head to head · open source
ponytail vs opik
ponytail has 141,230 GitHub stars, 7,572 forks, 270 open issues and last shipped 4 days ago. opik has 22,098 stars, 1,801 forks, 258 open issues and last shipped yesterday. ponytail leads on adoption by 539% (141,230 vs 22,098 stars). ponytail is written in JavaScript under MIT; opik is written in Python under Apache-2.0. ponytail has attracted 5% as many forks as stars, opik 8%. opik was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (llm), 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
| ponytail | opik | |
|---|---|---|
| GitHub stars | ★ 141K | ★ 22K |
| License | MIT | Apache-2.0 |
| Written in | JavaScript | Python |
| Last push | 2026-09-14 | 2026-09-17 |
| Forks | ⑂ 7.6K | ⑂ 1.8K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick ponytail if
- You weight community size — 141K stars and counting
- You want the MIT license terms
- Your stack matches JavaScript
- You value the larger contributor base for long-term maintenance
pick opik if
- You want the opik feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Python
- You evaluated both and opik fits your workflow better
About ponytail
Ponytail is an open source agent skill for JavaScript and LLM based coding tools that makes an AI agent write the minimum working code for a task, and it is built for developers and teams running agents such as Claude Code, Codex, or Cursor against real repositories.
read the full ponytail overview →
About opik
Opik is open source LLM observability, evaluation, and AI agent tracing platform for teams building LLM apps, RAG systems, and agentic workflows, built by Comet, Apache 2.0 licensed, free to self host full platform.
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Frequently asked questions
Is ponytail or opik more popular?
ponytail has 141,230 GitHub stars and opik has 22,098. ponytail has the larger community by that measure.
Are ponytail and opik free?
Both are open source. ponytail is licensed under MIT and opik under Apache-2.0. Neither carries a licence fee.
What is the difference between ponytail and opik?
ponytail is written in JavaScript and opik in Python. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, ponytail or opik?
Choose ponytail if you want the larger community (141,230 stars) or its MIT licence terms. Choose opik if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.