Firefox
Menu

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.

149.0a1 Firefox Nightly

January 12, 2026

Version 149.0a1, first offered to Nightly channel users on January 12, 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

  • Many PDF files will now load significantly faster thanks to hardware acceleration.

    Bug 2006057

  • Firefox now automatically blocks notifications and permanently revokes permissions for any website flagged as malicious by SafeBrowsing. This prevents unsafe sites from sending background notifications to users, commonly used for ads, spam or phishing.

    Bug 2015830

  • You can now add a Share button to your toolbar via Customize Toolbar, making it easy to share the current tab using your Windows or macOS system sharing options.

    Bug 1717290

  • Address Autofill is enabled for users in Australia, India, Italy, Poland and Austria.

    Bug 2013319

  • Starting with Firefox 148, Split View is enabled in Nightly builds. You can view two tabs side-by-side in a single window, making it easier to compare information, research topics, or work across multiple pages at once. You can create a Split View directly from a tab’s context menu.

    Bug 2006193

  • Starting with Firefox 148, Nightly builds have stability improvements to the legacy search bar, as well as aligning its search button with the latest designs.

    Bug 2006632

  • Starting with Firefox 148, the updated Firefox sidebar is now enabled by default for new profiles in Nightly builds. It provides quick access to tools like bookmarks, history, and AI chatbots. Use the settings gear icon at the bottom of the sidebar to add and remove tools, try vertical tabs, or move the sidebar.

    Bug 1978102

  • Starting with Firefox 148, HDR video on Windows is now supported in Nightly builds. This is considered experimental as we gather feedback before enabling it in regular releases. This feature works best when HDR mode is enabled in Display Settings (this may require a page refresh); otherwise, the display driver is likely to apply a tonemapping effect for non-HDR viewing. Some streaming sites may still not offer HDR video in Firefox. (Learn more)

    Bug 1977746

  • 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, in Nightly builds WebGL/WebGPU is rendered as overlay on Windows if supported.

    Bug 2008399

  • The WebRender layer compositor is now enabled on Windows, reducing power usage during full-screen video playback and improving WebGL/WebGPU performance.

    Bug 2000149

  • 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

  • Added an AI Controls section to Settings for managing AI-enhanced features.

    image for AI controls in Settings

    Bug 2011957

Fixed

  • Increased robustness of HTTP/3 upload performance for unstable network conditions.

    Bug 1852924

Changed

  • The TrustPanel combines the privacy and security panels accessed from the address bar to give the user one place to check the Privacy and Security settings of the current page. Learn more.

    TrusPanel Screenshot

    Bug 2008405

  • Starting with Firefox 149, on Windows, Firefox will use the modern Windows.Devices.Geolocation API for geolocation instead of Windows 7 location API.

    Bug 1980653

  • Security has been strengthened by tightening the requirements for JavaScript files that can be loaded in the parent process, providing additional defense in depth against potential threats.

    Bug 2007588

  • On Linux, Firefox will now default to the XDG portal file picker if available, rather than the GTK3 one, which is usually better integrated with the user's desktop environment, and more powerful.

    Bug 1949057

Developer

Web Platform

  • Starting with Firefox 148, Nightly builds now support the Document Picture-in-Picture API, which allows web pages to place content in an always-on-top popup.

    Bug 1858562

  • Starting with Firefox 148, Nightly builds now open an in-page popup for <input type=color> instead of an OS-dependent color picker. Which means it now shows the same behavior on all desktop platforms.

    Bug 1629388

  • 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

  • showPicker() now supports text-based <input> elements with an associated <datalist>, displaying the autofill dropdown. See documentation.

    Bug 1998668

  • The functions xywh() and rect() were previously implemented for the clip-path and offset-path properties. They are now also available for the shape-outside property.

    Bug 1983187

  • The math value of the CSS font-family is now supported and used by default for MathML's <math> element. It enables Web developers to indicate special fonts with advanced math features should be used. Firefox will rely on the serif font for mathematics defined in Firefox preferences.

    Bug 2014703

  • Added support for the HTML attribute popover="hint".

    Bug 1867743

  • Starting with Firefox 149, the spec-compliant HTMLMediaElement.captureStream() API is now enabled in Nightly builds.

    Bug 2016216

  • Enabled media element pseudo-classes, such as :playing, :paused…

    Bug 2013367

  • Enabled the spec-compliant HTMLMediaElement.captureStream() API.

    Bug 2017708

  • Added support for closing popovers & dialogs with the Android Back Button, and implemented the CloseWatcher API for handling this in script.

    Bug 1966073

  • The new Reporting API provides a generic reporting mechanism for web applications to use to make reports available based on various platform features (for example Content Security Policy, Permissions-Policy or feature deprecation reports) in a consistent manner.

    Bug 1976074

Get the most recent version

Need help or want to leave feedback?

File a bug Leave feedback

Get Involved

Did you know that most of the content in Firefox Support was written by volunteers?

Find out more

Other Resources

Firefox Nightly News Developer Information Complete list of changes for this release Press Kit Mozilla and Firefox News Firefox Extended Support Release All Firefox for Desktop Releases Learn more about Firefox