As an intervention we want to limit the rate at which timers in out-of-view, cross-origin frames are able to fire. Until very recently it wasn't possible for script authors to easily determine whether their content was visible to the user or not. A common pattern therefore is to use a continuous setTimeout() loop for driving animations without considering visibility, which can be very costly for performance.

Demo

• http://fiddle.jshell.net/3L9c9uyc/3/show/light/

Documentation

• https://docs.google.com/document/d/1Xa8sd2M_Eh6hGSWeKTy_akzKdxcVZjCk4PQMqV8yXXw/edit
• https://github.com/WICG/interventions/issues/9

Status in Chromium

Blink components: Blink

Browser Intervention (tracking bug) in:

• Chrome for desktop release 57
• Chrome for Android release 57
• Android WebView release 57

Consensus & Standardization

• Firefox: In development
• Edge: Positive
• Safari: Shipped/Shipping
• Web Developers: No signals

Owner

• skyostil@chromium.org

Comments

A potential compatibility risk is that a site can observe timers firing out-of-order if the timers are scheduled from a mix of visible and hidden frames. To reduce this risk, we propose to only throttle timers in cross-origin frames.

Last updated on 2021-01-02