head to head · open source
Langfuse vs Arize Phoenix
Langfuse has 34,746 GitHub stars, 3,791 forks, 926 open issues and last shipped yesterday. Arize Phoenix has 11,525 stars, 1,136 forks, 970 open issues and last shipped today. Langfuse leads on adoption by 201% (34,746 vs 11,525 stars). Langfuse is written in TypeScript under a custom or non-standard licence; Arize Phoenix is written in Python under a custom or non-standard licence. Langfuse has attracted 11% as many forks as stars, Arize Phoenix 10%. Arize Phoenix was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 3 topic tags (langchain, llm-evaluation, llmops), 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
| Langfuse | Arize Phoenix | |
|---|---|---|
| GitHub stars | ★ 35K | ★ 12K |
| License | Custom / other | Custom / other |
| Written in | TypeScript | Python |
| Last push | 2026-09-17 | 2026-09-18 |
| Forks | ⑂ 3.8K | ⑂ 1.1K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Langfuse if
- You weight community size — 35K stars and counting
- You want the Custom / other license terms
- Your stack matches TypeScript
- You value the larger contributor base for long-term maintenance
pick Arize Phoenix if
- You want the Arize Phoenix feature set and don't need the biggest community
- You prefer the Custom / other license terms
- Your stack matches Python
- You evaluated both and Arize Phoenix fits your workflow better
About Langfuse
Langfuse is an open source LLM engineering platform for building, monitoring, and improving AI powered applications. It lives in the LLMops ecosystem and provides tooling for the full development lifecycle—from prompt iteration and evaluation to observability and dataset management. Built with TypeScript and powered by ClickHouse, it enables teams to track LLM calls, user sessions, and internal logic like retrieval or agent actions in a unified interface.
read the full Langfuse overview →
About Arize Phoenix
Arize Phoenix is an open source AI observability platform for experimentation, evaluation, and troubleshooting. It lives in the machine learning infrastructure ecosystem and is written in Python. The project provides tracing, evaluation, datasets, experiments, prompt management, and a playground for LLM applications.
read the full Arize Phoenix overview →
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Frequently asked questions
Is Langfuse or Arize Phoenix more popular?
Langfuse has 34,746 GitHub stars and Arize Phoenix has 11,525. Langfuse has the larger community by that measure.
Are Langfuse and Arize Phoenix free?
Neither Langfuse nor Arize Phoenix declares a licence in this registry, so check each project's own repository before relying on either for a commercial use. Both are free to self-host.
What is the difference between Langfuse and Arize Phoenix?
Langfuse is written in TypeScript and Arize Phoenix 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, Langfuse or Arize Phoenix?
Choose Langfuse if you want the larger community (34,746 stars) or its Custom / other licence terms. Choose Arize Phoenix if its feature set, stack or Custom / other licence fits better. Both are self-hostable.