6 Firefox Forks Worth Trying in 2026

Six Firefox forks are actively maintained and worth trying: LibreWolf, Floorp, Zen Browser, Waterfox, Mullvad Browser and Tor Browser. Each one changes different defaults, and they don’t all follow the same Firefox release track.

Mozilla now ships a new Firefox major version every two weeks. If that pace bothers you, or you’re tired of turning off the same settings on every new machine, a fork may suit you better than about:config tweaks.

This article lists each fork’s Firefox base, platforms and main changes. It also covers what these forks mean when you test your own sites.

What Are Firefox Forks and Why Do People Use Them?

A Firefox fork is a browser built from Mozilla’s Firefox source code. It changes the defaults, interface or bundled features, but it keeps the Gecko engine and relies on Mozilla for upstream security fixes. People choose forks for three main reasons: stricter privacy defaults, a different interface, or features that Mozilla removed or never added.

A fork’s Firefox base matters more since Mozilla’s release cadence changed. Since Firefox 155 on 1 September 2026, Mozilla has released a new version every two weeks. Firefox ESR (Extended Support Release) only gets security fixes between its major versions, and ESR 153 is the current ESR line. Forks built on ESR change slowly. Forks built on rapid releases pick up new web features as soon as Firefox does.

LibreWolf

LibreWolf is a privacy-hardened build of Firefox. It follows Firefox’s rapid releases, not the ESR branch. It removes telemetry and ships with uBlock Origin already installed.

LibreWolf also turns on Resist Fingerprinting (RFP) by default. The project’s FAQ lists the trade-offs: websites see your timezone as UTC, the theme is forced to light, and the window opens at a smaller, fixed size. LibreWolf runs on Windows, macOS and Linux. It suits Firefox users who want hardened defaults without configuring them by hand. Standard WebExtensions install as usual, so if you build your own Firefox extension, LibreWolf is a useful place to test it under strict privacy settings.

Floorp

Floorp is a Firefox fork that focuses on interface customization, with multiple sidebars and layout options that standard Firefox doesn’t have. Floorp follows Firefox’s rapid releases: version 12.21.0, released on 27 October 2026, moved to the Firefox 159 runtime, and recent releases have picked up each new Firefox version within days. Check the Floorp releases page for the latest build before you rely on any particular feature. Floorp is available for Windows, macOS and Linux. It suits users who want something close to Vivaldi but running on Gecko.

Zen Browser

Zen Browser is a Firefox fork with a minimal interface. Its split view shows several web pages side by side in one window. Zen tracks Firefox rapid releases, and the Zen release notes list version 1.24b, released on 28 October 2026, as built on Firefox 159.0. Zen runs on Windows, macOS and Linux. It suits people who keep many tabs open and want less interface clutter.

Waterfox

Waterfox is a fork based on Firefox ESR, so it changes more slowly than forks on the rapid track. Waterfox 6.7 is based on Firefox ESR 153. It adds a built-in ad blocker and tree tabs inside vertical tabs. The 6.7.0 release also turns on DNS over Oblivious HTTP (“Ultra Protection”) by default for new profiles.

Waterfox Classic is a separate, older branch that is no longer developed, so don’t use it. Waterfox runs on Windows, macOS, Linux and Android. It suits users who want a traditional Firefox experience that doesn’t change every two weeks.

Mullvad Browser

Mullvad Browser is developed by the Tor Project, which built it at Mullvad VPN’s request. It uses the same fingerprinting protection as Tor Browser, but it connects to the internet directly or through a VPN instead of the Tor network. You don’t need a Mullvad VPN subscription to use it.

Mullvad Browser 16.0 came out on 29 October 2026, the same day as Tor Browser 16.0, and is also built on Firefox ESR 153. Mullvad Browser runs on Windows 10 or later (64-bit only), macOS and Linux. It suits users who already run a VPN and want their browser to look like every other Mullvad Browser user’s.

