How we built it

Stylesheets activated after the body is started do not block paint

External stylesheets in the body of the document or that get activated after the body has started to be parsed will no longer block paint. The parser will still block at a script tag until all prior stylesheets have loaded, including those in the body.


This is the existing Firefox behavior. Edge is similar but also blocks the parser so that content after the external sheet is not displayed until after the stylesheet loads. The Edge behavior can be mimicked in Firefox (and blink with this change) by placing an empty script tag after the relevant sheets which will cause the parser to block. Safari has the current blink behavior where all external stylesheets will disable all painting until they have loaded.


Status in Chromium

Behind a flag (launch bug) in:

  • Chrome for desktop release 52
  • Chrome for Android release 52
  • Chrome for iOS release 52
  • Android WebView release 52
  • Opera release 39
  • Opera for Android release 39

Consensus & Standardization

  • Shipped
  • No public signals
  • No public signals
  • Strongly positive


Last updated on 2016-07-28