head to head · open source
uBlock vs Mercury
uBlock has 69,033 GitHub stars, 4,427 forks, 15 open issues and last shipped yesterday. Mercury has 1,542 stars, 43 forks, 92 open issues and last shipped 3 months ago. uBlock leads on adoption by 4,377% (69,033 vs 1,542 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.
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Side by side
| uBlock | Mercury | |
|---|---|---|
| GitHub stars | ★ 69K | ★ 1.5K |
| License | GPL-3.0 | MPL-2.0 |
| Written in | JavaScript | JavaScript |
| Last push | 2026-11-02 | 2026-08-09 |
| Forks | ⑂ 4.4K | ⑂ 43 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick uBlock if
- You weight community size — 69K 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
[![Badge Commits]][Commit Rate] [![Badge Issues]][Issues] [![Badge Localization]][Crowdin] [![Badge License]][License] [![Badge NPM]][NPM] [![Badge Mozilla]][Mozilla] ![Badge Chrome] [![Badge Edge]][Edge] uBlock Origin (uBO) GitHub Releases Stable and development versions on Firefox, Chromium MV2, and Thunderbird. Must be placed manually into web browsers; the Chromium and Thunderbird versions usually won't auto update. Related: uBlock Origin Lite uBlock Origin (uBO) is a CPU and memory efficient [wide spectrum content blocker][Blocking] for Chromium and Firefox. It blocks ads, trackers, coin miners, popups…
read the full uBlock overview →
About Mercury
Mercury Browser Firefox fork with compiler optimizations and patches from Librewolf, Waterfox, Ghostery, and BetterFox. It aims to be the Firefox equivalent of my main project: Thorium (a Chromium fork). Patches See PATCHES.md Bugs See BUGS.md Building See BUILDING.md and DEBUGGING.md.
read the full Mercury overview →
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Frequently asked questions
Is uBlock or Mercury more popular?
uBlock has 69,033 GitHub stars and Mercury has 1,542. 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 (69,033 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.