Mozilla has rolled out Firefox 147, the browser’s first major update of 2026. While it won’t dazzle with visual redesigns, it sets the tone for a year focused on deeper architectural changes as Firefox continues adapting to an AI-driven web.
This release leans heavily toward maintenance, compatibility, and platform polish. There are a few user-facing additions—especially for Linux—but most of the work happens beneath the surface.
Here’s what stands out.
What’s New in Firefox 147
Long-Overdue Linux Improvements
After roughly two decades, Firefox finally aligns with the XDG Base Directory Specification on Linux. That means new installs and newly created profiles now store files in standard locations:
- Configuration:
~/.config/mozilla - Application data:
~/.local/share/mozilla - Cache:
~/.cache/mozilla
Previously, everything lived inside ~/.mozilla. Existing profiles won’t be moved automatically, but future installs benefit from a cleaner, more predictable layout that plays better with backups and system maintenance tools.
There’s also a fix specifically for GNOME/Mutter users. Firefox now adjusts its window and rendering surfaces to match the actual pixel grid, improving visual clarity on displays using fractional scaling—regardless of the browser window’s size.
Automatic Picture-in-Picture Becomes Default
A feature previously hidden behind Firefox Labs has graduated to stable: automatic Picture-in-Picture.
When enabled, videos will pop out into PiP mode as soon as you switch away from their tab. You can turn this on (or off) via:
Settings → Browsing → “Keep playing videos in Picture-in-Picture when switching tabs”
It’s a convenience feature that’s easy to try—and just as easy to disable if it feels intrusive.
Performance, Compatibility, and Security Updates
Firefox 147 brings a welcome boost for users with AMD graphics hardware. Zero-copy playback is now enabled for hardware-decoded video where supported, improving efficiency and bringing performance closer to what Intel and NVIDIA users already enjoy.
The browser also adds support for Compression Dictionaries, a web standard that can significantly reduce data transfer on supported sites—particularly useful on slower or constrained connections.
On the security side, Firefox transitions to the Safe Browsing V5 protocol. Users running Enhanced Tracking Protection in Strict mode may now see prompts when websites attempt to access local network resources, adding another layer of control.
Language handling has also been adjusted for better web compatibility. Firefox now sends language preference values that match other major browsers, avoiding issues where servers previously rejected requests due to Firefox’s lower priority weighting.
Additional Noteworthy Changes
- WebGPU is now enabled on Apple Silicon Macs (where supported)
- Navigation API support expands control over page navigation
- Service workers can now use ES modules
- Brotli support added to DecompressionStream and CompressionStream
For web developers, Firefox 147 includes updates such as:
- CSS Module Scripts support
- Expanded
::markerpseudo-element functionality - New root-relative font units (
rcap,rch,rex,ric) - CSS anchor positioning for more flexible layout anchoring
As always, the official release notes contain a deeper breakdown, along with details on patched security vulnerabilities.
Experimental Features Continue to Evolve
The split tabs feature previewed late last year remains experimental, but it’s improved. Each split view now includes a small menu that lets you quickly close the split or return tabs to their normal layout.
Mozilla is also preparing an experimental keyboard shortcut customization system, expected to arrive in an upcoming 147.x update. This feature allows users to remap shortcuts, resolve conflicts, and tailor Firefox’s key bindings to their preferences.
Adventurous users can enable it now by visiting:
about:keyboard
Just keep in mind: it’s still a work in progress.
Firefox 147 may not shout for attention, but it quietly delivers meaningful refinements—especially for Linux users—while laying groundwork for what’s coming next.
