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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.

152.0a1 Firefox Nightly

April 20, 2026

Version 152.0a1, first offered to Nightly channel users on April 20, 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 for Android 150, Nightly users can now choose a custom default location for their downloads.

    Bug 2019009

  • Starting with Firefox 151, Firefox for Android nightly builds include settings for enabling fine-grained control of AI features and also allows you to block future AI features.

    Bug 2029260

  • Starting with Firefox 151, you can merge multiple PDFs within the Firefox PDF viewer in Nightly builds.

    Bug 2030178

Developer

  • Developer Information

  • Starting with Firefox 151, the JavaScript Tracer can be enabled from DevTools Settings panel in Nightly builds. This enables tracing all JavaScript function calls. Unlike the performance profiler, this doesn't record a sample; instead, it traces all function calls.

    Bug 2022844

Web Platform

  • 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.

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