User-Agent Client Hints (UA-CH)

[Llbe]

AFAIU, the plan from Google is to freeze the User-Agent header value (with some support from other vendors) and introduce new client hint headers in their place, along with a new JS API that can be used instead of navigator.userAgent in order to target specific browser versions etc.

Intent to Deprecate and Freeze: The User-Agent string: https://groups.google.com/a/chromium.org/forum/m/#!msg/blink-dev/-2JIRNMWJ7s/yHe4tQNLCgAJ

Intent to Ship: Client Hints infrastructure and UA Client Hints: https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/A4wxFpvqUfA/g7iccl9ICgAJ

Spec on JS API: https://wicg.github.io/ua-client-hints/#interface

[kiding]

Google's plan to freeze the User-Agent string has been postponed to "at least 2021." w3ctag/design-reviews#467 (comment)

[adriaandotcom]

Client Hints are implemented in Google Chrome (at least v88):

[pointydev]

• Resources:
  • Chromium Blog: Update on User-Agent String Reduction in Chrome
  • Chromium updates > User-Agent Reduction

• Support:
  • Chromium: Enabled by default in v89 - https://www.chromestatus.com/feature/5995832180473856
  • Edge: Supported since Edge Chromium v89
  • Firefox: Unsupported (tested on Nightly 92.0a1), position originally non-harmful, downgraded to harmful - https://mozilla.github.io/standards-positions/#ua-client-hints
  • Safari: Unsupported
  • IE: Unsupported