">
610  The HTTP Status Code Registry defines the name space for the Status-Code
[924]611  token in the Status-Line of an HTTP response.
614  Values to be added to this name space are subject to IETF review
[591]615  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
618  The registry itself is maintained at <eref target=""/>.
[1038]621<section title="Considerations for New Status Codes" anchor="">
623   When it is necessary to express new semantics for a HTTP response that
624   aren't specific to a single application or media type, and currently defined
625   status codes are inadequate, a new status code can be registered.
[1043]628   HTTP status codes are generic; that is, they are potentially applicable to
629   any resource, not just one particular media type, "type" of resource, or
630   application. As such, it is preferred that new HTTP status codes be
631   registered in a document that isn't specific to a single application, so
632   that this is clear.
[1043]635   Definitions of new HTTP status codes typically explain the request
636   conditions that produce a response containing the status code (e.g.,
637   combinations of request headers and/or method(s)), along with any
638   interactions with response headers (e.g., those that are required, those
639   that modify the semantics of the response).
642   New HTTP status codes are required to fall under one of the categories
643   defined in <xref target=""/>. To allow existing parsers to
644   properly handle them, new status codes cannot disallow a response body,
645   although they can mandate a zero-length response body. They can require the
646   presence of one or more particular HTTP response header(s).
649   Likewise, their definitions can specify that caches are allowed to use
[1035]650   heuristics to determine their freshness (see &caching;; by default, it is
[1043]651   not allowed), and can define how to determine the resource which they
[1035]652   carry a representation for (see <xref
653   target="identifying.response.associated.with.representation"/>; by default,
[1038]654   it is anonymous).
[8]662<section title="Response Header Fields" anchor="response.header.fields">
[229]663  <x:anchor-alias value="response-header"/>
[1163]665   The response header fields allow the server to pass additional
[8]666   information about the response which cannot be placed in the Status-Line.
667   These header fields give information about the server and about
[972]668   further access to the target resource (&effective-request-uri;).
[1138]670<texttable align="left">
[1163]671  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
673  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
674  <c>Age</c> <c>&header-age;</c>
675  <c>Allow</c> <c><xref target="header.allow"/></c>
676  <c>ETag</c> <c>&header-etag;</c>
677  <c>Location</c> <c><xref target="header.location"/></c>
678  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
679  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
680  <c>Server</c> <c><xref target="header.server"/></c>
681  <c>Vary</c> <c>&header-vary;</c>
682  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
[874]686<section title="Representation" anchor="representation">
[866]688   Request and Response messages &MAY; transfer a representation if not otherwise
689   restricted by the request method or response status code. A representation
690   consists of metadata (representation header fields) and data (representation
691   body).  When a complete or partial representation is enclosed in an HTTP message,
692   it is referred to as the payload of the message. HTTP representations
693   are defined in &payload;.
[866]696   A representation body is only present in a message when a message-body is
697   present, as described in &message-body;. The representation body is obtained
[8]698   from the message-body by decoding any Transfer-Encoding that might
699   have been applied to ensure safe and proper transfer of the message.
702<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
[965]704   It is sometimes necessary to determine an identifier for the resource
[695]705   associated with a representation.
708   An HTTP request representation, when present, is always associated with an
709   anonymous (i.e., unidentified) resource.
[972]712   In the common case, an HTTP response is a representation of the target
713   resource (see &effective-request-uri;). However, this is not always the
714   case. To determine the URI of the resource a response is associated with,
715   the following rules are used (with the first applicable one being selected):
717<t><list style="numbers">
718   <t>If the response status code is 200 or 203 and the request method was GET,
[972]719   the response payload is a representation of the target resource.</t>
[924]720   <t>If the response status code is 204, 206, or 304 and the request method was GET
[972]721   or HEAD, the response payload is a partial representation of the target
[1079]722   resource (see &combining-responses;).</t>
[994]723   <t>If the response has a Content-Location header field, and that URI is the same
[965]724   as the effective request URI, the response payload is a representation of the
[972]725   target resource.</t>
[994]726   <t>If the response has a Content-Location header field, and that URI is not the
[965]727   same as the effective request URI, then the response asserts that its
728   payload is a representation of the resource identified by the
729   Content-Location URI. However, such an assertion cannot be trusted unless
730   it can be verified by other means (not defined by HTTP).</t>
[695]731   <t>Otherwise, the response is a representation of an anonymous (i.e.,
732   unidentified) resource.</t>
735  <cref anchor="TODO-req-uri">
[823]736   The comparison function is going to have to be defined somewhere,
[695]737   because we already need to compare URIs for things like cache invalidation.</cref>
[8]744<section title="Method Definitions" anchor="method.definitions">
[1161]746   The set of common request methods for HTTP/1.1 is defined below. Although
[8]747   this set can be expanded, additional methods cannot be assumed to
748   share the same semantics for separately extended clients and servers.
751<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
753<section title="Safe Methods" anchor="safe.methods">
[286]754<iref item="Safe Methods" primary="true"/>
[969]756   Implementors need to be aware that the software represents the user in
757   their interactions over the Internet, and need to allow
[901]758   the user to be aware of any actions they take which might have an
[8]759   unexpected significance to themselves or others.
[708]762   In particular, the convention has been established that the GET, HEAD,
[1161]763   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
764   of taking an action other than retrieval. These request methods ought
765   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
[8]766   This allows user agents to represent other methods, such as POST, PUT
767   and DELETE, in a special way, so that the user is made aware of the
768   fact that a possibly unsafe action is being requested.
771   Naturally, it is not possible to ensure that the server does not
772   generate side-effects as a result of performing a GET request; in
773   fact, some dynamic resources consider that a feature. The important
774   distinction here is that the user did not request the side-effects,
775   so therefore cannot be held accountable for them.
779<section title="Idempotent Methods" anchor="idempotent.methods">
[286]780<iref item="Idempotent Methods" primary="true"/>
[1161]782   Request methods can also have the property of "idempotence" in that,
783   aside from error or expiration issues, the intended effect of multiple
[657]784   identical requests is the same as for a single request.
[1161]785   PUT, DELETE, and all safe request methods are idempotent.
[657]786   It is important to note that idempotence refers only to changes
787   requested by the client: a server is free to change its state due
788   to multiple requests for the purpose of tracking those requests,
789   versioning of results, etc.
794<section title="OPTIONS" anchor="OPTIONS">
[286]795  <rdf:Description>
796    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
797  </rdf:Description>
[8]798  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
799  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
[1161]801   The OPTIONS method requests information about the
[8]802   communication options available on the request/response chain
[1161]803   identified by the effective request URI. This method allows a client to
[8]804   determine the options and/or requirements associated with a resource,
805   or the capabilities of a server, without implying a resource action
806   or initiating a resource retrieval.
[1161]809   Responses to the OPTIONS method are not cacheable.
[874]812   If the OPTIONS request includes a message-body (as indicated by the
[8]813   presence of Content-Length or Transfer-Encoding), then the media type
814   &MUST; be indicated by a Content-Type field. Although this
815   specification does not define any use for such a body, future
816   extensions to HTTP might use the OPTIONS body to make more detailed
[280]817   queries on the server.
[391]820   If the request-target is an asterisk ("*"), the OPTIONS request is
[8]821   intended to apply to the server in general rather than to a specific
822   resource. Since a server's communication options typically depend on
823   the resource, the "*" request is only useful as a "ping" or "no-op"
824   type of method; it does nothing beyond allowing the client to test
825   the capabilities of the server. For example, this can be used to test
826   a proxy for HTTP/1.1 compliance (or lack thereof).
[391]829   If the request-target is not an asterisk, the OPTIONS request applies
[8]830   only to the options that are available when communicating with that
831   resource.
834   A 200 response &SHOULD; include any header fields that indicate
835   optional features implemented by the server and applicable to that
836   resource (e.g., Allow), possibly including extensions not defined by
837   this specification. The response body, if any, &SHOULD; also include
838   information about the communication options. The format for such a
839   body is not defined by this specification, but might be defined by
840   future extensions to HTTP. Content negotiation &MAY; be used to select
841   the appropriate response format. If no response body is included, the
842   response &MUST; include a Content-Length field with a field-value of
843   "0".
[1163]846   The Max-Forwards header field &MAY; be used to target a
[893]847   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
848   If no Max-Forwards field is present in the request, then the forwarded
[8]849   request &MUST-NOT; include a Max-Forwards field.
853<section title="GET" anchor="GET">
[286]854  <rdf:Description>
855    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
856  </rdf:Description>
[8]857  <iref primary="true" item="GET method" x:for-anchor=""/>
858  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
[1161]860   The GET method requests transfer of a current representation of
861   the target resource.
[972]864   If the target resource is a data-producing process, it is the
[866]865   produced data which shall be returned as the representation in the response and not
[730]866   the source text of the process, unless that text happens to be the output of
867   the process.
870   The semantics of the GET method change to a "conditional GET" if the
871   request message includes an If-Modified-Since, If-Unmodified-Since,
872   If-Match, If-None-Match, or If-Range header field. A conditional GET
[1161]873   requests that the representation be transferred only under the
[8]874   circumstances described by the conditional header field(s). The
[1161]875   conditional GET request is intended to reduce unnecessary network
[874]876   usage by allowing cached representations to be refreshed without requiring
[8]877   multiple requests or transferring data already held by the client.
880   The semantics of the GET method change to a "partial GET" if the
881   request message includes a Range header field. A partial GET requests
[866]882   that only part of the representation be transferred, as described in &header-range;.
[1161]883   The partial GET request is intended to reduce unnecessary
[866]884   network usage by allowing partially-retrieved representations to be
[8]885   completed without transferring data already held by the client.
888   Bodies on GET requests have no defined semantics. Note that sending a body
889   on a GET request might cause some existing implementations to reject the
890   request.
[888]893   The response to a GET request is cacheable and &MAY; be used to satisfy
894   subsequent GET and HEAD requests (see &caching;).
897   See <xref target=""/> for security considerations when used for forms.
901<section title="HEAD" anchor="HEAD">
[286]902  <rdf:Description>
903    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
904  </rdf:Description>
[8]905  <iref primary="true" item="HEAD method" x:for-anchor=""/>
906  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
908   The HEAD method is identical to GET except that the server &MUST-NOT;
[867]909   return a message-body in the response. The metadata contained
[994]910   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
[8]911   to the information sent in response to a GET request. This method can
[867]912   be used for obtaining metadata about the representation implied by the
[866]913   request without transferring the representation body. This method is
[8]914   often used for testing hypertext links for validity, accessibility,
915   and recent modification.
[888]918   The response to a HEAD request is cacheable and &MAY; be used to satisfy
919   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
920   representation from that resource; if the new field values
[874]921   indicate that the cached representation differs from the current representation (as
[8]922   would be indicated by a change in Content-Length, Content-MD5, ETag
923   or Last-Modified), then the cache &MUST; treat the cache entry as
924   stale.
927   Bodies on HEAD requests have no defined semantics. Note that sending a body
928   on a HEAD request might cause some existing implementations to reject the
929   request.
933<section title="POST" anchor="POST">
934  <iref primary="true" item="POST method" x:for-anchor=""/>
935  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
[1161]937   The POST method requests that the origin server accept the
[972]938   representation enclosed in the request as data to be processed by the
939   target resource. POST is designed to allow a uniform method to cover the
940   following functions:
[8]941  <list style="symbols">
942    <t>
943      Annotation of existing resources;
944    </t>
945    <t>
946        Posting a message to a bulletin board, newsgroup, mailing list,
947        or similar group of articles;
948    </t>
949    <t>
950        Providing a block of data, such as the result of submitting a
951        form, to a data-handling process;
952    </t>
953    <t>
954        Extending a database through an append operation.
955    </t>
956  </list>
959   The actual function performed by the POST method is determined by the
[965]960   server and is usually dependent on the effective request URI.
963   The action performed by the POST method might not result in a
964   resource that can be identified by a URI. In this case, either 200
[924]965   (OK) or 204 (No Content) is the appropriate response status code,
[874]966   depending on whether or not the response includes a representation that
[8]967   describes the result.
970   If a resource has been created on the origin server, the response
[874]971   &SHOULD; be 201 (Created) and contain a representation which describes the
[8]972   status of the request and refers to the new resource, and a Location
[994]973   header field (see <xref target="header.location"/>).
[910]976   Responses to POST requests are only cacheable when they
977   include explicit freshness information (see &p6-explicit;). A
[994]978   cached POST response with a Content-Location header field
[972]979   (see &header-content-location;) whose value is the effective
[910]980   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
983   Note that POST caching is not widely implemented.
[888]984   However, the 303 (See Other) response can be used to direct the
985   user agent to retrieve a cacheable resource.
