HTTP                                                          J. Reschke
Internet-Draft                                                greenbytes
Updates: 5323 (if approved)                                  A. Malhotra
Intended status: Standards Track
Expires: 2 October 10 December 2021                                     J.M. Snell
                                                           31 March
                                                             8 June 2021

                           HTTP SEARCH Method


   This specification updates the definition and semantics of the HTTP
   SEARCH request method originally defined by RFC 5323.

Editorial Note

   This note is to be removed before publishing as an RFC.

   Discussion of this draft takes place on the HTTP working group
   mailing list (, which is archived at

   This note is to be removed before publishing as an RFC.

   Working Group information can be found at; source
   code and issues list for this draft can be found at

   The changes in this draft are summarized in Appendix A.1.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 2 October 10 December 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  SEARCH  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  The "Accept-Search" Header Field  . . . . . . . . . . . . . .   5
   4.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Simple SEARCH with a Direct Response  . . . . . . . . . .   6
     4.2.  Simple SEARCH with indirect response (303 See Other)  . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .   8
     A.1.  Since draft-ietf-httpbis-safe-method-w-body-00  . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8   9

1.  Introduction

   This specification updates the HTTP SEARCH method originally defined
   in [RFC5323].

   Many existing HTTP-based applications use the HTTP GET and POST
   methods in various ways to implement the functionality provided by

   Using a GET request with some combination of query parameters
   included within the request URI (as illustrated in the example below)
   is arguably the most common mechanism for implementing search in web
   applications.  With this approach, implementations are required to
   parse the request URI into distinct path (everything before the '?')
   and query elements (everything after the '?').  The path identifies
   the resource processing the query (in this case '
   feed') while the query identifies the specific parameters of the
   search operation.

   A typical use of HTTP GET for requesting a search

   GET /feed?q=foo&limit=10&sort=-published HTTP/1.1

   While there are definite advantages to using GET requests in this
   manner, the disadvantages should not be overlooked.  Specifically:

   *  Without specific knowledge of the resource and server to which the
      GET request is being sent, there is no way for the client to know
      that a search operation is being requested.  Identical requests
      sent to two different servers can implement entirely different

   *  Encoding query parameters directly into the request URI
      effectively casts every possible combination of query inputs as
      distinct resources.  For instance, because mechanisms such as HTTP
      caching handle request URIs as opaque character sequences, queries
      such as '' and
      '' will be treated as entirely separate
      resources even if they yield identical results.

   *  While most modern browser and server implementations allow for
      long request URIs, there is no standardized minimum or maximum
      length for URIs in general.  Many resource constrained devices
      enforce strict limits on the maximum number of characters that can
      be included in a URI.  Such limits can prove impractical for large
      or complex query parameters.

   *  Query expressions included within a request URI must either be
      restricted to relatively simple key value pairs or encoded such
      that the query can be safely represented in the limited character-
      set allowed by URL standards.  Such encoding can add significant
      complexity, introduce bugs, or otherwise reduce the overall
      visibility of the query being requested.

   As an alternative to using GET, many implementations make use of the
   HTTP POST method to perform queries, as illustrated in the example
   below.  In this case, the input parameters to the search operation
   are passed along within the request payload as opposed to using the
   request URI.

   A typical use of HTTP POST for requesting a search
   POST /feed HTTP/1.1
   Content-Type: application/x-www-form-urlencoded


   This variation, however, suffers from the same basic limitation as
   GET in that it is not readily apparent -- absent specific knowledge
   of the resource and server to which the request is being sent -- that
   a search operation is what is being requested.  Web applications use
   the POST method for a wide variety of uses including the creation or
   modification of existing resources.  Sending the request above to a
   different server, or even repeatedly sending the request to the same
   server could have dramatically different effects.

   The SEARCH method provides a solution that spans the gap between the
   use of GET and POST.  As with POST, the input to the query operation
   is passed along within the payload of the request rather than as part
   of the request URI.  Unlike POST, however the semantics of the SEARCH
   method are specifically defined.

   In this document, the

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.


   The SEARCH method is used to initiate a server-side search.  Unlike
   the HTTP GET method, which requests that a server return a
   representation of the resource identified by the effective request target URI (as
   defined by [RFC7230]), Section 7.1 of [RFCHTTP]), the SEARCH method is used to
   ask the server to perform a query operation (described by the request
   payload) over some set of data scoped to the effective request URI.
   The payload returned in response to a SEARCH cannot be assumed to be
   a representation of the resource identified by the effective request

   The body payload of the request defines the query.  Implementations
   MAY use a request body of any content type with the SEARCH method;
   however, for backwards compatibility with existing WebDAV
   implementations, SEARCH requests that use the text/xml or
   application/xml content media types with a root element (Section 2.1 of
   [XML]) in the "DAV:" XML namespace ([XMLNS]) MUST be processed per
   the requirements established by [RFC5323].
   // This can be relaxed to XML with a document element in the "DAV:"
   // namespace, or even to the two element names mentionbed in
   // Section 2.2.2 of [RFC5323].

   SEARCH requests are both safe and idempotent with regards to the
   resource identified by the request URI.  That is, SEARCH requests do
   not alter the state of the targeted resource.  However, while
   processing a search request, a server can be expected to allocate
   computing and memory resources or even create additional HTTP
   resources through which the response can be retrieved.

