head to head · open source
uBlock vs Mercury
uBlock has 67,923 GitHub stars, 4,353 forks, 15 open issues and last shipped yesterday. Mercury has 1,541 stars, 42 forks, 92 open issues and last shipped 1 months ago. uBlock leads on adoption by 4,308% (67,923 vs 1,541 stars). uBlock is written in JavaScript under GPL-3.0; Mercury is written in JavaScript under MPL-2.0. uBlock has attracted 6% as many forks as stars, Mercury 3%. uBlock was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (firefox), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
← all 8884 open source comparisons
Side by side
| uBlock | Mercury | |
|---|---|---|
| GitHub stars | ★ 68K | ★ 1.5K |
| License | GPL-3.0 | MPL-2.0 |
| Written in | JavaScript | JavaScript |
| Last push | 2026-09-17 | 2026-08-09 |
| Forks | ⑂ 4.4K | ⑂ 42 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick uBlock if
- You weight community size — 68K stars and counting
- You want the GPL-3.0 license terms
- Your stack matches JavaScript
- You value the larger contributor base for long-term maintenance
pick Mercury if
- You want the Mercury feature set and don't need the biggest community
- You prefer the MPL-2.0 license terms
- Your stack matches JavaScript
- You evaluated both and Mercury fits your workflow better
About uBlock
uBlock Origin is a CPU and memory efficient, wide spectrum content blocker for Chromium and Firefox, aimed at anyone who wants ads, trackers, coin miners, popups, anti blockers and malware sites neutralised by default without hand tuning anything.
read the full uBlock overview →
About Mercury
Mercury is a web browser project in the Firefox ecosystem. It is a fork of Firefox that combines compiler optimizations with patches from Librewolf, Waterfox, Ghostery, and BetterFox. The project describes itself as the Firefox equivalent of Thorium, which is a Chromium fork. Mercury is licensed under MPL 2.0, and its repository topics include browser, privacy, optimization, and Firefox fork.
read the full Mercury overview →
More in Productivity & Utilities
Related comparisons
More Browsers & Extensions projects
Compare either of these against the rest of the Browsers & Extensions field.
Frequently asked questions
Is uBlock or Mercury more popular?
uBlock has 67,923 GitHub stars and Mercury has 1,541. uBlock has the larger community by that measure.
Are uBlock and Mercury free?
Both are open source. uBlock is licensed under GPL-3.0 and Mercury under MPL-2.0. Neither carries a licence fee.
What is the difference between uBlock and Mercury?
uBlock is written in JavaScript and Mercury in JavaScript. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, uBlock or Mercury?
Choose uBlock if you want the larger community (67,923 stars) or its GPL-3.0 licence terms. Choose Mercury if its feature set, stack or MPL-2.0 licence fits better. Both are self-hostable.