989<section title="PUT" anchor="PUT">
990  <iref primary="true" item="PUT method" x:for-anchor=""/>
991  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
[1161]993   The PUT method requests that the state of the target resource
[1158]994   be created or replaced with the state defined by the representation
995   enclosed in the request message payload.  A successful PUT of a given
996   representation would suggest that a subsequent GET on that same target
997   resource will result in an equivalent representation being returned in
998   a 200 (OK) response.  However, there is no guarantee that such a state
999   change will be observable, since the target resource might be acted
1000   upon by other user agents in parallel, or might be subject to dynamic
1001   processing by the origin server, before any subsequent GET is received.
1002   A successful response only implies that the user agent's intent was
1003   achieved at the time of its processing by the origin server.
[1158]1006   If the target resource does not have a current representation and
1007   the PUT successfully creates one, then the origin server &MUST; inform
1008   the user agent by sending a 201 (Created) response.  If the target
1009   resource does have a current representation and that representation is
1010   successfully modified in accordance with the state of the enclosed
1011   representation, then either a 200 (OK) or 204 (No Content) response
1012   &SHOULD; be sent to indicate successful completion of the request.
1015   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1016   as part of the resource state).
[1158]1019   An origin server &SHOULD; verify that the PUT representation is
1020   consistent with any constraints which the server has for the target
1021   resource that cannot or will not be changed by the PUT.  This is
1022   particularly important when the origin server uses internal
1023   configuration information related to the URI in order to set the
1024   values for representation metadata on GET responses.  When a PUT
1025   representation is inconsistent with the target resource, the origin
1026   server &SHOULD; either make them consistent, by transforming the
1027   representation or changing the resource configuration, or respond
[1168]1028   with an appropriate error message containing sufficient information
1029   to explain why the representation is unsuitable.  The 409 (Conflict)
1030   or 415 (Unsupported Media Type) status codes are suggested, with the
1031   latter being specific to constraints on Content-Type values.
[1158]1034   For example, if the target resource is configured to always have a
1035   Content-Type of "text/html" and the representation being PUT has a
1036   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1037   (a) reconfigure the target resource to reflect the new media type;
1038   (b) transform the PUT representation to a format consistent with that
1039   of the resource before saving it as the new resource state; or,
[1168]1040   (c) reject the request with a 415 response indicating that the target
[1158]1041   resource is limited to "text/html", perhaps including a link to a
1042   different resource that would be a suitable target for the new
1043   representation.
1046   HTTP does not define exactly how a PUT method affects the state
1047   of an origin server beyond what can be expressed by the intent of
1048   the user agent request and the semantics of the origin server response.
1049   It does not define what a resource might be, in any sense of that
1050   word, beyond the interface provided via HTTP.  It does not define
1051   how resource state is "stored", nor how such storage might change
1052   as a result of a change in resource state, nor how the origin server
1053   translates resource state into representations.  Generally speaking,
1054   all implementation details behind the resource interface are
1055   intentionally hidden by the server.
1058   The fundamental difference between the POST and PUT methods is
1059   highlighted by the different intent for the target resource.
1060   The target resource in a POST request is intended to handle the
1061   enclosed representation as a data-accepting process, such as for
1062   a gateway to some other protocol or a document that accepts annotations.
1063   In contrast, the target resource in a PUT request is intended to
1064   take the enclosed representation as a new or replacement value.
1065   Hence, the intent of PUT is idempotent and visible to intermediaries,
1066   even though the exact effect is only known by the origin server.
1069   Proper interpretation of a PUT request presumes that the user agent
1070   knows what target resource is desired.  A service that is intended
1071   to select a proper URI on behalf of the client, after receiving
1072   a state-changing request, &SHOULD; be implemented using the POST
1073   method rather than PUT.  If the origin server will not make the
1074   requested PUT state change to the target resource and instead
1075   wishes to have it applied to a different resource, such as when the
1076   resource has been moved to a different URI, then the origin server
1077   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
[8]1078   then make its own decision regarding whether or not to redirect the
1079   request.
[1158]1082   A PUT request applied to the target resource &MAY; have side-effects
1083   on other resources.  For example, an article might have a URI for
1084   identifying "the current version" (a resource) which is separate
1085   from the URIs identifying each particular version (different
1086   resources that at one point shared the same state as the current version
1087   resource).  A successful PUT request on "the current version" URI might
1088   therefore create a new version resource in addition to changing the
1089   state of the target resource, and might also cause links to be added
1090   between the related resources.
[1158]1093   An origin server &SHOULD; reject any PUT request that contains a
1094   Content-Range header field, since it might be misinterpreted as
1095   partial content (or might be partial content that is being mistakenly
1096   PUT as a full representation).  Partial content updates are
1097   possible by targeting a separately identified resource with state
1098   that overlaps a portion of the larger resource, or by using a
1099   different method that has been specifically defined for partial
1100   updates (for example, the PATCH method defined in
1101   <xref target="RFC5789"/>).
[1158]1104   Responses to the PUT method are not cacheable. If a PUT request passes
1105   through a cache that has one or more stored responses for the effective
1106   request URI, those stored responses will be invalidated (see
1107   &p6-invalid;).
1111<section title="DELETE" anchor="DELETE">
1112  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1113  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
[972]1115   The DELETE method requests that the origin server delete the target
1116   resource. This method &MAY; be overridden by
[823]1117   human intervention (or other means) on the origin server. The client cannot
[8]1118   be guaranteed that the operation has been carried out, even if the
1119   status code returned from the origin server indicates that the action
1120   has been completed successfully. However, the server &SHOULD-NOT;
1121   indicate success unless, at the time the response is given, it
1122   intends to delete the resource or move it to an inaccessible
1123   location.
1126   A successful response &SHOULD; be 200 (OK) if the response includes an
[874]1127   representation describing the status, 202 (Accepted) if the action has not
[8]1128   yet been enacted, or 204 (No Content) if the action has been enacted
[866]1129   but the response does not include a representation.
1132   Bodies on DELETE requests have no defined semantics. Note that sending a body
1133   on a DELETE request might cause some existing implementations to reject the
1134   request.
[1111]1137   Responses to the DELETE method are not cacheable. If a DELETE request
1138   passes through a cache that has one or more stored responses for the
1139   effective request URI, those stored responses will be invalidated (see
1140   &p6-invalid;).
1144<section title="TRACE" anchor="TRACE">
[286]1145  <rdf:Description>
1146    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1147  </rdf:Description>
[8]1148  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1149  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
[1161]1151   The TRACE method requests a remote, application-layer loop-back
[8]1152   of the request message. The final recipient of the request
1153   &SHOULD; reflect the message received back to the client as the
[874]1154   message-body of a 200 (OK) response. The final recipient is either the
[1173]1155   origin server or the first proxy to receive a Max-Forwards
[866]1156   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1157   A TRACE request &MUST-NOT; include a message-body.
1160   TRACE allows the client to see what is being received at the other
1161   end of the request chain and use that data for testing or diagnostic
[29]1162   information. The value of the Via header field (&header-via;) is of
[8]1163   particular interest, since it acts as a trace of the request chain.
1164   Use of the Max-Forwards header field allows the client to limit the
1165   length of the request chain, which is useful for testing a chain of
1166   proxies forwarding messages in an infinite loop.
[874]1169   If the request is valid, the response &SHOULD; have a Content-Type of
1170   "message/http" (see &media-type-message-http;) and contain a message-body
1171   that encloses a copy of the entire request message.
[888]1172   Responses to the TRACE method are not cacheable.
1176<section title="CONNECT" anchor="CONNECT">
1177  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1178  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
[1161]1180   The CONNECT method requests that the proxy establish a tunnel
1181   to the request-target and then restrict its behavior to blind
1182   forwarding of packets until the connection is closed.
[1161]1185   When using CONNECT, the request-target &MUST; use the authority form
1186   (&request-target;); i.e., the request-target consists of only the
1187   host name and port number of the tunnel destination, separated by a colon.
1188   For example,
[1064]1190<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
[1101]1196   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
[1061]1197   except end-to-end protocol Upgrade requests, since the
1198   tunnel must be established first.
1201   For example, proxy authentication might be used to establish the
1202   authority to create a tunnel:
[1064]1204<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1207Proxy-Authorization: basic aGVsbG86d29ybGQ=
1211   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1212   on a CONNECT request might cause some existing implementations to reject the
1213   request.
1216   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1217   sent immediately after the blank line. The usual caveats also apply:
1218   data may be discarded if the eventual response is negative, and the
1219   connection may be reset with no response if more than one TCP segment
1220   is outstanding.
1223<section title="Establishing a Tunnel with CONNECT">
1225   Any successful (2xx) response to a CONNECT request indicates that the
1226   proxy has established a connection to the requested host and port,
1227   and has switched to tunneling the current connection to that server
1228   connection.
1231   It may be the case that the proxy itself can only reach the requested
1232   origin server through another proxy.  In this case, the first proxy
1233   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1234   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1235   unless it has either a direct or tunnel connection established to the
1236   authority.
1239   An origin server which receives a CONNECT request for itself &MAY;
1240   respond with a 2xx status code to indicate that a connection is
1241   established.
1244   If at any point either one of the peers gets disconnected, any
1245   outstanding data that came from that peer will be passed to the other
1246   one, and after that also the other connection will be terminated by
1247   the proxy. If there is outstanding data to that peer undelivered,
1248   that data will be discarded.
1256<section title="Status Code Definitions" anchor="">
[867]1258   Each Status-Code is described below, including any metadata required
[579]1259   in the response.
1262<section title="Informational 1xx" anchor="status.1xx">
1264   This class of status code indicates a provisional response,
[994]1265   consisting only of the Status-Line and optional header fields, and is
1266   terminated by an empty line. There are no required header fields for this
[8]1267   class of status code. Since HTTP/1.0 did not define any 1xx status
1268   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1269   except under experimental conditions.
1272   A client &MUST; be prepared to accept one or more 1xx status responses
1273   prior to a regular response, even if the client does not expect a 100
1274   (Continue) status message. Unexpected 1xx status responses &MAY; be
1275   ignored by a user agent.
1278   Proxies &MUST; forward 1xx responses, unless the connection between the
1279   proxy and its client has been closed, or unless the proxy itself
1280   requested the generation of the 1xx response. (For example, if a
1281   proxy adds a "Expect: 100-continue" field when it forwards a request,
1282   then it need not forward the corresponding 100 (Continue)
1283   response(s).)
1286<section title="100 Continue" anchor="status.100">
1287  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1288  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1290   The client &SHOULD; continue with its request. This interim response is
1291   used to inform the client that the initial part of the request has
1292   been received and has not yet been rejected by the server. The client
1293   &SHOULD; continue by sending the remainder of the request or, if the
1294   request has already been completed, ignore this response. The server
1295   &MUST; send a final response after the request has been completed. See
[29]1296   &use100; for detailed discussion of the use and handling of this
[8]1297   status code.
1301<section title="101 Switching Protocols" anchor="status.101">
1302  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1303  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1305   The server understands and is willing to comply with the client's
[29]1306   request, via the Upgrade message header field (&header-upgrade;), for a
[8]1307   change in the application protocol being used on this connection. The
1308   server will switch protocols to those defined by the response's
1309   Upgrade header field immediately after the empty line which
1310   terminates the 101 response.
1313   The protocol &SHOULD; be switched only when it is advantageous to do
1314   so. For example, switching to a newer version of HTTP is advantageous
1315   over older versions, and switching to a real-time, synchronous
1316   protocol might be advantageous when delivering resources that use
1317   such features.
1322<section title="Successful 2xx" anchor="status.2xx">
1324   This class of status code indicates that the client's request was
1325   successfully received, understood, and accepted.
1328<section title="200 OK" anchor="status.200">
1329  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1330  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
[965]1332   The request has succeeded. The payload returned with the response
[8]1333   is dependent on the method used in the request, for example:
1334  <list style="hanging">
1335    <t hangText="GET">
[972]1336          a representation of the target resource is sent in the response;
[8]1337    </t>
1338    <t hangText="HEAD">
[965]1339          the same representation as GET, except without the message-body;
[8]1340    </t>
1341    <t hangText="POST">
[874]1342      a representation describing or containing the result of the action;
[8]1343    </t>
1344    <t hangText="TRACE">
[874]1345      a representation containing the request message as received by the
[8]1346      end server.
1347    </t>
1348  </list>
[886]1351   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1352   freshness for 200 responses.
1356<section title="201 Created" anchor="status.201">
1357  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1358  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
[758]1360   The request has been fulfilled and has resulted in a new resource being
[8]1361   created. The newly created resource can be referenced by the URI(s)
[856]1362   returned in the payload of the response, with the most specific URI
[8]1363   for the resource given by a Location header field. The response
[856]1364   &SHOULD; include a payload containing a list of resource
[8]1365   characteristics and location(s) from which the user or user agent can
[856]1366   choose the one most appropriate. The payload format is specified by
[8]1367   the media type given in the Content-Type header field. The origin
1368   server &MUST; create the resource before returning the 201 status code.
