The Firefox browser is popular with many geeks and nerds, particularly with Linux operating systems. It is very competent and has numerous useful Add-ons and actually ranks number 4 in desktop browsers.

As with everything that is even modestly successful there are quite a number of other browsers that are based on either classic Firefox or the current version. Herein are a few of them.
Zen browser (introduced in 2025)
In early 2025, another fork of Firefox arrived called Zen browser. It has a sleeker interface and wait for it, the ability to display several web pages simultaneously. While there are add-ons to Tile windows, those simply create additional windows and let users organize them vertically / horizontally. And that is not the same as displaying tiled windows in one application window. So, I find this part the most intriguing. I was a regular user of Firefox for years and still pay bills with it. For everything else, I have been using Vivaldi since it is highly customizable AND can tile windows any way one likes. It can use Firefox add-ons and what Zen calls Mods, which are user made themes and plugins. If you like Firefox and want to try something a little different, Zen made be to your liking. Here is the link.

PaleMoon
For a fork based on classical Firefox, there is the PaleMoon browser.

Here are the main features from the website.
Main features:
- Optimized for modern processors
- Based on our own optimized layout and rendering engine, Goanna™
- Safe: forked from mature Mozilla platform code and regularly updated with the latest security patches
- Secure: Additional security features and security-aware development
- Extensible with a growing number of maintained XUL browser extensions
- Supported by our user community, and fully non-profit
- Privacy-aware: zero ads; no telemetry, spyware or data gathering
- Familiar, efficient, fully customizable interface
- Support for full themes: total freedom for any element’s design
- Smooth and speedy page drawing and script processing
- Superior gradients and fonts compared to other rendering engines
- Will continue to support NPAPI plugins like Silverlight, Adobe Flash and Java
- Extensive and growing support for existing web standards
If you liked the pre-Quantum version of Firefox, this one may interest you.
Waterfox
For a modern Firefox derivative that is more privacy and security minded, Waterfox is also worth looking into. Some of the telemetry gathered by Firefox has been removed and privacy features increased. I’m not sure if it is any faster than Firefox but just wanted to mention it for those who are regular Firefox users, so they can compare the two.

Another browser based on Firefox is LibreWolf and it compares similarly to WaterFox. Again, they are pushing for additional security and privacy.

It will take spending more time with these browsers to see if they have good enough reasons to move from Firefox.