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Firefox Nightly — English (US)

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Firefox Nightly — English (US)

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154.0a1 Firefox Nightly

Version 154.0a1, first offered to Nightly channel users on June 15, 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.

Starting with Firefox 152, the address bar in Nightly builds autofills the pages you visit most - including specific pages within a site, not just site homepages - based on your browsing habits, and lets you dismiss suggestions you don’t want.
Bug 2032547

Developer Information

Starting with Firefox 152, Nightly builds allow the attr() function to be used in any CSS property. It now also allows to specify how the attribute value is parsed into a CSS value.
Bug 2038939
Starting with Firefox 154, Firefox Nightly now supports the alpha() CSS function. This is a relative color function that can be used to modify just the alpha component of a given color.
Bug 2047437
Starting with Firefox 153, Firefox Nightly now supports the sibling-index() and sibling-count() CSS functions. These functions allow an element to be styled with calculations that use its index among its siblings and its total count of siblings (including itself), respectively. Documentation.
Starting with Firefox 153, Firefox Nightly ships an experimental implementation of the link-parameters property by Tyler Thrailkill.
Bug 2046153

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Firefox Nightly — English (US)

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See what landed recently in Firefox Nightly!

154.0a1 Firefox Nightly

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