See what landed recently in Firefox Nightly!

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.

143.0a1 Firefox Nightly

July 21, 2025

Version 143.0a1, first offered to Nightly channel users on July 21, 2025

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 142, Nightly builds support creating URLs using Text Fragments. You can generate such a URL by selecting a snippet of text on a page and choosing Copy Link to Highlight from the context menu.

    Bug 1970641

Developer

Web Platform

  • Starting with Firefox 140, Nightly builds now support CloseWatcher including integration with popovers and dialogs.

    Bug 1966459

  • Starting with Firefox 142, Nightly builds now support the Integrity-Policy header allowing websites to ensure that all of their scripts are protected with integrity data. It is currently limited to scripts but will be expanded in the future to provide full web application integrity.

    Bug 1976656

Get the most recent version

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