Intervention: WebFonts use adaptive timeouts to take fallback fonts

Originally, Blink use fallback fonts if the font loading isn't finished in 3 seconds. But this timeout value wasn't defined in any spec. Blink changes this timeout adaptively to improve performance on slow connections. If font-display feature is enabled, this change happens only if 'auto' is specified to follow the font-display spec. Otherwise, it happens always. The definition of slow connection would be changed in the field trial.

Comments

Chrome 49, the feature is enabled as a User-Agent Intervention. 2G Cellular connection will trigger the intervention. Chrome 53, network quality estimator has been used to trigger the intervention on effectively slow networks. This estimator-based intervention was enabled by default in Chrome 59. Developer tools shows a warning message when the intervention is triggered for each font. Web site owners can opt-out from the intervention by setting CSS font-display to other than 'auto'.

Documentation

Specification

Editor's draft

Status in Chromium

Blink>Fonts


Enabled by default (tracking bug) in:

  • Chrome for desktop release 49
  • Chrome for Android release 49
  • Chrome for iOS release 49
  • Opera release 36
  • Opera for Android release 36

Consensus & Standardization

After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.

  • No public signals
  • No public signals
  • No public signals
  • No signals

Owners

Last updated on 2017-12-07