Firefox on Linux: The Open Source Browser on an Open Source System

Firefox is the browser of choice for most Linux users who care about FOSS principles. Here's why, and what makes the Firefox ecosystem different from a free software perspective.

Mozilla's Open Source Status

Firefox is genuinely open source. The source code is available at hg.mozilla.org and on GitHub (mirror). The license is MPL 2.0 (Mozilla Public License), which is a weak copyleft license compatible with GPL.

Key repos:

• mozilla-central — main Firefox source
• mozilla-mobile — Firefox for Android (Fenix)
• extensions — major extensions like Multi-Account Containers

Builds: you can compile Firefox from source. The build system uses Python and Rust. Instructions at firefox-source-docs.mozilla.org.

The Manifest Version 3 Situation

Chrome (and Chromium-based browsers) implemented Manifest V3, which fundamentally limits extension network request blocking capabilities. This affects ad blockers like uBlock Origin — on Chrome/Chromium, blocking is less powerful.

Firefox maintains Manifest V2 support and has stated they will continue to support it. Firefox's extension API allows full content script blocking that MV3 restricts.

This matters for FOSS users: uBlock Origin on Firefox is the same powerful tool it's been for years. On Chrome, it's been progressively weakened.

Extensions With Open Source Implementations

Firefox runs open source extensions effectively. Notable ones:

• uBlock Origin — GPLv3, community maintained
• Multi-Account Containers — MPL 2.0, by Mozilla
• NightOwl — dark mode via CSS, minimal footprint, open source
• Tab Manager & Session Saver — open source, all data local JSON
• Bitwarden — AGPL-3.0, self-hostable

Extensions on AMO (Firefox's add-on store) require unobfuscated source code review. This is different from Chrome Web Store where obfuscated extensions are allowed.

LibreWolf: The Hardened Fork

For users who want Firefox without telemetry, LibreWolf is a community-maintained fork that:

• Removes Mozilla telemetry entirely
• Ships with uBlock Origin installed
• Applies privacy-hardening about:config settings
• Available via Flatpak and some distro package managers

Source: codeberg.org/librewolf

LibreWolf is the more FOSS-principled choice if you want to avoid any proprietary data collection in your browser.

Firefox on Linux

Firefox ships in most major distros:

• Debian/Ubuntu: apt install firefox (snap or deb depending on distro version)
• Fedora: installed by default
• Arch: pacman -S firefox (AUR also has firefox-developer-edition, firefox-nightly)
• Gentoo: emerge firefox-bin or compile from source

Wayland support: Firefox has full Wayland support (MOZ_ENABLE_WAYLAND=1 or configure in about:config). Native Wayland rendering is faster and more battery-efficient on modern hardware.

Hardware acceleration: On Linux, GPU acceleration requires setup. About:config → gfx.webrender.all = true + check about:support for compositor. VA-API for video decode needs media.ffmpeg.vaapi.enabled = true.

DNS and Privacy Setup

For FOSS-minded Linux users, the full privacy stack:

1. Firefox with Strict ETP — browser-level tracking protection
2. DoH to NextDNS or self-hosted Pi-hole — DNS-level blocking
3. uBlock Origin in Medium Mode — extension-level script blocking
4. Wireguard VPN — network-level IP routing

Alternatively, use a self-hosted DNS resolver (Unbound) and point Firefox's DoH at your local resolver.

Session Management for Linux Workflows

Linux users often have complex multitasking setups — multiple projects, terminal sessions, research tabs. Tab Manager & Session Saver saves named tab snapshots that complement your workflow.

Sessions are stored as local JSON in Firefox extension storage — the format is human-readable and can be backed up alongside your dotfiles. The extension itself stores no data outside of the local browser.

The Case for Firefox on FOSS Systems

If you're running a FOSS Linux system and care about the browser's impact on your privacy and your software freedom:

1. Firefox is fully open source with source-available code
2. Its extension API (MV2) is more powerful for blocking than Chromium's MV3
3. The extension ecosystem requires code review and prohibits obfuscation on AMO
4. LibreWolf provides a no-telemetry fork if you want that
5. Tor Browser (also Firefox-based) exists if you need stronger anonymity

Chrome and Chromium are the dominant alternatives. Chromium is open source but Google controls the development direction. Brave is Chromium-based. Only Firefox maintains a genuinely independent browser engine (Gecko/SpiderMonkey) as a FOSS project.