1369   If the action cannot be carried out immediately, the server &SHOULD;
1370   respond with 202 (Accepted) response instead.
1373   A 201 response &MAY; contain an ETag response header field indicating
[874]1374   the current value of the entity-tag for the representation of the resource
[856]1375   just created (see &header-etag;).
1379<section title="202 Accepted" anchor="status.202">
1380  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1381  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1383   The request has been accepted for processing, but the processing has
1384   not been completed.  The request might or might not eventually be
1385   acted upon, as it might be disallowed when processing actually takes
1386   place. There is no facility for re-sending a status code from an
1387   asynchronous operation such as this.
1390   The 202 response is intentionally non-committal. Its purpose is to
1391   allow a server to accept a request for some other process (perhaps a
1392   batch-oriented process that is only run once per day) without
1393   requiring that the user agent's connection to the server persist
[866]1394   until the process is completed. The representation returned with this
[8]1395   response &SHOULD; include an indication of the request's current status
1396   and either a pointer to a status monitor or some estimate of when the
1397   user can expect the request to be fulfilled.
1401<section title="203 Non-Authoritative Information" anchor="status.203">
1402  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1403  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
[965]1405   The returned metadata in the header fields is not the
[8]1406   definitive set as available from the origin server, but is gathered
1407   from a local or a third-party copy. The set presented &MAY; be a subset
1408   or superset of the original version. For example, including local
1409   annotation information about the resource might result in a superset
[867]1410   of the metadata known by the origin server. Use of this
[8]1411   response code is not required and is only appropriate when the
1412   response would otherwise be 200 (OK).
[886]1415   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1416   freshness for 203 responses.
1421<section title="204 No Content" anchor="status.204">
1422  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1423  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
[1257]1425   The 204 (No Content) status code indicates that the server has
1426   successfully fulfilled the request and that there is no additional
1427   content to return in the response payload body.  Metadata in the
1428   response header fields refer to the target resource and its current
1429   representation after the requested action.
[924]1432   For example, if a 204 status code is received in response to a PUT
[1257]1433   request and the response contains an ETag header field, then the PUT
1434   was successful and the ETag field-value contains the entity-tag for
1435   the new representation of that target resource.
[1257]1438   The 204 response allows a server to indicate that the action has been
1439   successfully applied to the target resource while implying that the
1440   user agent &SHOULD-NOT; traverse away from its current "document view"
1441   (if any).  The server assumes that the user agent will provide some
1442   indication of the success to its user, in accord with its own interface,
1443   and apply any new or updated metadata in the response to the active
1444   representation.
1445   For example, a 204 status code is commonly used with document editing
1446   interfaces corresponding to a "save" action, such that the document
1447   being saved remains available to the user for editing. It is also
1448   frequently used with interfaces that expect automated data transfers
1449   to be prevalent, such as within distributed version control systems.
1452   The 204 response &MUST-NOT; include a message-body, and thus is always
1453   terminated by the first empty line after the header fields.
1457<section title="205 Reset Content" anchor="status.205">
1458  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1459  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1461   The server has fulfilled the request and the user agent &SHOULD; reset
1462   the document view which caused the request to be sent. This response
1463   is primarily intended to allow input for actions to take place via
1464   user input, followed by a clearing of the form in which the input is
[1058]1465   given so that the user can easily initiate another input action.
1468   The message-body included with the response &MUST; be empty. Note that
1469   receivers still need to parse the response according to the algorithm defined
1470   in &message-body;.
1474<section title="206 Partial Content" anchor="status.206">
1475  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1476  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
[700]1477  <rdf:Description>
1478    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1479  </rdf:Description>
[29]1481   The server has fulfilled the partial GET request for the resource
[874]1482   and the enclosed payload is a partial representation as defined in &status-206;.
[886]1485   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1486   freshness for 206 responses.
1491<section title="Redirection 3xx" anchor="status.3xx">
1493   This class of status code indicates that further action needs to be
1494   taken by the user agent in order to fulfill the request.  The action
1495   required &MAY; be carried out by the user agent without interaction
1496   with the user if and only if the method used in the second request is
[760]1497   known to be "safe", as defined in <xref target="safe.methods"/>.
[759]1498   A client &SHOULD; detect infinite redirection loops, since such loops
1499   generate network traffic for each redirection.
1502  <t>
[756]1503    <x:h>Note:</x:h> An earlier version of this specification recommended a
[629]1504    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
[969]1505    Content developers need to be aware that some clients might
[629]1506    implement such a fixed limitation.
[563]1507  </t>
1510<section title="300 Multiple Choices" anchor="status.300">
1511  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1512  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
[1029]1514   The target resource has more than one
[965]1515   representation, each with its own specific location, and agent-driven
[29]1516   negotiation information (&content-negotiation;) is being provided so that
[965]1517   the user (or user agent) can select a preferred representation by
1518   redirecting its request to that location.
[866]1521   Unless it was a HEAD request, the response &SHOULD; include a representation
[965]1522   containing a list of representation metadata and location(s) from
[8]1523   which the user or user agent can choose the one most appropriate. The
[866]1524   data format is specified by the media type given in the Content-Type
[8]1525   header field. Depending upon the format and the capabilities of
1526   the user agent, selection of the most appropriate choice &MAY; be
1527   performed automatically. However, this specification does not define
1528   any standard for such automatic selection.
1531   If the server has a preferred choice of representation, it &SHOULD;
1532   include the specific URI for that representation in the Location
1533   field; user agents &MAY; use the Location field value for automatic
[884]1534   redirection.
[886]1537   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1538   freshness for 300 responses.
1543<section title="301 Moved Permanently" anchor="status.301">
1544  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1545  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
[965]1547   The target resource has been assigned a new permanent URI and any
[8]1548   future references to this resource &SHOULD; use one of the returned
1549   URIs.  Clients with link editing capabilities ought to automatically
[965]1550   re-link references to the effective request URI to one or more of the new
[884]1551   references returned by the server, where possible.
[886]1554   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1555   freshness for 301 responses.
[8]1558   The new permanent URI &SHOULD; be given by the Location field in the
[866]1559   response. Unless the request method was HEAD, the representation of the
[8]1560   response &SHOULD; contain a short hypertext note with a hyperlink to
1561   the new URI(s).
[88]1564   If the 301 status code is received in response to a request method
1565   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1566   then the request &MAY; be automatically redirected by the user agent without
[88]1567   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1568   request unless it can be confirmed by the user, since this might
1569   change the conditions under which the request was issued.
1572  <t>
1573    <x:h>Note:</x:h> When automatically redirecting a POST request after
1574    receiving a 301 status code, some existing HTTP/1.0 user agents
1575    will erroneously change it into a GET request.
1576  </t>
1580<section title="302 Found" anchor="status.302">
1581  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1582  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
[965]1584   The target resource resides temporarily under a different URI.
[8]1585   Since the redirection might be altered on occasion, the client &SHOULD;
[965]1586   continue to use the effective request URI for future requests.
1589   The temporary URI &SHOULD; be given by the Location field in the
[866]1590   response. Unless the request method was HEAD, the representation of the
[8]1591   response &SHOULD; contain a short hypertext note with a hyperlink to
1592   the new URI(s).
[88]1595   If the 302 status code is received in response to a request method
1596   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1597   then the request &MAY; be automatically redirected by the user agent without
[88]1598   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1599   request unless it can be confirmed by the user, since this might
1600   change the conditions under which the request was issued.
1603  <t>
[614]1604    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1605    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1606    specify that the client is not allowed to change the method on the
1607    redirected request.  However, most existing user agent implementations
1608    treat 302 as if it were a 303 response, performing a GET on the Location
1609    field-value regardless of the original request method. Therefore, a
1610    previous version of this specification
1611    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1612    status codes
1613    <xref target="status.303" format="none">303</xref> and
1614    <xref target="status.307" format="none">307</xref> for servers that wish
1615    to make unambiguously clear which kind of reaction is expected of the
1616    client.
[563]1617  </t>
1621<section title="303 See Other" anchor="status.303">
1622  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1623  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
[242]1625   The server directs the user agent to a different resource, indicated
1626   by a URI in the Location header field, that provides an indirect
1627   response to the original request.  The user agent &MAY; perform a GET
1628   request on the URI in the Location field in order to obtain a
1629   representation corresponding to the response, be redirected again,
1630   or end with an error status.  The Location URI is not a substitute
[965]1631   reference for the effective request URI.
[924]1634   The 303 status code is generally applicable to any HTTP method.  It is
[242]1635   primarily used to allow the output of a POST action to redirect
1636   the user agent to a selected resource, since doing so provides the
1637   information corresponding to the POST response in a form that
1638   can be separately identified, bookmarked, and cached independent
1639   of the original request.
1642   A 303 response to a GET request indicates that the requested
1643   resource does not have a representation of its own that can be
1644   transferred by the server over HTTP.  The Location URI indicates a
[965]1645   resource that is descriptive of the target resource, such that the
1646   follow-on representation might be useful to recipients without
1647   implying that it adequately represents the target resource.
[242]1648   Note that answers to the questions of what can be represented, what
1649   representations are adequate, and what might be a useful description
1650   are outside the scope of HTTP and thus entirely determined by the
[602]1651   URI owner(s).
[884]1654   Except for responses to a HEAD request, the representation of a 303
1655   response &SHOULD; contain a short hypertext note with a hyperlink
1656   to the Location URI.
1660<section title="304 Not Modified" anchor="status.304">
1661  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1662  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
[700]1663  <rdf:Description>
1664    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1665  </rdf:Description>
[45]1667   The response to the request has not been modified since the conditions
[700]1668   indicated by the client's conditional GET request, as defined in &status-304;.
1672<section title="305 Use Proxy" anchor="status.305">
1673  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1674  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
[924]1676   The 305 status code was defined in a previous version of this specification
[235]1677   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1681<section title="306 (Unused)" anchor="status.306">
1682  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1683  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1685   The 306 status code was used in a previous version of the
1686   specification, is no longer used, and the code is reserved.
1690<section title="307 Temporary Redirect" anchor="status.307">
1691  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1692  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
[965]1694   The target resource resides temporarily under a different URI.
[954]1695   Since the redirection can change over time, the client &SHOULD;
[965]1696   continue to use the effective request URI for future requests.
1699   The temporary URI &SHOULD; be given by the Location field in the
[866]1700   response. Unless the request method was HEAD, the representation of the
[8]1701   response &SHOULD; contain a short hypertext note with a hyperlink to
[1030]1702   the new URI(s), since many pre-HTTP/1.1 user agents do not
[924]1703   understand the 307 status code. Therefore, the note &SHOULD; contain the
[8]1704   information necessary for a user to repeat the original request on
1705   the new URI.
[88]1708   If the 307 status code is received in response to a request method
1709   that is known to be "safe", as defined in <xref target="safe.methods"/>,
[96]1710   then the request &MAY; be automatically redirected by the user agent without
[88]1711   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
[8]1712   request unless it can be confirmed by the user, since this might
1713   change the conditions under which the request was issued.
1718<section title="Client Error 4xx" anchor="status.4xx">
1720   The 4xx class of status code is intended for cases in which the
1721   client seems to have erred. Except when responding to a HEAD request,
[874]1722   the server &SHOULD; include a representation containing an explanation of the
[8]1723   error situation, and whether it is a temporary or permanent
1724   condition. These status codes are applicable to any request method.
[874]1725   User agents &SHOULD; display any included representation to the user.
1728   If the client is sending data, a server implementation using TCP
1729   &SHOULD; be careful to ensure that the client acknowledges receipt of
1730   the packet(s) containing the response, before the server closes the
1731   input connection. If the client continues sending data to the server
1732   after the close, the server's TCP stack will send a reset packet to
[901]1733   the client, which might erase the client's unacknowledged input buffers
[8]1734   before they can be read and interpreted by the HTTP application.
1737<section title="400 Bad Request" anchor="status.400">
1738  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1739  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1741   The request could not be understood by the server due to malformed
[885]1742   syntax. The client &SHOULD-NOT; repeat the request without
[8]1743   modifications.
1747<section title="401 Unauthorized" anchor="status.401">
1748  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1749  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
[700]1750  <rdf:Description>
1751    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1752  </rdf:Description>
[700]1754   The request requires user authentication (see &status-401;).
1758<section title="402 Payment Required" anchor="status.402">
1759  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1760  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1762   This code is reserved for future use.
1766<section title="403 Forbidden" anchor="status.403">
1767  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1768  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1770   The server understood the request, but is refusing to fulfill it.
