The first major release of Firefox in 2026 is out, kicking off a potentially pivotal year for the FOSS browser as Mozilla ‘rewires’ to AI.

Firefox 147.0 brings modest improvements, including a couple of notable buffs for Linux systems, but the majority of changes focus on the foundational upkeep rather than any flashy frontend changes. As such there isn’t much new to see – or screenshot ;).

Still, for a closer look at what’s landing in this update, read on.

Firefox 147: Highlights

Linux Changes

Firefox 147 resolves a 20-year old Linux ‘bug’ by adding support for the Freedesktop.org XDG Base Directory Specification. Better late than never, right?

This change means Firefox will now puts its files in the same locations other Linux apps put theirs: config files files in ~/.config/mozilla, data in ~/.local/share/mozilla and cache in ~/.cache/mozilla, rather than dumping it all in~/.mozilla.

However, this change will not affect existing installations; only fresh installs or new profiles use the new structure. But the benefit in putting things where they should be is a tidier, predicable system structure that makes backups easier.

There’s another Linux ‘fix’ too, although only for users on GNOME and Mutter.

Firefox now updates window and rendering surface sizes to match the actual pixel grid. This will deliver sharper rendering on GNOME on displays where fractional scaling is active, irrespective of Firefox’s actual window size.

Auto-PiP Option Goes Stable

A former Firefox Labs feature goes stable: you can now have videos in web pages automatically open in Picture-in-Picture (PiP) mode when you switch away from the tab.

To enable auto-pip behaviour head to Settings > Browsing and tick the box next to the “Keep playing videos in Picture-in-Picture when switching tabs” setting. If this behaviour gets annoying, untick the box to revert to the standard behaviour.

Performance, Compatibility & Security

Users with AMD GPUs may notice an uptick in video playback performance, as Firefox 147 enables zero-copy playback for hardware-decoded video (where supported). This, Mozilla say, delivers “parity with Intel and NVIDIA GPUs”.

Firefox 147 introduces support for Compression Dictionaries, which could lead to faster web page loading times in low-bandwidth situations. Mozilla say the standard is used by “several major sites and can significantly reduce the number of bytes transferred to load a page.”

Firefox is not just a smidgen faster at web browsing, but also a smidgen safer whilst doing it.

The browser has adopted the Safe Browsing V5 protocol and is migrating away from V4 of the spec. If you use Enhanced Tracking Protection (ETP) on Strict, Firefox enables local network access restrictions so will ask you to allow public websites to use local network resources.

Firefox now handles language preferences the same way as other browsers.

Before, Firefox sent lower priority values (q=0.5) for secondary languages, which caused some servers to ‘incorrectly’ reject requests. Now the browser sends the same priority values as Chrome and co (q=0.9) these compatibility issues are fixed.

Other changes in Firefox 147:

  • WebGPU enabled for Apple Silicon on supported macOS versions
  • Navigation API support to “initiate, intercept, and manage” navigation actions
  • ES modules in service workers, improving compatibility for modern web apps
  • De/CompressionStream now support the Brotli format

Web-dev related changes of note:

  • Support for CSS Module Scripts
  • ::marker pseudo-element supports counter-* + quotes
  • CSS root-font-relative units rcap, rch, rex and ric
  • CSS anchor positioning added for element tethering

Plenty more besides what’s listed above so check over the official release notes for more detail, and the latest set of security patches are available to read if you want to know what vulnerabilities were plugged in this update.

Experimental features

The new split tabs feature I previewed at the end of 2025? Still experimental. But if you manually enabled it after reading about it, this update improves usability: a new menu in the well of each split tab offers a quick way to close split screen tabs or restore them to individual tabs.

Another experimental feature (planned for the first 147.x point update) is a new way to customise keyboard shortcuts. You can “replace hard-to-type or hard-to-remember hotkeys, eliminate conflicts with other software, and create your preferred set”, per Mozilla.

This feature is experimental (expect bugs, some things to not work) but if you’ve longed to be able to change keyboard shortcuts in Firefox, enable the feature by going to about:keyboard in the address bar.

Download Firefox 147

Firefox 147 will be available to download for Windows, macOS and Linux from the official Firefox website from Tuesday, January 13.

Linux users will be able to install this update from their distribution’s preferred channel. On Ubuntu, that’s the Snap Store and the update is downloaded and applied in the background (look out for a prompt to relaunch the browser, if open).

On Linux Mint? You will be able to update to the latest Firefox release through the Mint Update tool, as the distro packages the browser as a traditional .deb package.

If you need to install Firefox on Linux you have plenty of choices: the Firefox Snap or Firefox Flatpak on Flathub, adding the Mozilla APT repo, or the distro-agnostic Linux binary you can grab from the Firefox website or Mozilla FTP.