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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.

128.0a1 Firefox Nightly

May 13, 2024

Version 128.0a1, first offered to Nightly channel users on May 13, 2024

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


  • Starting with Firefox 127, we're enabling a new anti-tracking feature in Nightly: Bounce Tracking Protection. This protection detects bounce trackers based on redirect behavior and periodically purges their cookies & site data to prevent tracking.

    Bug 1895222
  • Starting with Firefox for Android 128, the new tab strip feature for tablets is available for testing in Nightly builds! This enhancement makes tab management more intuitive and efficient, providing a smoother browsing experience for devices in that form factor. Please share your feedback on Google Play and/or the Mozilla Connect post to help us improve it further.

    Bug 1896355
  • Firefox now supports playback of protected content from streaming sites like Netflix while in Private Browsing mode.

    Bug 1706121
  • Firefox now has a simpler and more unified dialog for clearing user data. In addition to streamlining data categories, the new dialog also provides insights into the site data size corresponding to the selected time range.
    Screenshot of new Clear History dialog

    Bug 1896949
  • Microphone capture through getUserMedia on macOS will use system-provided voice processing when applicable for improved audio quality.

    Bug 1404972
  • Firefox is now available in the Saraiki (skr) language.

    Bug 1900150
  • Starting with Firefox 128, hovering the mouse over an unfocused tab will now display a visual preview of its contents in Nightly builds.

    Bug 1893676
  • Firefox for Android users on Android 14 or later can now create and use Passkeys in third-party Passkey management applications.

    Bug 1862132


  • Firefox now proxies DNS by default when using SOCKS v5, avoiding leaking DNS queries to the network when using SOCKS v5 proxies.

    Bug 1741375


  • Firefox now supports rendering more text/* file types inline, rather than requiring them to be downloaded to be viewed.

    Bug 196078

Web Platform

  • Starting with Firefox 125, the transition-behavior CSS property is now supported in Nightly builds.

    Bug 1805727
  • Starting with Firefox 125, Nightly builds will attempt to establish TLS connections using a hybrid post-quantum key agreement mechanism (X25519+Kyber768). This may result in slow TLS handshakes or failed connections on networks with TLS intercepting middleboxes. The feature can be disabled by setting the security.tls.enable_kyber preference to false.

    Bug 1878725
  • Starting with Firefox 126, the shape() function on clip-path property is now supported in nightly builds.

    Bug 1823463
  • Starting with Firefox 126, the shape() function on offset-path property is supported in nightly builds.

    Bug 1884424
  • Starting with Firefox 126, interpolation between path() function and shape() function is now supported in nightly builds.

    Bug 1884425
  • Starting with Firefox 127, Nightly users now have the ability to translate selections of text from the right-click context menu, rather than only being able to translate the entire web page.

    Bug 1890299
  • Starting with Firefox 127, the relative color syntax is supported in CSS color functions in Nightly builds. This allows to create colors based on other colors.

    Bug 1893965
  • Starting with Firefox 127, @starting-style is supported in Nightly builds. This at-rule allows to define styles that are applied to an element when it is first rendered, enabling transitions on elements that are added to the DOM or that have their display type changed from none to another value.

    Bug 1834876
  • The setCodecPreferences method allows applications to disable the negotiation of specific codecs (including RTX/RED/FEC). It also allows an application to cause a remote peer to prefer the codec that appears first in the list for sending.

    Bug 1396922
  • The Accept header for images and documents was changed to better align with the Fetch standard and other browsers.

    Bug 1711622
  • Firefox now supports @property and the CSS properties-and-values API.

    Bug 1864818
  • Starting with Firefox 128, Firefox Nightly now has initial support for the CHIPS (Cookies Having Independent Partitioned State) standard.

    Bug 1898253
  • Resizeable ArrayBuffers and Growable SharedArrayBuffers are now supported in SpiderMonkey. This allows the size of an ArrayBuffer to be changed without having to allocate a new buffer and copy data into it.

    Bug 1884150

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