head to head · open source
Ladybird vs Mercury
Ladybird has 66,237 GitHub stars, 3,163 forks, 535 open issues and last shipped yesterday. Mercury has 1,541 stars, 42 forks, 92 open issues and last shipped 1 months ago. Ladybird leads on adoption by 4,198% (66,237 vs 1,541 stars). Ladybird is written in C++ under BSD-2-Clause; Mercury is written in JavaScript under MPL-2.0. Ladybird has attracted 5% as many forks as stars, Mercury 3%. Ladybird was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (browser), 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
| Ladybird | Mercury | |
|---|---|---|
| GitHub stars | ★ 66K | ★ 1.5K |
| License | BSD-2-Clause | MPL-2.0 |
| Written in | C++ | JavaScript |
| Last push | 2026-09-17 | 2026-08-09 |
| Forks | ⑂ 3.2K | ⑂ 42 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Ladybird if
- You weight community size — 66K stars and counting
- You want the BSD-2-Clause license terms
- Your stack matches C++
- 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 Ladybird
Ladybird is a truly independent web browser and browser engine, written from scratch in C++ rather than as a fork of any existing engine, and it is built for developers who want to work on a browser engine based on web standards while it remains in a pre alpha state.
read the full Ladybird 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 →
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Frequently asked questions
Is Ladybird or Mercury more popular?
Ladybird has 66,237 GitHub stars and Mercury has 1,541. Ladybird has the larger community by that measure.
Are Ladybird and Mercury free?
Both are open source. Ladybird is licensed under BSD-2-Clause and Mercury under MPL-2.0. Neither carries a licence fee.
What is the difference between Ladybird and Mercury?
Ladybird is written in C++ 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, Ladybird or Mercury?
Choose Ladybird if you want the larger community (66,237 stars) or its BSD-2-Clause licence terms. Choose Mercury if its feature set, stack or MPL-2.0 licence fits better. Both are self-hostable.