1771   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1772   If the request method was not HEAD and the server wishes to make
1773   public why the request has not been fulfilled, it &SHOULD; describe the
[866]1774   reason for the refusal in the representation.  If the server does not wish to
[8]1775   make this information available to the client, the status code 404
1776   (Not Found) can be used instead.
1780<section title="404 Not Found" anchor="status.404">
1781  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1782  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
[965]1784   The server has not found anything matching the effective request URI. No
[8]1785   indication is given of whether the condition is temporary or
1786   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1787   knows, through some internally configurable mechanism, that an old
1788   resource is permanently unavailable and has no forwarding address.
1789   This status code is commonly used when the server does not wish to
1790   reveal exactly why the request has been refused, or when no other
1791   response is applicable.
1795<section title="405 Method Not Allowed" anchor="status.405">
1796  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1797  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
[965]1799   The method specified in the Request-Line is not allowed for the target
1800   resource. The response &MUST; include an
[994]1801   Allow header field containing a list of valid methods for the requested
[8]1802   resource.
1806<section title="406 Not Acceptable" anchor="status.406">
1807  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1808  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1810   The resource identified by the request is only capable of generating
[874]1811   response representations which have content characteristics not acceptable
[994]1812   according to the accept header fields sent in the request.
[866]1815   Unless it was a HEAD request, the response &SHOULD; include a representation
1816   containing a list of available representation characteristics and location(s)
[8]1817   from which the user or user agent can choose the one most
[866]1818   appropriate. The data format is specified by the media type given
[8]1819   in the Content-Type header field. Depending upon the format and the
1820   capabilities of the user agent, selection of the most appropriate
1821   choice &MAY; be performed automatically. However, this specification
1822   does not define any standard for such automatic selection.
1825  <t>
1826    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
[994]1827    not acceptable according to the accept header fields sent in the
[901]1828    request. In some cases, this might even be preferable to sending a
[994]1829    406 response. User agents are encouraged to inspect the header fields of
[563]1830    an incoming response to determine if it is acceptable.
1831  </t>
1834   If the response could be unacceptable, a user agent &SHOULD;
1835   temporarily stop receipt of more data and query the user for a
1836   decision on further actions.
1840<section title="407 Proxy Authentication Required" anchor="status.407">
1841  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1842  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1844   This code is similar to 401 (Unauthorized), but indicates that the
[700]1845   client must first authenticate itself with the proxy (see &status-407;).
1849<section title="408 Request Timeout" anchor="status.408">
1850  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1851  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1853   The client did not produce a request within the time that the server
1854   was prepared to wait. The client &MAY; repeat the request without
1855   modifications at any later time.
1859<section title="409 Conflict" anchor="status.409">
1860  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1861  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1863   The request could not be completed due to a conflict with the current
1864   state of the resource. This code is only allowed in situations where
1865   it is expected that the user might be able to resolve the conflict
1866   and resubmit the request. The response body &SHOULD; include enough
1867   information for the user to recognize the source of the conflict.
[874]1868   Ideally, the response representation would include enough information for the
[8]1869   user or user agent to fix the problem; however, that might not be
1870   possible and is not required.
1873   Conflicts are most likely to occur in response to a PUT request. For
[866]1874   example, if versioning were being used and the representation being PUT
[8]1875   included changes to a resource which conflict with those made by an
1876   earlier (third-party) request, the server might use the 409 response
1877   to indicate that it can't complete the request. In this case, the
[866]1878   response representation would likely contain a list of the differences
[8]1879   between the two versions in a format defined by the response
1880   Content-Type.
1884<section title="410 Gone" anchor="status.410">
1885  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1886  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
[965]1888   The target resource is no longer available at the server and no
[8]1889   forwarding address is known. This condition is expected to be
1890   considered permanent. Clients with link editing capabilities &SHOULD;
[965]1891   delete references to the effective request URI after user approval. If the
[8]1892   server does not know, or has no facility to determine, whether or not
1893   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
[884]1894   used instead.
1897   The 410 response is primarily intended to assist the task of web
1898   maintenance by notifying the recipient that the resource is
1899   intentionally unavailable and that the server owners desire that
1900   remote links to that resource be removed. Such an event is common for
1901   limited-time, promotional services and for resources belonging to
1902   individuals no longer working at the server's site. It is not
1903   necessary to mark all permanently unavailable resources as "gone" or
[1101]1904   to keep the mark for any length of time &mdash; that is left to the
[8]1905   discretion of the server owner.
[886]1908   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1909   for 410 responses.
1914<section title="411 Length Required" anchor="status.411">
1915  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1916  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1918   The server refuses to accept the request without a defined Content-Length.
1919   The client &MAY; repeat the request if it adds a valid
1920   Content-Length header field containing the length of the message-body
1921   in the request message.
1925<section title="412 Precondition Failed" anchor="status.412">
1926  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1927  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
[700]1928  <rdf:Description>
1929    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1930  </rdf:Description>
[1163]1932   The precondition given in one or more of the header fields
[45]1933   evaluated to false when it was tested on the server, as defined in
[700]1934   &status-412;.
1938<section title="413 Request Entity Too Large" anchor="status.413">
1939  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1940  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1942   The server is refusing to process a request because the request
[874]1943   representation is larger than the server is willing or able to process. The
[8]1944   server &MAY; close the connection to prevent the client from continuing
1945   the request.
1948   If the condition is temporary, the server &SHOULD; include a Retry-After
1949   header field to indicate that it is temporary and after what
1950   time the client &MAY; try again.
[465]1954<section title="414 URI Too Long" anchor="status.414">
1955  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1956  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
[965]1958   The server is refusing to service the request because the effective request URI
[8]1959   is longer than the server is willing to interpret. This rare
1960   condition is only likely to occur when a client has improperly
1961   converted a POST request to a GET request with long query
1962   information, when the client has descended into a URI "black hole" of
1963   redirection (e.g., a redirected URI prefix that points to a suffix of
1964   itself), or when the server is under attack by a client attempting to
1965   exploit security holes present in some servers using fixed-length
[965]1966   buffers for reading or manipulating the effective request URI.
1970<section title="415 Unsupported Media Type" anchor="status.415">
1971  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1972  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
[1161]1974   The server is refusing to service the request because the request
1975   payload is in a format not supported by this request method on the
1976   target resource.
1980<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1981  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1982  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
[700]1983  <rdf:Description>
1984    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1985  </rdf:Description>
[1163]1987   The request included a Range header field (&header-range;) and none of
[8]1988   the range-specifier values in this field overlap the current extent
[885]1989   of the selected resource. See &status-416;.
1993<section title="417 Expectation Failed" anchor="status.417">
1994  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1995  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
[1163]1997   The expectation given in an Expect header field (see <xref target="header.expect"/>)
[8]1998   could not be met by this server, or, if the server is a proxy,
1999   the server has unambiguous evidence that the request could not be met
2000   by the next-hop server.
2004<section title="426 Upgrade Required" anchor="status.426">
2005  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2006  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2008   The request can not be completed without a prior protocol upgrade. This
2009   response &MUST; include an Upgrade header field (&header-upgrade;)
2010   specifying the required protocols.
2014<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2015HTTP/1.1 426 Upgrade Required
2016Upgrade: HTTP/2.0
2017Connection: Upgrade
2021   The server &SHOULD; include a message body in the 426 response which
2022   indicates in human readable form the reason for the error and describes any
2023   alternative courses which may be available to the user.
2028<section title="Server Error 5xx" anchor="status.5xx">
2030   Response status codes beginning with the digit "5" indicate cases in
2031   which the server is aware that it has erred or is incapable of
2032   performing the request. Except when responding to a HEAD request, the
[874]2033   server &SHOULD; include a representation containing an explanation of the
[8]2034   error situation, and whether it is a temporary or permanent
[874]2035   condition. User agents &SHOULD; display any included representation to the
[8]2036   user. These response codes are applicable to any request method.
2039<section title="500 Internal Server Error" anchor="status.500">
2040  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2041  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2043   The server encountered an unexpected condition which prevented it
2044   from fulfilling the request.
2048<section title="501 Not Implemented" anchor="status.501">
2049  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2050  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2052   The server does not support the functionality required to fulfill the
2053   request. This is the appropriate response when the server does not
2054   recognize the request method and is not capable of supporting it for
2055   any resource.
2059<section title="502 Bad Gateway" anchor="status.502">
2060  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2061  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2063   The server, while acting as a gateway or proxy, received an invalid
2064   response from the upstream server it accessed in attempting to
2065   fulfill the request.
2069<section title="503 Service Unavailable" anchor="status.503">
2070  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2071  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2073   The server is currently unable to handle the request due to a
2074   temporary overloading or maintenance of the server. The implication
2075   is that this is a temporary condition which will be alleviated after
2076   some delay. If known, the length of the delay &MAY; be indicated in a
[994]2077   Retry-After header field. If no Retry-After is given, the client &SHOULD;
[8]2078   handle the response as it would for a 500 response.
2081  <t>
2082    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
[901]2083    server must use it when becoming overloaded. Some servers might wish
[563]2084    to simply refuse the connection.
2085  </t>
2089<section title="504 Gateway Timeout" anchor="status.504">
2090  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2091  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2093   The server, while acting as a gateway or proxy, did not receive a
[763]2094   timely response from the upstream server specified by the URI (e.g.,
2095   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
[8]2096   to access in attempting to complete the request.
2099  <t>
[757]2100    <x:h>Note</x:h> to implementors: some deployed proxies are known to
[563]2101    return 400 or 500 when DNS lookups time out.
2102  </t>
2106<section title="505 HTTP Version Not Supported" anchor="status.505">
2107  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2108  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
[172]2110   The server does not support, or refuses to support, the protocol
[8]2111   version that was used in the request message. The server is
2112   indicating that it is unable or unwilling to complete the request
[29]2113   using the same major version as the client, as described in &http-version;,
[8]2114   other than with this error message. The response &SHOULD; contain
[874]2115   a representation describing why that version is not supported and what other
[8]2116   protocols are supported by that server.
2124<section title="Header Field Definitions" anchor="header.fields">
[117]2126   This section defines the syntax and semantics of HTTP/1.1 header fields
2127   related to request and response semantics.
2130<section title="Allow" anchor="header.allow">
[1120]2131  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2132  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
[229]2133  <x:anchor-alias value="Allow"/>
[1163]2135   The "Allow" header field lists the set of methods advertised as
[1067]2136   supported by the target resource. The purpose of this field is strictly to
[1161]2137   inform the recipient of valid request methods associated with the resource.
[1235]2139<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2140  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
[1067]2143   Example of use:
2145<figure><artwork type="example">
[356]2146  Allow: GET, HEAD, PUT
[1067]2149   The actual set of allowed methods is defined by the origin server at the
2150   time of each request.
[1101]2153   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
[1068]2154   understand all the methods specified in order to handle them according to
2155   the generic message handling rules.
2159<section title="Expect" anchor="header.expect">
[1120]2160  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2161  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
[229]2162  <x:anchor-alias value="Expect"/>
2163  <x:anchor-alias value="expectation"/>
2164  <x:anchor-alias value="expectation-extension"/>
2165  <x:anchor-alias value="expect-params"/>
[1163]2167   The "Expect" header field is used to indicate that particular
[8]2168   server behaviors are required by the client.
[1235]2170<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
2171  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
[356]2173  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2174  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
[229]2175                           *<x:ref>expect-params</x:ref> ]
[356]2176  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2179   A server that does not understand or is unable to comply with any of
2180   the expectation values in the Expect field of a request &MUST; respond
[924]2181   with appropriate error status code. The server &MUST; respond with a 417
2182   (Expectation Failed) status code if any of the expectations cannot be met
[8]2183   or, if there are other problems with the request, some other 4xx
[924]2184   status code.
2187   This header field is defined with extensible syntax to allow for
2188   future extensions. If a server receives a request containing an
2189   Expect field that includes an expectation-extension that it does not
[924]2190   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2193   Comparison of expectation values is case-insensitive for unquoted
2194   tokens (including the 100-continue token), and is case-sensitive for
2195   quoted-string expectation-extensions.
2198   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
[924]2199   return a 417 (Expectation Failed) status code if it receives a request
[8]2200   with an expectation that it cannot meet. However, the Expect
[1163]2201   header field itself is end-to-end; it &MUST; be forwarded if the
[8]2202   request is forwarded.
2205   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
[994]2206   Expect header field.
[924]2209   See &use100; for the use of the 100 (Continue) status code.
