The 'Lang' Client Hint
draft-west-lang-client-hint-00

Document Type Active Internet-Draft (individual)
Last updated 2018-11-29
Stream (None)
Intended RFC status (None)
Formats plain text pdf html bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
HTTP                                                             M. West
Internet-Draft                                                    Google
Intended status: Standards Track                       November 29, 2018
Expires: June 2, 2019

                         The 'Lang' Client Hint
                     draft-west-lang-client-hint-00

Abstract

   This document defines a Client Hint that aims to allow developers to
   opt-in to the ability to perform content negotiation based on the set
   of natural languages preferred by the user agent.  This new mechanism
   is intended to improve upon the privacy properties of the "Accept-
   Language" header, and eventually to supplant it entirely.

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 June 2, 2019.

Copyright Notice

   Copyright (c) 2018 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.

West                      Expires June 2, 2019                  [Page 1]
Internet-Draft           The 'Lang' Client Hint            November 2018

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  The 'Lang' Client Hint  . . . . . . . . . . . . . . . . . . .   3
     2.1.  The 'Sec-CH-Lang' Header Field  . . . . . . . . . . . . .   3
     2.2.  Integration with Fetch  . . . . . . . . . . . . . . . . .   4
   3.  Security and Privacy Considerations . . . . . . . . . . . . .   4
     3.1.  Secure Transport  . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Delegation  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  Access Restrictions . . . . . . . . . . . . . . . . . . .   5
   4.  Implementation Considerations . . . . . . . . . . . . . . . .   5
     4.1.  The 'Accept-Language' Header  . . . . . . . . . . . . . .   5
     4.2.  The 'Sec-CH-' prefix  . . . . . . . . . . . . . . . . . .   6
     4.3.  What about weight?  . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  'Sec-CH-Lang' Header Field  . . . . . . . . . . . . . . .   6
     5.2.  'Accept-Language' Header Field  . . . . . . . . . . . . .   7
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Appendix A.  Changes  . . . . . . . . . . . . . . . . . . . . . .   8
     A.1.  draft-west-ua-client-hints-00 . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Today, user agents generally specify a set of preferred languages as
   part of each HTTP request by sending the "Accept-Languages" header
   along with each request (defined in Section 5.3.5 of [RFC7231]).
   This header aims to give servers the opportunity to serve users the
   best content available in a language they understand.  For example,
   my browser currently sends the following header:

     Accept-Language: en-US, en;q=0.9, de;q=0.8

   This tells the server something along the lines of "This user prefers
   American English, but will accept any English at all.  If no English-
   languge content is available, try German!".  If the server has
   English-language content, it might redirect the user agent to that
   preferred content.  If not, it might try German.

   In the best case, this kind of content negotiation sincerely improves
   the user experience, giving them legible content they enjoy reading.
   This comes with a cost, however, as language preferences are fairly
   unique, and end up exposing quite a bit of entropy to the web.

   This document proposes a mechanism that might allow user agents to
   reduce the passive fingerprinting surface exposed by the "Accept-
Show full document text