LibreWolf is a privacy-focused, community-maintained desktop browser forked from Firefox, independent of Mozilla. Cookies and history are deleted automatically when the browser is closed and Firefox Sync is disabled by default. Another strong point is that it doesn't include telemetry and automatic updates. A standalone launcher to check and install updates is available.

Floorp is a Firefox-based browser focused on privacy & customization. It's open source, developed by the Japanese community Ablaze, available for Windows, Mac and Linux. The current version 11 is based on Firefox 128 Extended Support Release (ESR), but v12, as announced in February 2025, will adopt Rapid Release Firefox. The software offers extensions support, vertical tabs and many custom features similar to Vivaldi.

Zen Browser is a different kind of browser that lets you focus on the web without distraction. It's built on latest Firefox version with many customizations and security features, such as vertical tabs, Split View, workspaces, compact mode which hides the tab bar to focus on the webpage and Glance, a quick preview of a website without leaving your current page.

IronFox is a fork of Mull , the Firefox-based mobile browser that was developed by DivestOS before its closure. It offers the same familiar interface of Firefox Mobile providing a free and open source, privacy and security-oriented Android browser for daily use. A new version of IronFox is released closely after every Firefox update.

Iceraven is an open source mobile browser for Android, based on Mozilla's Fenix version of Firefox. It's similar to Ironfox and has several custom features such as about:config support, tab suspension option and Homepage customization. Its updates aren't as quick as Ironfox ones, however the developer is progressingly increasing its release speed.

Betterbird is a soft fork of Mozilla Thunderbird, which means that it stays in sync with Thunderbird’s updates and security improvements. Also it contains new features and provides exclusive bug fixes before the original program. The program is open source and maintained by Jörg Knobloch, Thunderbird’s first employee, who was ousted and banned from the for-profit MZLA Technologies Corporation after his concerns with some of the new policies.

FairEmail is an opensource, privacy-friendly email client that is a good alternative to both Thunderbird and Gmail app on Android. It supports OpenPGP and S/MIME encryption, unlimited accounts, swipe gestures and email scheduling. It also offers security measures like Biometric authentication, Safe message view and reformatting emails to avoid phishing.