Firefox fans on Linux will enjoy smaller download sizes and faster decompressing when using the official binary builds from the Mozilla website.
The browser maker today announced its switching to the tar.xz format — yes, that xz —to distribute its Linux builds, which uses the more efficient LZMA compression algorithm to deliver smaller downloads and faster extraction times.
Most Linux users get Firefox updates as a regular software update from a distro-maintained repo, e.g., a Firefox Snap on Ubuntu, a Firefox DEB on Linux Mint and Pop!_OS, etc.
But Mozilla say by switching from BZIP2 (tar,bz2) to XZ (tar.xz) Linux users benefit from faster downloads (packages are on average 25% smaller than before) and faster extraction times (decompression times said to be 2x quicker).
“In our ongoing effort to optimize Firefox for all users, we are transitioning the packaging format of Firefox for Linux from .tar.bz2 to .tar.xz”, Mozilla says.
“This change results in smaller download sizes and faster decompression times, making your experience smoother and more efficient.”
The change may, in time, require any Linux distribution maintainers build tools or scripts which fetch the binary builds to adapt to the change – but that’ll be easy enough; Firefox itself is unaffected, only the archive format it comes in is changing.
Why change, and why now?
Although minor in the grand scheme, a more efficient distribution format for binary builds has been on the cards for a while – as far back as 2020, in fact.
Initially, developers were just exploring optimisations, and some of those who were working on Firefox felt that given distro builds are what the majority of people use, and engineering time could be better spent on other things, there was no need to prioritise a switch.
But, smaller downloads reduces Mozilla’s storage, bandwidth and CDN costs, and helps both developers and users fetching builds frequently – with Mozilla tightening its belt of late, all savings help.
Benchmarks also show that XZ compression (important for Mozilla’s build infrastructure creating the packages) uses less memory and is faster than Bzip2.
Mozilla say it did consider Zstd (aka .tar.zst) but that XZ found to offer the biggest gains overall in both size and decompression.
Download Firefox .tar.xz Packages
To start, only Firefox Nightly for Linux use .tar.xz (you can download those here) but, in time, all Firefox editions – developer, beta, stable, and ESR – will make the switch.
For existing users there’s not really a major impact (if they currently use a binary build it will continue to auto-update without issue).
But for those who regularly download different builds to test/check/debug features/changes, faster downloads is nothing to be sniffed out.