Firefox 147 officially released, officially supports XDG base directories after 21 years of bug fixes

The official version of the web browser 'Firefox 147' has been released. The Linux version now supports XDG Base Directory , and the video player now displays in picture-in-picture mode when you move to another tab while a video is playing.

Firefox 147.0, See All New Features, Updates and Fixes
https://www.firefox.com/en-US/firefox/147.0/releasenotes/

◆XDG Base Directory is now officially supported on Linux
The XDG Base Directory , a specification from the freedesktop.org project proposing common standards for Unix-based desktop environments, has finally been officially implemented after 21 years of revisions since its proposal in September 2004. Until now, all configuration files, caches, and other data files were stored under the '.mozilla' directory in the home directory, but from now on, on new installations, they will be placed in '.config', '.local/share', and other directories.

◆ Automatic picture-in-picture function is enabled when the currently playing video goes into the background
When you switch to another tab while a video is playing, the video player will now be displayed in Picture-in-Picture mode. To set this up, go to your browser's settings, go to 'Browsing,' and check 'Keep video playback in Picture-in-Picture mode even when switching tabs.'

Switching to another tab while a video is playing...

The video player will appear in the foreground as a picture-in-picture so you can continue watching the video.

◆Reorganization of tab group items
The 'Tab Group' settings have been reorganized into three categories: 'How to open,' 'Operation,' and 'How to close.'

◆Adding a profile section
You can now manage passwords, bookmarks, and more for each profile. To set this up, go to the browser's general settings and click 'Settings.'

You can create a new profile by clicking 'Manage Profiles'.

◆ 'ToDo list and timer' added to experimental features
Firefox Labs has added 'To-Do List and Timer on Firefox Home.' When enabled, a To-Do List and Timer widget will appear on your home screen.

◆Others
Support for zero-copy hardware decoded video on AMD GPUs, improving video playback performance by eliminating data copies between CPU and GPU memory.
- Support for Safe Browsing V5 protocol
WebGPU support on all Apple Silicon Macs
- Local network access restrictions will be enabled by default for users with 'Enhanced Tracking Protection (ETP) set to strict.'

◆ Correction
- Fixed a bug when dragging draggable buttons
Fixed a bug that caused HTTP/3 requests containing non - UTF-8 header values to time out or fall back to HTTP/2.
- Fixed an issue where some users were unable to select tabs when Firefox was maximized on Windows.
- Linux GNOME Mutter : Fixed window and rendering area sizes to fit the actual pixel grid.

◆ Change
- Changed the Accept-Language header to use the same quality value (q value) as other major browsers.

◆Developers and Web-related
- Display pseudo elements for view transitions in the Elements panel and related animations in the Animations panel
- Elements with a valid anchor-name attribute will display an 'Anchor' badge in the element list view.
- Added a button to the JSON viewer that allows you to import resources into the Firefox Profiler and view the size of each item.
- Pseudo-element selectors can now be added and edited within the CSS Rules panel
・Navigation API support
- Added support for Unicode 17 and new locales
Support for ES modules in service workers
・Support for CSS modules in JavaScript modules
CSS : The counter-* and quotes properties are now available on the ::marker pseudo-element.
・CSS: Introducing anchor positioning
CSS : Implemented rcap, rch, rex, and ric as relative length units based on the root font.
Supports Brotli format compression and decompression in CompressionStream and DecompressionStream
Supports the :active-view-transition-type selector and type-specific view transition API .
・Supports Storage-Access-Headers

Firefox 147 also includes 16 security bug fixes .

The next major version, Firefox 148, is scheduled to be released on Tuesday, February 24, 2026 local time.