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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.

151.0a1 Firefox Nightly

March 23, 2026

Version 151.0a1, first offered to Nightly channel users on March 23, 2026

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 Bluesky account, our @FirefoxNightly 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 chat.mozilla.org.

New

  • Starting with Firefox 149, Nightly builds now ship with a new .rpm package for Linux users on Red Hat, Fedora, openSUSE, and other RPM-based distributions.

    Bug 213920

  • Starting with Firefox 149, Nightly builds now support throttling for Web Workers running in inactive tabs. When a tab becomes inactive, Firefox reduces how aggressively its workers can run timeouts.

    Bug 2011100

  • Starting with Firefox for Android 150, Nightly users can now choose a custom default location for their downloads.

    Bug 2019009

Developer

Web Platform

  • Starting with Firefox 149, you can now set specific color spaces and transparency (alpha) on <input type="color"> elements, with alpha support currently exclusive to Firefox Nightly. While the visual picker hasn't changed yet (tracked in Bug 2007532), it will now output values in your requested format.

    Bug 1919718

  • Starting with Firefox 150, multiple import maps per document are now supported in Nightly builds, giving web developers more flexibility when structuring and loading modern JavaScript modules. This is considered experimental as we gather feedback before enabling it in regular releases.

    Bug 1916277

    This feature is part of a progressive roll out.

    What is a progressive roll out?

    Certain new Firefox features are released gradually. This means some users will see the feature before everyone does. This approach helps to get early feedback to catch bugs and improve behavior quickly, meaning more Firefox users overall have a better experience.

  • Starting with Firefox 150, the rendering of absolutely positioned elements across multi-column containers and in printing is improved in Nightly builds, ensuring a more accurate element positioning and fragmentation.

    Bug 2018797

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