Firefox 121 is out with AV1 improvements, new features for PDF viewer, and more

Firefox logo with number 121 behind it

Mozilla Foundation has released the final feature update for its browser in the Release channel. Version 121 is rolling out to all users, bringing improved AV1 decode on Windows, Voice Control support on macOS, and the Wayland compositor on Linux for better touchpad and touchscreen gestures, improved graphics performance, and more.

What is new in Firefox 121?

Here are the new features mentioned in the release notes for Firefox 121:

Firefox now prompts Windows users to install the Microsoft AV1 Video Extension to enable hardware decoding support for the AV1 video codec from about:support if not already installed.

Firefox now supports Voice Control commands on macOS systems.

On Linux, Firefox now defaults to the Wayland compositor when available instead of XWayland. This brings support for touchpad & touchscreen gestures, swipe-to-nav, per-monitor DPI settings, better graphics performance, and more.

Note that due to Wayland protocol limitations, Picture-in-Picture windows require an extra user interaction (generally right-click on the window) or a shell / desktop-environment tweak. See bug 1621261 for related discussion and tracking, this post for a KDE configuration, and this extension for GNOME.

Firefox can now force links to always be underlined. This option can be enabled in the Browsing section of the Firefox Settings menu.

The PDF viewer now includes a floating button to simplify deleting drawings, text, and images added in PDFs.

Web Platform changes:

The :has() selector is now supported. This allows authors to match an element that has, or "anchors", at least one element matching its relative selector.

The hanging and each-line keywords are now supported for the text-indent CSS property, offering more convenient paragraph layout options for styles such as bibliographies, poetry, etc.

The balance keyword is now supported for the text-wrap CSS property, which can improve the appearance of short multi-line text blocks such as long headings or captions by harmonizing the line lengths.

Lazy loading iframes are now supported

Support has been added for tail call elimination in WebAssembly language to improve support for functional languages.

In addition, Firefox 121 fixes 18 security vulnerabilities to make your browsing more secure. You can find the complete list of security patches here. Developer information is available here, and Firefox for Enterprise 121 release notes here.

Firefox 121 is available on Windows, macOS, and Linux. Head to the official website to download the latest Firefox update. Existing installations will get to version 121 automatically.