head to head · open source
ECC vs react-cosmos
ECC has 263,046 GitHub stars, 39,360 forks, 201 open issues and last shipped today. react-cosmos has 8,686 stars, 381 forks, 5 open issues and last shipped 20 days ago. ECC leads on adoption by 2,928% (263,046 vs 8,686 stars). ECC is written in JavaScript under MIT; react-cosmos is written in TypeScript under MIT. ECC has attracted 15% as many forks as stars, react-cosmos 4%. ECC was the more recently maintained of the two, and both are self-hostable with no licence fee.
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
| ECC | react-cosmos | |
|---|---|---|
| GitHub stars | ★ 263K | ★ 8.7K |
| License | MIT | MIT |
| Written in | JavaScript | TypeScript |
| Last push | 2026-09-20 | 2026-08-31 |
| Forks | ⑂ 39K | ⑂ 381 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick ECC if
- You weight community size — 263K stars and counting
- You want the MIT license terms
- Your stack matches JavaScript
- You value the larger contributor base for long-term maintenance
pick react-cosmos if
- You want the react-cosmos feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches TypeScript
- You evaluated both and react-cosmos fits your workflow better
About ECC
ECC is an MIT licensed open source agent harness performance optimization system that gives AI coding agents a coordinated engineering workflow — plan, test, implement, review, verify, remember, improve — for developers working in Claude Code, Codex, OpenCode, Cursor, and other harnesses.
About react-cosmos
React Cosmos is a sandbox for developing and testing UI components in isolation, built for React developers who want to build, render and verify individual components without launching the full application around them.
read the full react-cosmos overview →
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Frequently asked questions
Is ECC or react-cosmos more popular?
ECC has 263,046 GitHub stars and react-cosmos has 8,686. ECC has the larger community by that measure.
Are ECC and react-cosmos free?
Both are open source. ECC is licensed under MIT and react-cosmos under MIT. Neither carries a licence fee.
What is the difference between ECC and react-cosmos?
ECC is written in JavaScript and react-cosmos in TypeScript. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, ECC or react-cosmos?
Choose ECC if you want the larger community (263,046 stars) or its MIT licence terms. Choose react-cosmos if its feature set, stack or MIT licence fits better. Both are self-hostable.