   A successful response to a SEARCH request is expected to provide some
   indication as to the final disposition of the search operation.  For
   instance, a successful search that yields no results can be
   represented by a 204 No Content response.  If the response includes a
   body payload, the payload
   content, it is expected to describe the results of the search
   operation.  In some cases, the server may choose to respond
   indirectly to the SEARCH request by returning a 3xx Redirection with
   a Location header field specifying an alternate Request URI from
   which the search results can be retrieved using an HTTP GET request.
   Various non-normative examples of successful SEARCH responses are
   illustrated in Section 4.

   The response to a SEARCH request is not cacheable.  It ought to be
   noted, however, that because SEARCH requests are safe and idempotent,
   responses to a SEARCH MUST NOT invalidate previously cached responses
   to other requests directed at the same effective request URI.
   // By default, that is.  We need to figure out under which conditions
   // we can make the result cacheable.

   The semantics of the SEARCH method change to a "conditional SEARCH"
   if the request message includes an If-Modified-Since, If-Unmodified-
   Since, If-Match, If-None-Match, or If-Range header field ([RFC7232]). ([RFCHTTP],
   Section 13).  A conditional SEARCH requests that the query be
   performed only under the circumstances described by the conditional
   header field(s).  It is important to note, however, that such
   conditions are evaluated against the state of the target resource
   itself as opposed to the collected results of the search operation.

3.  The "Accept-Search" Header Field

   The "Accept-Search" response header field MAY be used by a server to
   directly signal support for the SEARCH method while identifying the
   specific query format Content-Type's media types that may be used.

   Accept-Search = "Accept-Search" ":" 1#media-type

   The Accept-Search header field specifies a comma-separated listing of
   media types (with optional parameters) as defined by [RFC7231], Section 8.3.1 of

   The order of types listed by the Accept-Search header field is

4.  Examples

   The non-normative examples in this section make use of a simple,
   hypothetical plain-text based query syntax based on SQL with results
   returned as comma-separated values.  This is done for illustration
   purposes only.  Implementations are free to use any format they wish
   on both the request and response.

4.1.  Simple SEARCH with a Direct Response

   A simple query with a direct response:

   SEARCH /contacts HTTP/1.1
   Content-Type: text/query example/query
   Accept: text/csv

   select surname, givenname, email limit 10


   HTTP/1.1 200 OK
   Content-Type: text/csv

   surname, givenname, email
   Smith, John,
   Jones, Sally,
   Dubois, Camille,

4.2.  Simple SEARCH with indirect response (303 See Other)

   A simple query with an Indirect Response (303 See Other):

   SEARCH /contacts HTTP/1.1
   Content-Type: text/query example/query
   Accept: text/csv

   select surname, givenname, email limit 10


   HTTP/1.1 303 See Other
   Fetch Query Response:

   GET /contacts/query123 HTTP/1.1


   HTTP/1.1 200 OK
   Content-Type: text/csv

   surname, givenname, email
   Smith, John,
   Jones, Sally,
   Dubois, Camille,

5.  Security Considerations

   The SEARCH method is subject to the same general security
   considerations as all HTTP methods as described in [RFC7231]. [RFCHTTP].

6.  IANA Considerations

   IANA is requested to update the registration of the SEARCH method in
   the permanent registry at <
   methods> (see Section 8.1 16.1.1 of [RFC7231]). [RFCHTTP]).

            | Method Name | Safe | Idempotent | Specification |
            | SEARCH      | Yes  | Yes        | Section 2     |

                                  Table 1

7.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC5323]  Reschke, J., Ed., Reddy, S., Davis, J., and A. Babich,
              "Web Distributed Authoring and Versioning (WebDAV)
              SEARCH", RFC 5323, DOI 10.17487/RFC5323, November 2008,

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 7230, 8174, DOI 10.17487/RFC7230, June 2014,

   [RFC7231] 10.17487/RFC8174,
              May 2017, <>.

   [RFCHTTP]  Fielding, R., Ed. Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,

   [RFC7232]  Fielding, "HTTP Semantics", Work in Progress, Internet-Draft,
              draft-ietf-httpbis-semantics-16, 27 May 2021,

   [XML]      Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
              F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
              Edition)", W3C Recommendation REC-xml-20081126, 26
              November 2008,
              <>.  Latest
              version available at

   [XMLNS]    Bray, T., Hollander, D., Layman, A., Tobin, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Conditional Requests", H.
              Thompson, "Namespaces in XML 1.0 (Third Edition)", W3C
              Recommendation REC-xml-names-20091208, 8 December 2009,
              Latest version available at

Appendix A.  Change Log

   This section is to be removed before publishing as an RFC.

   // (see

A.1.  Since draft-ietf-httpbis-safe-method-w-body-00

   *  Use "example/query" media type instead of undefined "text/query"

   *  In Section 3, adjust the grammar to just define the field value

   *  Update to latest HTTP core spec, and adjust terminology
      accordingly (

   *  Reference RFC 7232,
              DOI 10.17487/RFC7232, June 2014,
              <>. 8174 and markup bcp14 terms

   *  Update HTTP reference (

   *  Relax restriction of generic XML media type in request body

Authors' Addresses

   Julian Reschke
   greenbytes GmbH
   Hafenweg 16
   48155 M√ľnster


   Ashok Malhotra


   James M Snell