[blink-dev] Intent to Prototype: Markup based Client Hints delegation for third-party content

[Ari Chivukula]

Contact emails

ari...@chromium.org, jadek...@chromium.org, mike...@chromium.org

Design Doc

https://docs.google.com/document/d/1U3P9yvaT1NXG_qRmY3Lp6Me7M5kTnd3QrBb1yFUVNNk/edit

Specification

https://wicg.github.io/client-hints-infrastructure/

Summary

To support content negotiation use cases such as differential serving of variable fonts, color vector fonts, responsive images, and other third-party content which requires client information lost by user agent reduction. For example: variable fonts allow significantly less font information to be transferred without loss of functionality, but only works on specific operating systems.

 

Blink component

Blink>Network>ClientHints

 

Motivation

It’s already possible to set a Permissions Policy in the HTTP response header, but for sites without the ability to modify HTTP headers a HTML solution would be ideal. This proposal ships a meta tag which allows delegation of client hints to third-party origins. These tags could be included in code-snippets for embedded third-party content for ease of use.

 

For example, to specify third party requests to `https://foo.bar` must include `sec-ch-width` you could include:

<meta name="accept-ch" content="sec-ch-width=( https://foo.bar )">

 

You may still omit the permission policy and rely on the default allowlist as follows:

<meta name="accept-ch" content="sec-ch-width">

 

Note that this is the equivalent of the following today:

<meta http-equiv="accept-ch" content="sec-ch-width">

TAG review

https://github.com/w3ctag/design-reviews/issues/702

Compatibility

We do not anticipate compatibility risks for this addition - Blink currently implements first party client hints via a `http-equiv` meta tag, and that functionality will not be removed or modified.

 

Interoperability

 

Gecko: Neutral

 

WebKit: Requested

 

Web developers: Positive interest from Cloudinary

Debuggability

Any improperly formatted client hint meta tags will be flagged in the Issues tab.

Is this feature fully tested by web-platform-tests?

https://github.com/web-platform-tests/wpt/pull/32142

Tracking bug

https://crbug.com/1219359

Link to entry on the Chrome Platform Status

https://www.chromestatus.com/feature/5684289032159232

[Ari Chivukula]

Please ignore this thread and use https://groups.google.com/a/chromium.org/g/blink-dev/c/JQ68cvYuiQU instead. This one was mislabeled as an intent to prototype, when it should be an intent to ship.