Download Firefox

Firefox is no longer supported on Windows 8.1 and below.

Please download Firefox ESR (Extended Support Release) to use Firefox.

Firefox is no longer supported on macOS 10.14 and below.

Please download Firefox ESR (Extended Support Release) to use Firefox.

Firefox Privacy Notice

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.

120.0a1 Firefox Nightly

September 25, 2023

Version 120.0a1, first offered to Nightly channel users on September 25, 2023

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, our Mastodon account as well as read our Nightly Blog.

You can interact with other Firefox Nightly users and give your feedback to Mozilla staff in the Nightly Matrix room on


  • Keyboard shortcuts have now been added for editing and deleting a selected credential on about:logins. For editing - Alt + enter (Option + return on macOS) and for deleting - Alt + Backspace (Option + Delete on macOS).

    Bug 1845583
  • Users on Ubuntu Linux now have the ability to import from Chromium when both are installed as Snap packages.

    Bug 1818237
  • Users can now use an added devtools feature to simulate browser tabs to be offline.

    Bug 1156659
  • Picture-in-Picture now supports corner snapping on Windows and Linux - just hold Ctrl as you move the PiP window.

    Bug 1772404
  • Firefox now imports TLS trust anchors (e.g., certificates) from the operating system root store. This will be enabled by default on Windows, macOS, and Android, and if needed, can be turned off in settings (Preferences → Privacy & Security → Certificates).

    Bug 1848815
  • Firefox now supports a setting (in Preferences → Privacy & Security) to enable Global Privacy Control. With this opt-in feature, Firefox informs the websites that the user doesn’t want their data to be shared or sold.

    UI setting for GPC

    Bug 1830623


  • The User Activation API has now been added, allowing JavaScript to check if the user currently is or has been active with the page (clicking, etc) with navigator.userActivation.

    Bug 1791079
  • Early Hints Preconnect, the informational status code 103, is now enabled. This allows servers to send resource Link headers before the final HTTP response and improves performance on servers using this feature. (read more)

    Bug 1858712
  • Starting with Firefox 120, Lazy loading iframes are now supported (<iframe loading=lazy>) for nightly users. Lazy loading iframes are only loaded when visible, so non-critical iframes can load later when needed to speed up initial page loads, reduce initial network usage, etc.

    Bug 1860057

Web Platform

  • lh and rlh units can now be parsed and computed correctly as lengths. This allows authors to specify lengths in terms of the element's (or the root element's) line height.

    Bug 1310170
  • WebAssembly GC is now enabled by default, which allows new languages, such as Dart or Kotlin, to run on Firefox. This makes it possible for reference cycles between the guest language and host browser to be collected.

    Bug 1845373
  • Starting with Firefox 117, partial support for the custom highlight API is now available in Nightly builds, allowing web developers to give ranges an appearance.

    Bug 1840818
  • Starting with Firefox 119, the :has() selector is now available in nightly builds. This allows authors to match elements that has, or "anchors", at least one element matching its relative selector.

    Bug 1853701
  • Starting with Firefox 120, ULPFE/RED is now on by default for video in Nightly builds. This provides additional protection against packet loss for video during WebRTC calls.

    Bug 1852837

Get the most recent version

All Firefox Nightly downloads