Identify cases where a user touch scroll is likely to be blocked on the main thread for a long time, and force the touch events to be uncancellable, allowing the scroll to occur on the compositor without blocking on main. This will replace the existing Touch Ack Timeout.


Status in Chromium


In developer trial (Behind a flag) (tracking bug)

Consensus & Standardization

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

  • No signal
  • No signal
  • No signals



Other browsers don't implement this precise intervention, but we do see interventions meant to address the same issue. Safari: Safari has some odd behavior around touch event handlers cancellability when the main thread is busy, but it isn’t consistent. Edge: Edge appears to have something equivalent to the Touch Ack Timeout (verified experimentally on Firefox: The "APZ content response timeout" is equivalent to our Touch Ack Timeout.

Last updated on 2021-12-05