2213<section title="From" anchor="header.from">
[1120]2214  <iref primary="true" item="From header field" x:for-anchor=""/>
2215  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
[229]2216  <x:anchor-alias value="From"/>
2217  <x:anchor-alias value="mailbox"/>
[1163]2219   The "From" header field, if given, &SHOULD; contain an Internet
[8]2220   e-mail address for the human user who controls the requesting user
2221   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
[327]2222   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
[1235]2224<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2225  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
[327]2227  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2230   An example is:
2232<figure><artwork type="example">
[356]2233  From:
2236   This header field &MAY; be used for logging purposes and as a means for
2237   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
2238   be used as an insecure form of access protection. The interpretation
2239   of this field is that the request is being performed on behalf of the
2240   person given, who accepts responsibility for the method performed. In
[994]2241   particular, robot agents &SHOULD; include this header field so that the
[8]2242   person responsible for running the robot can be contacted if problems
2243   occur on the receiving end.
2246   The Internet e-mail address in this field &MAY; be separate from the
2247   Internet host which issued the request. For example, when a request
2248   is passed through a proxy the original issuer's address &SHOULD; be
2249   used.
2252   The client &SHOULD-NOT;  send the From header field without the user's
2253   approval, as it might conflict with the user's privacy interests or
2254   their site's security policy. It is strongly recommended that the
2255   user be able to disable, enable, and modify the value of this field
2256   at any time prior to a request.
2260<section title="Location" anchor="header.location">
[1120]2261  <iref primary="true" item="Location header field" x:for-anchor=""/>
2262  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
[229]2263  <x:anchor-alias value="Location"/>
[1163]2265   The "Location" header field is used to identify a newly created
[698]2266   resource, or to redirect the recipient to a different location for
2267   completion of the request.
2270   For 201 (Created) responses, the Location is the URI of the new resource
2271   which was created by the request. For 3xx responses, the location &SHOULD;
2272   indicate the server's preferred URI for automatic redirection to the
2273   resource.
[785]2276   The field value consists of a single URI-reference. When it has the form
2277   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2278   the final value is computed by resolving it against the effective request
2279   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
[1235]2281<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2282  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2285<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2286<artwork type="example">
2287  Location:
2288</artwork></figure><figure><artwork type="example">  Location: /index.html
[785]2291   There are circumstances in which a fragment identifier in a Location URI
2292   would not be appropriate:
[659]2293   <list style="symbols">
[785]2294      <t>With a 201 Created response, because in this usage the Location header
[994]2295      field specifies the URI for the entire created resource.</t>
[659]2296      <t>With 305 Use Proxy.</t>
2297   </list>
2300  <t>
[785]2301    <x:h>Note:</x:h> This specification does not define precedence rules
[791]2302    for the case where the original URI, as navigated to by the user
[785]2303    agent, and the Location header field value both contain fragment
[1097]2304    identifiers. Thus be aware that including fragment identifiers might
2305    inconvenience anyone relying on the semantics of the original URI's
2306    fragment identifier.
[785]2307  </t>
2310  <t>
[563]2311    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
[866]2312    from Location in that the Content-Location identifies the most specific
2313    resource corresponding to the enclosed representation.
2314    It is therefore possible for a response to contain header fields for
2315    both Location and Content-Location.
[563]2316  </t>
2320<section title="Max-Forwards" anchor="header.max-forwards">
[1120]2321  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2322  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
[229]2323  <x:anchor-alias value="Max-Forwards"/>
[1163]2325   The "Max-Forwards" header field provides a mechanism with the
[698]2326   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2327   methods to limit the number of times that the request is forwarded by
[1173]2328   proxies. This can be useful when the client is attempting to
[698]2329   trace a request which appears to be failing or looping in mid-chain.
[1235]2331<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2332  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2335   The Max-Forwards value is a decimal integer indicating the remaining
[901]2336   number of times this request message can be forwarded.
[1173]2339   Each recipient of a TRACE or OPTIONS request
[8]2340   containing a Max-Forwards header field &MUST; check and update its
2341   value prior to forwarding the request. If the received value is zero
2342   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2343   respond as the final recipient. If the received Max-Forwards value is
2344   greater than zero, then the forwarded message &MUST; contain an updated
2345   Max-Forwards field with a value decremented by one (1).
[1161]2348   The Max-Forwards header field &MAY; be ignored for all other request
2349   methods.
2353<section title="Referer" anchor="header.referer">
[1120]2354  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2355  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
[229]2356  <x:anchor-alias value="Referer"/>
[1163]2358   The "Referer" [sic] header field allows the client to specify the
[965]2359   URI of the resource from which the effective request URI was obtained (the
[698]2360   "referrer", although the header field is misspelled.).
[994]2363   The Referer header field allows servers to generate lists of back-links to
[593]2364   resources for interest, logging, optimized caching, etc. It also allows
2365   obsolete or mistyped links to be traced for maintenance. Some servers use
2366   Referer as a means of controlling where they allow links from (so-called
[969]2367   "deep linking"), but legitimate requests do not always
2368   contain a Referer header field.
[965]2371   If the effective request URI was obtained from a source that does not have its own
[812]2372   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
[593]2373   sent with the value "about:blank", or not be sent at all. Note that this
2374   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
[1235]2376<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2377  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2380   Example:
2382<figure><artwork type="example">
[356]2383  Referer:
2386   If the field value is a relative URI, it &SHOULD; be interpreted
[965]2387   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
[8]2388   <xref target=""/> for security considerations.
2392<section title="Retry-After" anchor="header.retry-after">
[1120]2393  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2394  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
[229]2395  <x:anchor-alias value="Retry-After"/>
[1163]2397   The header "Retry-After" field can be used with a 503 (Service
[8]2398   Unavailable) response to indicate how long the service is expected to
2399   be unavailable to the requesting client. This field &MAY; also be used
2400   with any 3xx (Redirection) response to indicate the minimum time the
[698]2401   user-agent is asked wait before issuing the redirected request.
2404   The value of this field can be either an HTTP-date or an integer number
[8]2405   of seconds (in decimal) after the time of the response.
[1235]2407<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2408  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
[229]2410<t anchor="">
2411  <x:anchor-alias value="delta-seconds"/>
[212]2412   Time spans are non-negative decimal integers, representing time in
2413   seconds.
2415<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
[229]2416  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
[8]2419   Two examples of its use are
2421<figure><artwork type="example">
[356]2422  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2423  Retry-After: 120
2426   In the latter example, the delay is 2 minutes.
2430<section title="Server" anchor="header.server">
[1120]2431  <iref primary="true" item="Server header field" x:for-anchor=""/>
2432  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
[229]2433  <x:anchor-alias value="Server"/>
[1163]2435   The "Server" header field contains information about the
[698]2436   software used by the origin server to handle the request.
2439   The field can contain multiple product tokens (&product-tokens;) and
2440   comments (&header-fields;) identifying the server and any significant
2441   subproducts. The product tokens are listed in order of their significance
2442   for identifying the application.
[1235]2444<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2445  <x:ref>Server</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2448   Example:
2450<figure><artwork type="example">
[356]2451  Server: CERN/3.0 libwww/2.17
2454   If the response is being forwarded through a proxy, the proxy
[1163]2455   application &MUST-NOT; modify the Server header field. Instead, it
[72]2456   &MUST; include a Via field (as described in &header-via;).
2459  <t>
2460    <x:h>Note:</x:h> Revealing the specific software version of the server might
2461    allow the server machine to become more vulnerable to attacks
2462    against software that is known to contain security holes. Server
2463    implementors are encouraged to make this field a configurable
2464    option.
2465  </t>
2469<section title="User-Agent" anchor="header.user-agent">
[1120]2470  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2471  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
[229]2472  <x:anchor-alias value="User-Agent"/>
[1163]2474   The "User-Agent" header field contains information about the user
[1036]2475   agent originating the request. User agents &SHOULD; include this field with
2476   requests.
2479   Typically, it is used for statistical purposes, the tracing of protocol
2480   violations, and tailoring responses to avoid particular user agent
2481   limitations.
2484   The field can contain multiple product tokens (&product-tokens;)
2485   and comments (&header-fields;) identifying the agent and its
2486   significant subproducts. By convention, the product tokens are listed in
2487   order of their significance for identifying the application.
2490   Because this field is usually sent on every request a user agent makes,
2491   implementations are encouraged not to include needlessly fine-grained
2492   detail, and to limit (or even prohibit) the addition of subproducts by third
2493   parties. Overly long and detailed User-Agent field values make requests
2494   larger and can also be used to identify ("fingerprint") the user against
2495   their wishes.
2498   Likewise, implementations are encouraged not to use the product tokens of
2499   other implementations in order to declare compatibility with them, as this
2500   circumvents the purpose of the field. Finally, they are encouraged not to
2501   use comments to identify products; doing so makes the field value more
2502   difficult to parse.
[1235]2504<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2505  <x:ref>User-Agent</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2508   Example:
2510<figure><artwork type="example">
[356]2511  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
[29]2517<section title="IANA Considerations" anchor="IANA.considerations">
2519<section title="Method Registry" anchor="method.registration">
[1161]2521  The registration procedure for HTTP request methods is defined by
[270]2522  <xref target="method.registry"/> of this document.
[969]2525   The HTTP Method Registry shall be created at <eref target=""/>
[818]2526   and be populated with the registrations below:
[682]2528<?BEGININC p2-semantics.iana-methods ?>
[270]2529<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
[288]2530<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
[270]2531   <ttcol>Method</ttcol>
[286]2532   <ttcol>Safe</ttcol>
[270]2533   <ttcol>Reference</ttcol>
2534   <c>CONNECT</c>
[286]2535   <c>no</c>
[270]2536   <c>
2537      <xref target="CONNECT"/>
2538   </c>
2539   <c>DELETE</c>
[286]2540   <c>no</c>
[270]2541   <c>
2542      <xref target="DELETE"/>
2543   </c>
2544   <c>GET</c>
[286]2545   <c>yes</c>
[270]2546   <c>
2547      <xref target="GET"/>
2548   </c>
2549   <c>HEAD</c>
[286]2550   <c>yes</c>
[270]2551   <c>
2552      <xref target="HEAD"/>
2553   </c>
2554   <c>OPTIONS</c>
[286]2555   <c>yes</c>
[270]2556   <c>
2557      <xref target="OPTIONS"/>
2558   </c>
2559   <c>POST</c>
[286]2560   <c>no</c>
[270]2561   <c>
2562      <xref target="POST"/>
2563   </c>
2564   <c>PUT</c>
[286]2565   <c>no</c>
[270]2566   <c>
2567      <xref target="PUT"/>
2568   </c>
2569   <c>TRACE</c>
[286]2570   <c>yes</c>
[270]2571   <c>
2572      <xref target="TRACE"/>
2573   </c>
[682]2576<?ENDINC p2-semantics.iana-methods ?>
[255]2579<section title="Status Code Registry" anchor="status.code.registration">
[1101]2581   The registration procedure for HTTP Status Codes &mdash; previously defined
2582   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
[288]2583   by <xref target="status.code.registry"/> of this document.
