head to head · open source
uBlock vs opal
uBlock has 69,033 GitHub stars, 4,427 forks, 15 open issues and last shipped yesterday. opal has 4,930 stars, 338 forks, 152 open issues and last shipped 2 months ago. uBlock leads on adoption by 1,300% (69,033 vs 4,930 stars). uBlock is written in JavaScript under GPL-3.0; opal is written in Ruby under MIT. uBlock has attracted 6% as many forks as stars, opal 7%. uBlock was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (javascript), 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 | opal | |
|---|---|---|
| GitHub stars | ★ 69K | ★ 4.9K |
| License | GPL-3.0 | MIT |
| Written in | JavaScript | Ruby |
| Last push | 2026-11-02 | 2026-09-13 |
| Forks | ⑂ 4.4K | ⑂ 338 |
| 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 opal if
- You want the opal feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches Ruby
- You evaluated both and opal 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 opal
Opal Opal is a Ruby to JavaScript source to source compiler, shipping with an implementation of the Ruby corelib and stdlib. Write Ruby, run it anywhere JavaScript runs — the browser, Node.js, Deno, Bun, QuickJS. Why Opal A real Ruby implementation. Opal ships its own corelib and stdlib and is validated against [ruby/spec][ruby spec], the same suite CRuby uses. A JavaScript host imposes limits — those are catalogued in Unsupported Features. Source to source, no runtime interpreter. Ruby compiles to plain JavaScript ahead of time, so there is no VM to download and no interpreter loop at runtime. Two way…
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Frequently asked questions
Is uBlock or opal more popular?
uBlock has 69,033 GitHub stars and opal has 4,930. uBlock has the larger community by that measure.
Are uBlock and opal free?
Both are open source. uBlock is licensed under GPL-3.0 and opal under MIT. Neither carries a licence fee.
What is the difference between uBlock and opal?
uBlock is written in JavaScript and opal in Ruby. 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 opal?
Choose uBlock if you want the larger community (69,033 stars) or its GPL-3.0 licence terms. Choose opal if its feature set, stack or MIT licence fits better. Both are self-hostable.