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Firefox Nightly
Release Notes

Release Notes tell you what’s new in Firefox. As always, we welcome your feedback. You can also file a bug in Bugzilla or see the system requirements of this release.

100.0a1 Firefox Nightly

March 8, 2022

Version 100.0a1, first offered to Nightly channel users on March 8, 2022

Firefox Nightly gets updated every day and as a consequence, the release notes for the Nightly channel are updated continuously to reflect features that have reached sufficient maturity to benefit from community feedback and bug reports.

Warning: Features listed here may or may not make a final release of Firefox.

In addition to these release notes, you can follow ongoing development on our @FirefoxNightly Twitter account as well as read our Nightly Blog.


  • We now support captions/subtitles display on YouTube, Prime Video, and Netflix videos you watch in Picture-in-Picture. Just turn on the subtitles on the in-page video player, and they will appear in PiP.

    Bug 1751505
  • Picture-in-Picture now also supports video captions on websites that use WebVTT (Web Video Text Track) format, like, Canadian Broadcasting Corporation, and many more.

  • Spellchecker now allows multiple language dictionaries at the same time.

    Bug 1402822
  • Hardware accelerated AV1 video decoding was enabled on Windows with supported GPUs (Intel Gen 11+, AMD RDNA 2 Excluding Navi 24, GeForce 30).

    Bug 1652945
  • Scrollbars on Linux and Windows 11 won't take space by default. On Linux, users can change this on about:preferences. On Windows, we follow the system setting (System Settings > Accessibility > Visual Effects > Always show scrollbars). To change this just on Firefox, use the pref from about:config.

    Bug 1757647
  • Firefox now supports credit card autofill and capture in the United Kingdom.

    Bug 1762649


  • Users can now choose the preferred color scheme for websites. Theme authors can now make better decisions about which color scheme Firefox uses for menus etc. Web content appearance can now be changed in about:preferences.


    Bug 1736218
  • Beginning in this release, the Firefox installer for Windows is signed with a SHA-256 digest, rather than SHA-1. Update KB4474419 is required for successful installation on a computer running the Microsoft Windows 7 operating system. For more details about this update, visit the Microsoft Technical Support website.


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