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Firefox Release

March 19, 2019

Version 66.0, first offered to Release channel users on March 19, 2019

We'd like to extend a special thank you to all of the new Mozillians who contributed to this release of Firefox!



  • The Dark and Light Firefox themes now override the system setting for title bar accent color on Windows 10

  • Linux users: Resolved an issue that caused Firefox to freeze when downloading files

  • Various security fixes


  • System title bar is hidden by default to match Gnome guideline for Linux users


  • DevTools Inspector is now fully usable when the Debugger is paused

  • Lowered priority of setTimeout and setInterval during page load to improve overall page load performance

  • Fixed: <button> element is no longer special cased in event dispatch, per latest specifications

Developer Information