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.


From Chrome 49, the feature is enabled as a User-Agent Intervention. 2G Cellular connection will trigger the intervention. From Chrome 53, another field trial is enabled and a flag is available to enable the feature explicitly. The new trial trigger the intervention on effectively slow networks. From this release, the feature is enabled on all platforms by default, but threshold would be changed day by day while the trial under a server side configuration.


Editor's draft

Status in Chromium


Enabled by default (launch 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

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


Last updated on 2017-06-14