2586   The HTTP Status Code Registry located at <eref target=""/>
[969]2587   shall be updated with the registrations below:
[682]2589<?BEGININC p2-semantics.iana-status-codes ?>
[255]2590<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
[288]2591<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
[255]2592   <ttcol>Value</ttcol>
2593   <ttcol>Description</ttcol>
2594   <ttcol>Reference</ttcol>
2595   <c>100</c>
2596   <c>Continue</c>
2597   <c>
2598      <xref target="status.100"/>
2599   </c>
2600   <c>101</c>
2601   <c>Switching Protocols</c>
2602   <c>
2603      <xref target="status.101"/>
2604   </c>
2605   <c>200</c>
2606   <c>OK</c>
2607   <c>
2608      <xref target="status.200"/>
2609   </c>
2610   <c>201</c>
2611   <c>Created</c>
2612   <c>
2613      <xref target="status.201"/>
2614   </c>
2615   <c>202</c>
2616   <c>Accepted</c>
2617   <c>
2618      <xref target="status.202"/>
2619   </c>
2620   <c>203</c>
2621   <c>Non-Authoritative Information</c>
2622   <c>
2623      <xref target="status.203"/>
2624   </c>
2625   <c>204</c>
2626   <c>No Content</c>
2627   <c>
2628      <xref target="status.204"/>
2629   </c>
2630   <c>205</c>
2631   <c>Reset Content</c>
2632   <c>
2633      <xref target="status.205"/>
2634   </c>
2635   <c>300</c>
2636   <c>Multiple Choices</c>
2637   <c>
2638      <xref target="status.300"/>
2639   </c>
2640   <c>301</c>
2641   <c>Moved Permanently</c>
2642   <c>
2643      <xref target="status.301"/>
2644   </c>
2645   <c>302</c>
2646   <c>Found</c>
2647   <c>
2648      <xref target="status.302"/>
2649   </c>
2650   <c>303</c>
2651   <c>See Other</c>
2652   <c>
2653      <xref target="status.303"/>
2654   </c>
2655   <c>305</c>
2656   <c>Use Proxy</c>
2657   <c>
2658      <xref target="status.305"/>
2659   </c>
2660   <c>306</c>
2661   <c>(Unused)</c>
2662   <c>
2663      <xref target="status.306"/>
2664   </c>
2665   <c>307</c>
2666   <c>Temporary Redirect</c>
2667   <c>
2668      <xref target="status.307"/>
2669   </c>
2670   <c>400</c>
2671   <c>Bad Request</c>
2672   <c>
2673      <xref target="status.400"/>
2674   </c>
2675   <c>402</c>
2676   <c>Payment Required</c>
2677   <c>
2678      <xref target="status.402"/>
2679   </c>
2680   <c>403</c>
2681   <c>Forbidden</c>
2682   <c>
2683      <xref target="status.403"/>
2684   </c>
2685   <c>404</c>
2686   <c>Not Found</c>
2687   <c>
2688      <xref target="status.404"/>
2689   </c>
2690   <c>405</c>
2691   <c>Method Not Allowed</c>
2692   <c>
2693      <xref target="status.405"/>
2694   </c>
2695   <c>406</c>
2696   <c>Not Acceptable</c>
2697   <c>
2698      <xref target="status.406"/>
2699   </c>
2700   <c>407</c>
2701   <c>Proxy Authentication Required</c>
2702   <c>
2703      <xref target="status.407"/>
2704   </c>
2705   <c>408</c>
2706   <c>Request Timeout</c>
2707   <c>
2708      <xref target="status.408"/>
2709   </c>
2710   <c>409</c>
2711   <c>Conflict</c>
2712   <c>
2713      <xref target="status.409"/>
2714   </c>
2715   <c>410</c>
2716   <c>Gone</c>
2717   <c>
2718      <xref target="status.410"/>
2719   </c>
2720   <c>411</c>
2721   <c>Length Required</c>
2722   <c>
2723      <xref target="status.411"/>
2724   </c>
2725   <c>413</c>
2726   <c>Request Entity Too Large</c>
2727   <c>
2728      <xref target="status.413"/>
2729   </c>
2730   <c>414</c>
[465]2731   <c>URI Too Long</c>
[255]2732   <c>
2733      <xref target="status.414"/>
2734   </c>
2735   <c>415</c>
2736   <c>Unsupported Media Type</c>
2737   <c>
2738      <xref target="status.415"/>
2739   </c>
2740   <c>417</c>
2741   <c>Expectation Failed</c>
2742   <c>
2743      <xref target="status.417"/>
2744   </c>
[1071]2745   <c>426</c>
2746   <c>Upgrade Required</c>
2747   <c>
2748      <xref target="status.426"/>
2749   </c>
[255]2750   <c>500</c>
2751   <c>Internal Server Error</c>
2752   <c>
2753      <xref target="status.500"/>
2754   </c>
2755   <c>501</c>
2756   <c>Not Implemented</c>
2757   <c>
2758      <xref target="status.501"/>
2759   </c>
2760   <c>502</c>
2761   <c>Bad Gateway</c>
2762   <c>
2763      <xref target="status.502"/>
2764   </c>
2765   <c>503</c>
2766   <c>Service Unavailable</c>
2767   <c>
2768      <xref target="status.503"/>
2769   </c>
2770   <c>504</c>
2771   <c>Gateway Timeout</c>
2772   <c>
2773      <xref target="status.504"/>
2774   </c>
2775   <c>505</c>
2776   <c>HTTP Version Not Supported</c>
2777   <c>
2778      <xref target="status.505"/>
2779   </c>
[682]2782<?ENDINC p2-semantics.iana-status-codes ?>
[921]2784<section title="Header Field Registration" anchor="header.field.registration">
[969]2786   The Message Header Field Registry located at <eref target=""/> shall be updated
[290]2787   with the permanent registrations below (see <xref target="RFC3864"/>):
[680]2789<?BEGININC p2-semantics.iana-headers ?>
[253]2790<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
[290]2791<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
[253]2792   <ttcol>Header Field Name</ttcol>
2793   <ttcol>Protocol</ttcol>
2794   <ttcol>Status</ttcol>
2795   <ttcol>Reference</ttcol>
[253]2797   <c>Allow</c>
2798   <c>http</c>
2799   <c>standard</c>
2800   <c>
2801      <xref target="header.allow"/>
2802   </c>
2803   <c>Expect</c>
2804   <c>http</c>
2805   <c>standard</c>
2806   <c>
2807      <xref target="header.expect"/>
2808   </c>
2809   <c>From</c>
2810   <c>http</c>
2811   <c>standard</c>
2812   <c>
2813      <xref target="header.from"/>
2814   </c>
2815   <c>Location</c>
2816   <c>http</c>
2817   <c>standard</c>
2818   <c>
2819      <xref target="header.location"/>
2820   </c>
2821   <c>Max-Forwards</c>
2822   <c>http</c>
2823   <c>standard</c>
2824   <c>
2825      <xref target="header.max-forwards"/>
2826   </c>
2827   <c>Referer</c>
2828   <c>http</c>
2829   <c>standard</c>
2830   <c>
2831      <xref target="header.referer"/>
2832   </c>
2833   <c>Retry-After</c>
2834   <c>http</c>
2835   <c>standard</c>
2836   <c>
2837      <xref target="header.retry-after"/>
2838   </c>
2839   <c>Server</c>
2840   <c>http</c>
2841   <c>standard</c>
2842   <c>
2843      <xref target="header.server"/>
2844   </c>
2845   <c>User-Agent</c>
2846   <c>http</c>
2847   <c>standard</c>
2848   <c>
2849      <xref target="header.user-agent"/>
2850   </c>
[680]2853<?ENDINC p2-semantics.iana-headers ?>
[290]2855   The change controller is: "IETF ( - Internet Engineering Task Force".
[8]2860<section title="Security Considerations" anchor="security.considerations">
2862   This section is meant to inform application developers, information
2863   providers, and users of the security limitations in HTTP/1.1 as
2864   described by this document. The discussion does not include
2865   definitive solutions to the problems revealed, though it does make
2866   some suggestions for reducing security risks.
2869<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2871   Like any generic data transfer protocol, HTTP cannot regulate the
2872   content of the data that is transferred, nor is there any a priori
2873   method of determining the sensitivity of any particular piece of
2874   information within the context of any given request. Therefore,
2875   applications &SHOULD; supply as much control over this information as
2876   possible to the provider of that information. Four header fields are
2877   worth special mention in this context: Server, Via, Referer and From.
2880   Revealing the specific software version of the server might allow the
2881   server machine to become more vulnerable to attacks against software
2882   that is known to contain security holes. Implementors &SHOULD; make the
2883   Server header field a configurable option.
2886   Proxies which serve as a portal through a network firewall &SHOULD;
2887   take special precautions regarding the transfer of header information
2888   that identifies the hosts behind the firewall. In particular, they
2889   &SHOULD; remove, or replace with sanitized versions, any Via fields
2890   generated behind the firewall.
[994]2893   The Referer header field allows reading patterns to be studied and reverse
[8]2894   links drawn. Although it can be very useful, its power can be abused
2895   if user details are not separated from the information contained in
2896   the Referer. Even when the personal information has been removed, the
[994]2897   Referer header field might indicate a private document's URI whose
[8]2898   publication would be inappropriate.
2901   The information sent in the From field might conflict with the user's
2902   privacy interests or their site's security policy, and hence it
2903   &SHOULD-NOT;  be transmitted without the user being able to disable,
2904   enable, and modify the contents of the field. The user &MUST; be able
2905   to set the contents of this field within a user preference or
2906   application defaults configuration.
2909   We suggest, though do not require, that a convenient toggle interface
2910   be provided for the user to enable or disable the sending of From and
2911   Referer information.
[1036]2914   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2915   target="header.server"/>) header fields can sometimes be used to determine
2916   that a specific client or server have a particular security hole which might
2917   be exploited. Unfortunately, this same information is often used for other
2918   valuable purposes for which HTTP currently has no better mechanism.
2921   Furthermore, the User-Agent header field may contain enough entropy to be
2922   used, possibly in conjunction with other material, to uniquely identify the
2923   user.
[1161]2926   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
[994]2927   that was sent in request header fields within the body of their response.
[666]2928   Clients &SHOULD; be careful with sensitive information, like Cookies,
[1161]2929   Authorization credentials, and other header fields that might be used to
[666]2930   collect data from the client.
[184]2934<section title="Encoding Sensitive Information in URIs" anchor="">
2936   Because the source of a link might be private information or might
2937   reveal an otherwise private information source, it is strongly
2938   recommended that the user be able to select whether or not the
2939   Referer field is sent. For example, a browser client could have a
2940   toggle switch for browsing openly/anonymously, which would
2941   respectively enable/disable the sending of Referer and From
2942   information.
[172]2945   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
[8]2946   HTTP request if the referring page was transferred with a secure
2947   protocol.
[969]2950   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2951   sensitive data because that data will be placed in the request-target. Many
[823]2952   existing servers, proxies, and user agents log or display the request-target
2953   in places where it might be visible to third parties. Such services can
[172]2954   use POST-based form submission instead.
2958<section title="Location Headers and Spoofing" anchor="location.spoofing">
2960   If a single server supports multiple organizations that do not trust
2961   one another, then it &MUST; check the values of Location and Content-Location
[994]2962   header fields in responses that are generated under control of
[8]2963   said organizations to make sure that they do not attempt to
2964   invalidate resources over which they have no authority.
[1061]2968<section title="Security Considerations for CONNECT">
2970   Since tunneled data is opaque to the proxy, there are additional
2971   risks to tunneling to other well-known or reserved ports.
2972   A HTTP client CONNECTing to port 25 could relay spam
2973   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2974   access to a small number of known ports.
