HTTP Client Hints
draft-ietf-httpbis-client-hints-04

Document Type Active Internet-Draft (httpbis WG)
Last updated 2017-04-18
Replaces draft-grigorik-http-client-hints
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HTTP Working Group                                           I. Grigorik
Internet-Draft                                                    Google
Intended status: Experimental                             April 18, 2017
Expires: October 20, 2017

                           HTTP Client Hints
                   draft-ietf-httpbis-client-hints-04

Abstract

   An increasing diversity of Web-connected devices and software
   capabilities has created a need to deliver optimized content for each
   device.

   This specification defines a set of HTTP request header fields,
   colloquially known as Client Hints, to address this.  They are
   intended to be used as input to proactive content negotiation; just
   as the Accept header field allows user agents to indicate what
   formats they prefer, Client Hints allow user agents to indicate
   device and agent specific preferences.

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 http://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
   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 October 20, 2017.

Grigorik                Expires October 20, 2017                [Page 1]
Internet-Draft              HTTP Client Hints                 April 2017

Copyright Notice

   Copyright (c) 2017 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
   (http://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 . . . . . . . . . . . .   4
       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.  Client Hints  . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  The DPR header field  . . . . . . . . . . . . . . . . . .   7
       3.1.1.  Confirming Selected DPR . . . . . . . . . . . . . . .   7
     3.2.  The Width header field  . . . . . . . . . . . . . . . . .   8
     3.3.  The Viewport-Width header field . . . . . . . . . . . . .   8
     3.4.  The Downlink header field . . . . . . . . . . . . . . . .   8
     3.5.  The Save-Data header field  . . . . . . . . . . . . . . .   8
   4.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Accept-CH . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.2.  Accept-CH-Lifetime  . . . . . . . . . . . . . . . . . . .  11
     6.3.  Content-DPR . . . . . . . . . . . . . . . . . . . . . . .  11
     6.4.  Downlink  . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.5.  DPR . . . . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.6.  Save-Data . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.7.  Viewport-Width  . . . . . . . . . . . . . . . . . . . . .  12
     6.8.  Width . . . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
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