Tor Browser

Tor Browser sends traffic through the Tor network and adds anti-fingerprinting protections. Tor Browser 16.0, released on 29 October 2026, is the first stable release built on Firefox ESR 153. The 15.0 series before it was based on ESR 140. Tor Browser is available for Windows, macOS, Linux and Android. It suits people who need anonymity, not just less tracking.

How Do Firefox Forks Affect Testing Your Site?

Hardened forks can break features on your site and change what feature detection returns. Test in standard Firefox as well as in at least one hardened fork. Forks that resist fingerprinting standardize values that pages can read, such as timezone and window size. As a result, a site that works in Firefox can behave differently in these browsers even though its code has no bug. The browser fingerprinting article explains which signals these protections target.

To compare, paste this snippet into the console in standard Firefox and then in a fork:

const ua = navigator.userAgent;
console.table({
  userAgent: ua,
  firefoxMajor: ua.match(/Firefox\/(\d+)/)?.[1] ?? 'n/a',
  timeZone: Intl.DateTimeFormat().resolvedOptions().timeZone,
  screen: `${screen.width}x${screen.height}`,
  devicePixelRatio: window.devicePixelRatio,
  hardwareConcurrency: navigator.hardwareConcurrency,
});

Gecko forks generally identify themselves as Firefox in navigator.userAgent, so analytics tools group them with Firefox. Paste the string into the OpenReplay user agent parser to see how it is classified. Keep in mind that the user agent is self-reported.

The version number also tells you little about what the browser can actually do. For example, @supports at-rule() shipped in Firefox 157, so a fork on ESR 153 doesn’t have it. Check for the capability itself instead of checking the version:

// Before: gating on a parsed version
const major = Number(navigator.userAgent.match(/Firefox\/(\d+)/)?.[1]);
if (major >= 100) enableFeature();

// After: checking the capability itself
// Returns false in browsers that don't support at-rule() or @scope
if (CSS.supports('at-rule(@scope)')) {
  enableFeature();
}

Session replay helps here too. If a replay shows a feature failing for a visitor on LibreWolf, Mullvad Browser or Tor Browser while the same flow works in standard Firefox, fingerprinting resistance is a more likely cause than a bug in your code.

Conclusion

When you compare Firefox forks, start with the Firefox base each one runs on. LibreWolf, Floorp and Zen follow rapid releases, while Waterfox, Mullvad Browser and Tor Browser are on ESR 153. Pick the fork whose defaults match how you work. For your own sites, add a hardened fork to your test matrix, run the diagnostic snippet in both browsers, and replace any version checks with feature detection.

FAQs

Can I reproduce a LibreWolf or Tor Browser bug in standard Firefox?

Partly. Set privacy.resistFingerprinting to true in about:config. This turns on the same Resist Fingerprinting code that Tor Browser enables by default, which came to Firefox through the Tor Uplift project. It can make some websites work incorrectly, so it helps you reproduce bugs that only appear in forks. It does not copy a fork's other changes, such as bundled add-ons or Tor routing.

Can I install Firefox extensions in Tor Browser?

Yes, but the Tor Project strongly advises against it. Tor Browser can install any add-on or theme that works in Firefox. However, the Tor Project only tests the add-ons that come bundled with it, and extra ones can make your browser fingerprint unique and undermine anonymity. The Tor Project offers no support for these setups, so test your extensions in standard Firefox or in a fork such as LibreWolf.

How do I test a Firefox fork without touching my main profile?

Start the fork's executable with --no-remote and --profile pointing to an empty directory. Firefox defines --profile as starting with the profile at a given path, and --no-remote implies a new instance. Do not point an ESR-based fork at a profile from current Firefox. Builds that block profile downgrades will not open profiles created by newer versions.

Do Firefox forks get security fixes as fast as Firefox?

Not always. A fork gets a security fix only after Mozilla publishes it and the fork merges it into its own build, so fork releases can come out later than Firefox releases. Rapid-release forks have to rebase onto each new Firefox version. ESR-based forks such as Waterfox and Tor Browser take their fixes from ESR point releases. To spot a gap, compare the fork's Firefox version with Mozilla's latest release.