Preserve request priorities through service worker

Preserves a request’s original priority when it passes through a service worker. Previously, all requests going through a service worker would get "High" priority. This means render-blocking style sheets would have their priority clamped, while less-important resources would get boosted. The priority of network requests can be seen in the DevTools network tab. Render-blocking resources such as style sheets have "Highest" priority, while resources like async scripts have "Low" priority.


Last year I landed changes ensuring the priorities higher than "High" were preserved through a Service Worker. This chromestatus entry is mostly for tracking the other half of the changes: preserving priorities lower than "High" when they requests pass through a Service Worker.


Editor's draft

Status in Chromium


Enabled by default (tracking bug) in:

  • Chrome for desktop release 77
  • Chrome for Android release 77
  • Android WebView release 77

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


Intent to Implement url

Intent to Implement thread

Last updated on 2019-07-11