[8]2980<section title="Acknowledgments" anchor="ack">
[119]2985<references title="Normative References">
[31]2987<reference anchor="Part1">
[119]2988  <front>
2989    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2990    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]2991      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]2992      <address><email></email></address>
2993    </author>
2994    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]2995      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2996      <address><email></email></address>
[119]2997    </author>
2998    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2999      <organization abbrev="HP">Hewlett-Packard Company</organization>
3000      <address><email></email></address>
3001    </author>
3002    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3003      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3004      <address><email></email></address>
3005    </author>
3006    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3007      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3008      <address><email></email></address>
3009    </author>
3010    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3011      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3012      <address><email></email></address>
3013    </author>
3014    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3015      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3016      <address><email></email></address>
3017    </author>
3018    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3019      <organization abbrev="W3C">World Wide Web Consortium</organization>
3020      <address><email></email></address>
3021    </author>
3022    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3023      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3024      <address><email></email></address>
3025    </author>
3026    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3027  </front>
3028  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3029  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3032<reference anchor="Part3">
[119]3033  <front>
3034    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3035    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3036      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3037      <address><email></email></address>
3038    </author>
3039    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3040      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3041      <address><email></email></address>
[119]3042    </author>
3043    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3044      <organization abbrev="HP">Hewlett-Packard Company</organization>
3045      <address><email></email></address>
3046    </author>
3047    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3048      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3049      <address><email></email></address>
3050    </author>
3051    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3052      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3053      <address><email></email></address>
3054    </author>
3055    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3056      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3057      <address><email></email></address>
3058    </author>
3059    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3060      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3061      <address><email></email></address>
3062    </author>
3063    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3064      <organization abbrev="W3C">World Wide Web Consortium</organization>
3065      <address><email></email></address>
3066    </author>
3067    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3068      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3069      <address><email></email></address>
3070    </author>
3071    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3072  </front>
3073  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3074  <x:source href="p3-payload.xml" basename="p3-payload"/>
3077<reference anchor="Part4">
[119]3078  <front>
3079    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3080    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3081      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3082      <address><email></email></address>
3083    </author>
3084    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3085      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3086      <address><email></email></address>
[119]3087    </author>
3088    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3089      <organization abbrev="HP">Hewlett-Packard Company</organization>
3090      <address><email></email></address>
3091    </author>
3092    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3093      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3094      <address><email></email></address>
3095    </author>
3096    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3097      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3098      <address><email></email></address>
3099    </author>
3100    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3101      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3102      <address><email></email></address>
3103    </author>
3104    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3105      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3106      <address><email></email></address>
3107    </author>
3108    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3109      <organization abbrev="W3C">World Wide Web Consortium</organization>
3110      <address><email></email></address>
3111    </author>
3112    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3113      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3114      <address><email></email></address>
3115    </author>
3116    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3117  </front>
3118  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3119  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3122<reference anchor="Part5">
[119]3123  <front>
3124    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3125    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3126      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3127      <address><email></email></address>
3128    </author>
3129    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3130      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3131      <address><email></email></address>
[119]3132    </author>
3133    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3134      <organization abbrev="HP">Hewlett-Packard Company</organization>
3135      <address><email></email></address>
3136    </author>
3137    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3138      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3139      <address><email></email></address>
3140    </author>
3141    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3142      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3143      <address><email></email></address>
3144    </author>
3145    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3146      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3147      <address><email></email></address>
3148    </author>
3149    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3150      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3151      <address><email></email></address>
3152    </author>
3153    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3154      <organization abbrev="W3C">World Wide Web Consortium</organization>
3155      <address><email></email></address>
3156    </author>
3157    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3158      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3159      <address><email></email></address>
3160    </author>
3161    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3162  </front>
3163  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3164  <x:source href="p5-range.xml" basename="p5-range"/>
3167<reference anchor="Part6">
[119]3168  <front>
3169    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3170    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3171      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3172      <address><email></email></address>
3173    </author>
3174    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3175      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3176      <address><email></email></address>
[119]3177    </author>
3178    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3179      <organization abbrev="HP">Hewlett-Packard Company</organization>
3180      <address><email></email></address>
3181    </author>
3182    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3183      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3184      <address><email></email></address>
3185    </author>
3186    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3187      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3188      <address><email></email></address>
3189    </author>
3190    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3191      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3192      <address><email></email></address>
3193    </author>
3194    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3195      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3196      <address><email></email></address>
3197    </author>
3198    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3199      <organization abbrev="W3C">World Wide Web Consortium</organization>
3200      <address><email></email></address>
3201    </author>
[601]3202    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3203      <address><email></email></address>
3204    </author>
[119]3205    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3206      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3207      <address><email></email></address>
3208    </author>
3209    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3210  </front>
3211  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3212  <x:source href="p6-cache.xml" basename="p6-cache"/>
3215<reference anchor="Part7">
[119]3216  <front>
3217    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3218    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
[1106]3219      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3220      <address><email></email></address>
3221    </author>
3222    <author initials="J." surname="Gettys" fullname="Jim Gettys">
[844]3223      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3224      <address><email></email></address>
[119]3225    </author>
3226    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3227      <organization abbrev="HP">Hewlett-Packard Company</organization>
3228      <address><email></email></address>
3229    </author>
3230    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3231      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3232      <address><email></email></address>
3233    </author>
3234    <author initials="L." surname="Masinter" fullname="Larry Masinter">
[1106]3235      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
[119]3236      <address><email></email></address>
3237    </author>
3238    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3239      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3240      <address><email></email></address>
3241    </author>
3242    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3243      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3244      <address><email></email></address>
3245    </author>
3246    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3247      <organization abbrev="W3C">World Wide Web Consortium</organization>
3248      <address><email></email></address>
3249    </author>
3250    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3251      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3252      <address><email></email></address>
3253    </author>
3254    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3255  </front>
3256  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3257  <x:source href="p7-auth.xml" basename="p7-auth"/>
[119]3260<reference anchor="RFC2119">
3261  <front>
3262    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3263    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3264      <organization>Harvard University</organization>
3265      <address><email></email></address>
3266    </author>
3267    <date month="March" year="1997"/>
3268  </front>
3269  <seriesInfo name="BCP" value="14"/>
3270  <seriesInfo name="RFC" value="2119"/>
[785]3273<reference anchor="RFC3986">
3274 <front>
3275  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3276  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3277    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3278    <address>
3279       <email></email>
3280       <uri></uri>
3281    </address>
3282  </author>
3283  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3284    <organization abbrev="Day Software">Day Software</organization>
3285    <address>
3286      <email></email>
3287      <uri></uri>
3288    </address>
3289  </author>
3290  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3291    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3292    <address>
3293      <email></email>
3294      <uri></uri>
3295    </address>
3296  </author>
3297  <date month='January' year='2005'></date>
3298 </front>
[1003]3299 <seriesInfo name="STD" value="66"/>
[785]3300 <seriesInfo name="RFC" value="3986"/>
[425]3303<reference anchor="RFC5234">
3304  <front>
3305    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3306    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3307      <organization>Brandenburg InternetWorking</organization>
3308      <address>
[728]3309        <email></email>
3310      </address> 
[425]3311    </author>
3312    <author initials="P." surname="Overell" fullname="Paul Overell">
3313      <organization>THUS plc.</organization>
3314      <address>
[728]3315        <email></email>
3316      </address>
[425]3317    </author>
3318    <date month="January" year="2008"/>
3319  </front>
3320  <seriesInfo name="STD" value="68"/>
3321  <seriesInfo name="RFC" value="5234"/>
3326<references title="Informative References">
[129]3328<reference anchor="RFC1945">
3329  <front>
3330    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3331    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3332      <organization>MIT, Laboratory for Computer Science</organization>
3333      <address><email></email></address>
3334    </author>
3335    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3336      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3337      <address><email></email></address>
3338    </author>
3339    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3340      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3341      <address><email></email></address>
3342    </author>
3343    <date month="May" year="1996"/>
3344  </front>
3345  <seriesInfo name="RFC" value="1945"/>
[119]3348<reference anchor="RFC2068">
3349  <front>
3350    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3351    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3352      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3353      <address><email></email></address>
3354    </author>
3355    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3356      <organization>MIT Laboratory for Computer Science</organization>
3357      <address><email></email></address>
3358    </author>
3359    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3360      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3361      <address><email></email></address>
3362    </author>
3363    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3364      <organization>MIT Laboratory for Computer Science</organization>
3365      <address><email></email></address>
3366    </author>
3367    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3368      <organization>MIT Laboratory for Computer Science</organization>
3369      <address><email></email></address>
3370    </author>
3371    <date month="January" year="1997"/>
3372  </front>
3373  <seriesInfo name="RFC" value="2068"/>
[36]3376<reference anchor="RFC2616">
[119]3377  <front>
3378    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3379    <author initials="R." surname="Fielding" fullname="R. Fielding">
3380      <organization>University of California, Irvine</organization>
3381      <address><email></email></address>
3382    </author>
3383    <author initials="J." surname="Gettys" fullname="J. Gettys">
3384      <organization>W3C</organization>
3385      <address><email></email></address>
3386    </author>
3387    <author initials="J." surname="Mogul" fullname="J. Mogul">
3388      <organization>Compaq Computer Corporation</organization>
3389      <address><email></email></address>
3390    </author>
3391    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3392      <organization>MIT Laboratory for Computer Science</organization>
3393      <address><email></email></address>
3394    </author>
3395    <author initials="L." surname="Masinter" fullname="L. Masinter">
3396      <organization>Xerox Corporation</organization>
3397      <address><email></email></address>
3398    </author>
3399    <author initials="P." surname="Leach" fullname="P. Leach">
3400      <organization>Microsoft Corporation</organization>
3401      <address><email></email></address>
3402    </author>
3403    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3404      <organization>W3C</organization>
3405      <address><email></email></address>
3406    </author>
3407    <date month="June" year="1999"/>
3408  </front>
3409  <seriesInfo name="RFC" value="2616"/>
[255]3412<reference anchor='RFC2817'>
3413  <front>
3414    <title>Upgrading to TLS Within HTTP/1.1</title>
3415    <author initials='R.' surname='Khare' fullname='R. Khare'>
3416      <organization>4K Associates / UC Irvine</organization>
3417      <address><email></email></address>
3418    </author>
3419    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3420      <organization>Agranat Systems, Inc.</organization>
3421      <address><email></email></address>
3422    </author>
3423    <date year='2000' month='May' />
3424  </front>
3425  <seriesInfo name='RFC' value='2817' />
[253]3428<reference anchor='RFC3864'>
3429  <front>
3430    <title>Registration Procedures for Message Header Fields</title>
3431    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3432      <organization>Nine by Nine</organization>
3433      <address><email></email></address>
3434    </author>
3435    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3436      <organization>BEA Systems</organization>
3437      <address><email></email></address>
3438    </author>
3439    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3440      <organization>HP Labs</organization>
3441      <address><email></email></address>
3442    </author>
3443    <date year='2004' month='September' />
3444  </front>
3445  <seriesInfo name='BCP' value='90' />
3446  <seriesInfo name='RFC' value='3864' />
[262]3449<reference anchor='RFC5226'>
3450  <front>
3451    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3452    <author initials='T.' surname='Narten' fullname='T. Narten'>
3453      <organization>IBM</organization>
3454      <address><email></email></address>
3455    </author>
3456    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3457      <organization>Google</organization>
3458      <address><email></email></address>
3459    </author>
3460    <date year='2008' month='May' />
3461  </front>
3462  <seriesInfo name='BCP' value='26' />
3463  <seriesInfo name='RFC' value='5226' />
[327]3466<reference anchor="RFC5322">
3467  <front>
3468    <title>Internet Message Format</title>
3469    <author initials="P." surname="Resnick" fullname="P. Resnick">
3470      <organization>Qualcomm Incorporated</organization>
3471    </author>
3472    <date year="2008" month="October"/>
3473  </front>
3474  <seriesInfo name="RFC" value="5322"/>
[1158]3477<reference anchor='RFC5789'>
3478  <front>
3479    <title>PATCH Method for HTTP</title>
3480    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3481      <organization>Linden Lab</organization>
3482    </author>
[1160]3483    <author initials='J.' surname='Snell' fullname='J. Snell' />
[1158]3484    <date year='2010' month='March' />
3485  </front>
3486  <seriesInfo name='RFC' value='5789' />
[99]3491<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
[262]3493  This document takes over the Status Code Registry, previously defined
3494  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3495  (<xref target="status.code.registry"/>)
[108]3498  Clarify definition of POST.
3499  (<xref target="POST"/>)
[1160]3502  Remove requirement to handle all Content-* header fields; ban use of
3503  Content-Range with PUT.
3504  (<xref target="PUT"/>)
[1066]3507  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3508  (<xref target="CONNECT"/>)
[109]3511  Failed to consider that there are
3512  many other request methods that are safe to automatically redirect,
3513  and further that the user agent is able to make that determination
3514  based on the request method semantics.
3515  (Sections <xref format="counter" target="status.301"/>,
3516  <xref format="counter" target="status.302"/> and
[233]3517  <xref format="counter" target="status.307"/>)
[235]3520  Deprecate 305 Use Proxy status code, because user agents did not implement it.
[965]3521  It used to indicate that the target resource must be accessed through the
[235]3522  proxy given by the Location field. The Location field gave the URI of the
3523  proxy. The recipient was expected to repeat this single request via the proxy.
3524  (<xref target="status.305"/>)
[1071]3527  Define status 426 (Upgrade Required) (this was incorporated from
3528  <xref target="RFC2817"/>).
3529  (<xref target="status.426"/>)
[1235]3532  Change ABNF productions for header fields to only define the field value.
3533  (<xref target="header.fields"/>)
[994]3536  Reclassify "Allow" as response header field, removing the option to
[232]3537  specify it in a PUT request.
[994]3538  Relax the server requirement on the contents of the Allow header field and
3539  remove requirement on clients to always trust the header field value.
[232]3540  (<xref target="header.allow"/>)
[994]3543  Correct syntax of Location header field to allow URI references (including
[785]3544  relative references and fragments), as referred symbol "absoluteURI" wasn't
3545  what was expected, and add some clarifications as to when use of fragments
3546  would not be appropriate.
[114]3547  (<xref target="header.location"/>)
[1070]3550  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3551  extension methods could have used it as well).
3552  (<xref target="header.max-forwards"/>)
[994]3555  Allow Referer field value of "about:blank" as alternative to not specifying it.
[593]3556  (<xref target="header.referer"/>)
[994]3559  In the description of the Server header field, the Via field
[112]3560  was described as a SHOULD. The requirement was and is stated
[994]3561  correctly in the description of the Via header field in &header-via;.
