HTTP Client Hints
draft-ietf-httpbis-client-hints-04
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2017-04-18
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draft-grigorik-http-client-hints
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Experimental
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"Mark Nottingham" <mnot@mnot.net>
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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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