HTTP Client Hints
draft-ietf-httpbis-client-hints-07

Document Type Active Internet-Draft (httpbis WG)
Last updated 2019-04-28 (latest revision 2019-03-11)
Replaces draft-grigorik-http-client-hints
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Intended RFC status Experimental
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HTTP Working Group                                           I. Grigorik
Internet-Draft                                                    Google
Intended status: Experimental                             March 11, 2019
Expires: September 12, 2019

                           HTTP Client Hints
                   draft-ietf-httpbis-client-hints-07

Abstract

   HTTP defines proactive content negotiation to allow servers to select
   the appropriate response for a given request, based upon the user
   agent's characteristics, as expressed in request headers.  In
   practice, clients are often unwilling to send those request headers,
   because it is not clear whether they will be used, and sending them
   impacts both performance and privacy.

   This document defines two response headers, Accept-CH and Accept-CH-
   Lifetime, that servers can use to advertise their use of request
   headers for proactive content negotiation, along with a set of
   guidelines for the creation of such headers, colloquially known as
   "Client Hints."

   It also defines an initial set of Client Hints.

Note to Readers

   Discussion of this draft takes place on the HTTP working group
   mailing list (ietf-http-wg@w3.org), which is archived at
   https://lists.w3.org/Archives/Public/ietf-http-wg/.

   Working Group information can be found at http://httpwg.github.io/;
   source code and issues list for this draft can be found at
   https://github.com/httpwg/http-extensions/labels/client-hints.

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 https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any

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   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 September 12, 2019.

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
   2.  Client Hint Request Header Fields . . . . . . . . . . . . . .   4
     2.1.  Sending Client Hints  . . . . . . . . . . . . . . . . . .   4
     2.2.  Server Processing of Client Hints . . . . . . . . . . . .   5
       2.2.1.  Advertising Support via Accept-CH Header Field  . . .   5
       2.2.2.  The Accept-CH-Lifetime Header Field . . . . . . . . .   5
       2.2.3.  Interaction with Caches . . . . . . . . . . . . . . .   6
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Accept-CH . . . . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  Accept-CH-Lifetime  . . . . . . . . . . . . . . . . . . .   8
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   9
     5.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Appendix A.  Interaction with Key Response Header Field . . . . .   9
   Appendix B.  Changes  . . . . . . . . . . . . . . . . . . . . . .  10
     B.1.  Since -00 . . . . . . . . . . . . . . . . . . . . . . . .  10
     B.2.  Since -01 . . . . . . . . . . . . . . . . . . . . . . . .  10
     B.3.  Since -02 . . . . . . . . . . . . . . . . . . . . . . . .  10
     B.4.  Since -03 . . . . . . . . . . . . . . . . . . . . . . . .  10
     B.5.  Since -04 . . . . . . . . . . . . . . . . . . . . . . . .  10
     B.6.  Since -05 . . . . . . . . . . . . . . . . . . . . . . . .  10
     B.7.  Since -06 . . . . . . . . . . . . . . . . . . . . . . . .  10
     B.8.  Since -07 . . . . . . . . . . . . . . . . . . . . . . . .  11

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