[112]3562  (<xref target="header.server"/>)
[680]3566<?BEGININC p2-semantics.abnf-appendix ?>
[427]3567<section xmlns:x="" title="Collected ABNF" anchor="collected.abnf">
3569<artwork type="abnf" name="p2-semantics.parsed-abnf">
[1235]3570<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
[1235]3572<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
[1235]3574<x:ref>From</x:ref> = mailbox
[678]3576<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
[1235]3578<x:ref>Location</x:ref> = URI-reference
[1235]3580<x:ref>Max-Forwards</x:ref> = 1*DIGIT
[1128]3581<x:ref>Method</x:ref> = token
[427]3583<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3585<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3586<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
[1235]3587<x:ref>Referer</x:ref> = absolute-URI / partial-URI
3588<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
[1235]3590<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
[1124]3591<x:ref>Status-Code</x:ref> = 3DIGIT
[785]3593<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
[1235]3594<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
[648]3596<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
[688]3598<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3600<x:ref>delta-seconds</x:ref> = 1*DIGIT
3602<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3603<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3604<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
[425]3605 *expect-params ]
3607<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3609<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
[648]3611<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
[678]3612<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3614<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3616<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
[532]3619<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
[1138]3620; Allow defined but not used
3621; Expect defined but not used
3622; From defined but not used
3623; Location defined but not used
3624; Max-Forwards defined but not used
[532]3625; Reason-Phrase defined but not used
[1138]3626; Referer defined but not used
3627; Retry-After defined but not used
3628; Server defined but not used
[425]3629; Status-Code defined but not used
[1138]3630; User-Agent defined but not used
[680]3632<?ENDINC p2-semantics.abnf-appendix ?>
[252]3634<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
[1002]3636<section title="Since RFC 2616">
3638  Extracted relevant partitions from <xref target="RFC2616"/>.
3642<section title="Since draft-ietf-httpbis-p2-semantics-00">
[116]3644  Closed issues:
3645  <list style="symbols">
3646    <t>
[324]3647      <eref target=""/>:
[116]3648      "Via is a MUST"
3649      (<eref target=""/>)
3650    </t>
3651    <t>
[324]3652      <eref target=""/>:
[116]3653      "Fragments allowed in Location"
3654      (<eref target=""/>)
3655    </t>
3656    <t>
[324]3657      <eref target=""/>:
[116]3658      "Safe Methods vs Redirection"
3659      (<eref target=""/>)
3660    </t>
3661    <t>
[324]3662      <eref target=""/>:
[116]3663      "Revise description of the POST method"
3664      (<eref target=""/>)
3665    </t>
3666    <t>
[324]3667      <eref target=""/>:
[152]3668      "Normative and Informative references"
3669    </t>
3670    <t>
[324]3671      <eref target=""/>:
[116]3672      "RFC2606 Compliance"
3673    </t>
[129]3674    <t>
[324]3675      <eref target=""/>:
[129]3676      "Informative references"
3677    </t>
[130]3678    <t>
[324]3679      <eref target=""/>:
[130]3680      "Redundant cross-references"
3681    </t>
[116]3682  </list>
3685  Other changes:
3686  <list style="symbols">
3687    <t>
3688      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3689    </t>
3690  </list>
[170]3694<section title="Since draft-ietf-httpbis-p2-semantics-01">
[180]3696  Closed issues:
3697  <list style="symbols">
3698    <t>
[324]3699      <eref target=""/>:
[180]3700      "PUT side effects"
3701    </t>
[201]3702    <t>
[324]3703      <eref target=""/>:
[201]3704      "Duplicate Host header requirements"
3705    </t>
[180]3706  </list>
[324]3709  Ongoing work on ABNF conversion (<eref target=""/>):
[190]3710  <list style="symbols">
3711    <t>
3712      Move "Product Tokens" section (back) into Part 1, as "token" is used
[994]3713      in the definition of the Upgrade header field.
[190]3714    </t>
[205]3715    <t>
3716      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3717    </t>
[210]3718    <t>
[212]3719      Copy definition of delta-seconds from Part6 instead of referencing it.
[210]3720    </t>
[190]3721  </list>
[252]3725<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
[232]3727  Closed issues:
3728  <list style="symbols">
3729    <t>
[324]3730      <eref target=""/>:
[240]3731      "Requiring Allow in 405 responses"
3732    </t>
3733    <t>
[324]3734      <eref target=""/>:
[262]3735      "Status Code Registry"
3736    </t>
3737    <t>
[324]3738      <eref target=""/>:
[237]3739      "Redirection vs. Location"
3740    </t>
3741    <t>
[324]3742      <eref target=""/>:
[242]3743      "Cacheability of 303 response"
3744    </t>
3745    <t>
[324]3746      <eref target=""/>:
[236]3747      "305 Use Proxy"
3748    </t>
3749    <t>
[324]3750      <eref target=""/>:
[232]3751      "Classification for Allow header"
3752    </t>
[241]3753    <t>
[324]3754      <eref target=""/>:
[241]3755      "PUT - 'store under' vs 'store at'"
3756    </t>
[232]3757  </list>
[994]3760  Ongoing work on IANA Message Header Field Registration (<eref target=""/>):
[253]3761  <list style="symbols">
3762    <t>
[994]3763      Reference RFC 3984, and update header field registrations for headers defined
[253]3764      in this document.
3765    </t>
3766  </list>
[324]3769  Ongoing work on ABNF conversion (<eref target=""/>):
[260]3770  <list style="symbols">
3771    <t>
3772      Replace string literals when the string really is case-sensitive (method).
3773    </t>
3774  </list>
[267]3778<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
[274]3780  Closed issues:
3781  <list style="symbols">
3782    <t>
[324]3783      <eref target=""/>:
[280]3784      "OPTIONS request bodies"
3785    </t>
3786    <t>
[324]3787      <eref target=""/>:
[274]3788      "Description of CONNECT should refer to RFC2817"
3789    </t>
[300]3790    <t>
[324]3791      <eref target=""/>:
[300]3792      "Location Content-Location reference request/response mixup"
3793    </t>
[274]3794  </list>
[324]3797  Ongoing work on Method Registry (<eref target=""/>):
[270]3798  <list style="symbols">
3799    <t>
3800      Added initial proposal for registration process, plus initial
3801      content (non-HTTP/1.1 methods to be added by a separate specification).
3802    </t>
3803  </list>
[323]3807<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
[327]3809  Closed issues:
3810  <list style="symbols">
3811    <t>
[333]3812      <eref target=""/>:
3813      "Content-*"
3814    </t>
3815    <t>
[327]3816      <eref target=""/>:
3817      "RFC 2822 is updated by RFC 5322"
3818    </t>
3819  </list>
3822  Ongoing work on ABNF conversion (<eref target=""/>):
3823  <list style="symbols">
3824    <t>
3825      Use "/" instead of "|" for alternatives.
3826    </t>
[356]3827    <t>
3828      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
[357]3829      whitespace ("OWS") and required whitespace ("RWS").
[356]3830    </t>
3831    <t>
[357]3832      Rewrite ABNFs to spell out whitespace rules, factor out
[994]3833      header field value format definitions.
[356]3834    </t>
[334]3835  </list>
[382]3839<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
[398]3841  Closed issues:
3842  <list style="symbols">
3843    <t>
3844      <eref target=""/>:
3845      "Reason-Phrase BNF"
3846    </t>
3847  </list>
[543]3850  Final work on ABNF conversion (<eref target=""/>):
[421]3851  <list style="symbols">
3852    <t>
[424]3853      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
[421]3854    </t>
3855  </list>
[547]3859<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
[579]3861  Closed issues:
3862  <list style="symbols">
3863    <t>
[593]3864      <eref target=""/>:
3865      "Clarify when Referer is sent"
3866    </t>
3867    <t>
[579]3868      <eref target=""/>:
3869      "status codes vs methods"
3870    </t>
[591]3871    <t>
3872      <eref target=""/>:
3873      "Do not require "updates" relation for specs that register status codes or method names"
3874    </t>
[579]3875  </list>
[604]3879<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
[614]3881  Closed issues:
3882  <list style="symbols">
3883    <t>
[658]3884      <eref target=""/>:
3885      "Idempotency"
3886    </t>
3887    <t>
3888      <eref target=""/>:
3889      "TRACE security considerations"
3890    </t>
3891    <t>
[695]3892      <eref target=""/>:
3893      "Clarify rules for determining what entities a response carries"
3894    </t>
3895    <t>
[614]3896      <eref target=""/>:
3897      "update note citing RFC 1945 and 2068"
3898    </t>
[629]3899    <t>
3900      <eref target=""/>:
3901      "update note about redirect limit"
3902    </t>
[632]3903    <t>
3904      <eref target=""/>:
3905      "Location header ABNF should use 'URI'"
3906    </t>
[665]3907    <t>
3908      <eref target=""/>:
3909      "fragments in Location vs status 303"
3910    </t>
[700]3911    <t>
3912      <eref target=""/>:
3913      "move IANA registrations for optional status codes"
3914    </t>
[614]3915  </list>
3918  Partly resolved issues:
3919  <list style="symbols">
3920    <t>
3921      <eref target=""/>:
3922      "Are OPTIONS and TRACE safe?"
3923    </t>
3924  </list>
[720]3928<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
[759]3930  Closed issues:
3931  <list style="symbols">
3932    <t>
3933      <eref target=""/>:
3934      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3935      status codes when fixing this previously)
3936    </t>
3937  </list>
[773]3941<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
[785]3943  Closed issues:
3944  <list style="symbols">
3945    <t>
3946      <eref target=""/>:
3947      "Fragment combination / precedence during redirects"
3948    </t>
3949  </list>
3952  Partly resolved issues:
3953  <list style="symbols">
3954    <t>
3955      <eref target=""/>:
3956      "Location header payload handling"
3957    </t>
[823]3958    <t>
3959      <eref target=""/>:
3960      "Term for the requested resource's URI"
3961    </t>
[785]3962  </list>
[841]3966<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
[858]3968  Closed issues:
3969  <list style="symbols">
3970    <t>
3971      <eref target=""/>:
3972      "Clarify 'Requested Variant'"
3973    </t>
3974    <t>
3975      <eref target=""/>:
3976      "Clarify entity / representation / variant terminology"
3977    </t>
[886]3978    <t>
[889]3979      <eref target=""/>:
3980      "Methods and Caching"
3981    </t>
3982    <t>
[895]3983      <eref target=""/>:
3984      "OPTIONS vs Max-Forwards"
3985    </t>
3986    <t>
[886]3987      <eref target=""/>:
3988      "Status codes and caching"
3989    </t>
[911]3990    <t>
3991      <eref target=""/>:
3992      "consider removing the 'changes from 2068' sections"
3993    </t>
[858]3994  </list>
[973]3998<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
[1036]4000  Closed issues:
4001  <list style="symbols">
4002    <t>
[1038]4003      <eref target=""/>:
4004      "Considerations for new status codes"
4005    </t>
4006    <t>
[1037]4007      <eref target=""/>:
4008      "Considerations for new methods"
4009    </t>
4010    <t>
[1036]4011      <eref target=""/>:
4012      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4013    </t>
4014  </list>
[1052]4018<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
[1058]4020  Closed issues:
4021  <list style="symbols">
4022    <t>
[1097]4023      <eref target=""/>:
4024      "Fragment combination / precedence during redirects" (added warning
4025      about having a fragid on the redirect may cause inconvenience in
4026      some cases)
4027    </t>
4028    <t>
[1160]4029      <eref target=""/>:
4030      "Content-* vs. PUT"
4031    </t>
4032    <t>
[1058]4033      <eref target=""/>:
4034      "205 Bodies"
4035    </t>
[1061]4036    <t>
[1160]4037      <eref target=""/>:
4038      "Understanding Content-* on non-PUT requests"
4039    </t>
4040    <t>
4041      <eref target=""/>:
4042      "Content-*"
4043    </t>
4044    <t>
4045      <eref target=""/>:
4046      "Header type defaulting"
4047    </t>
4048    <t>
4049      <eref target=""/>:
4050      "PUT - 'store under' vs 'store at'"
4051    </t>
4052    <t>
[1154]4053      <eref target=""/>:
4054      "duplicate ABNF for Reason-Phrase"
4055    </t>
4056    <t>
[1160]4057      <eref target=""/>:
4058      "Note special status of Content-* prefix in header registration procedures"
4059    </t>
4060    <t>
[1070]4061      <eref target=""/>:
4062      "Max-Forwards vs extension methods"
4063    </t>
4064    <t>
[1154]4065      <eref target=""/>:
4066      "What is the value space of HTTP status codes?" (actually fixed in
4067      draft-ietf-httpbis-p2-semantics-11)
[1124]4068    </t>
4069    <t>
[1165]4070      <eref target=""/>:
4071      "Header Classification"
4072    </t>
4073    <t>
4074      <eref target=""/>:
4075      "PUT side effect: invalidation or just stale?"
4076    </t>
4077    <t>
[1068]4078      <eref target=""/>:
4079      "proxies not supporting certain methods"
4080    </t>
4081    <t>
[1061]4082      <eref target=""/>:
4083      "Migrate CONNECT from RFC2817 to p2"
4084    </t>
[1071]4085    <t>
4086      <eref target=""/>:
4087      "Migrate Upgrade details from RFC2817"
4088    </t>
[1111]4089    <t>
[1228]4090      <eref target=""/>:
[1160]4091      "clarify PUT semantics'"
4092    </t>
4093    <t>
[1128]4094      <eref target=""/>:
4095      "duplicate ABNF for 'Method'"
4096    </t>
[1138]4097    <t>
4098      <eref target=""/>:
4099      "untangle ABNFs for header fields"
4100    </t>
[1058]4101  </list>
[1180]4105<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
[1235]4107  Closed issues:
4108  <list style="symbols">
4109    <t>
4110      <eref target=""/>:
4111      "untangle ABNFs for header fields"
4112    </t>
[1261]4113    <t>
4114      <eref target=""/>:
4115      "message-body in CONNECT request"
4116    </t>
[1235]4117  </list>
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