head to head · open source
faiss vs Langfuse
faiss has 40,929 GitHub stars, 4,526 forks, 327 open issues and last shipped yesterday. Langfuse has 34,746 stars, 3,791 forks, 926 open issues and last shipped 2 days ago. faiss leads on adoption by 18% (40,929 vs 34,746 stars). faiss is written in C++ under MIT; Langfuse is written in TypeScript under a custom or non-standard licence. faiss has attracted 11% as many forks as stars, Langfuse 11%. faiss 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
| faiss | Langfuse | |
|---|---|---|
| GitHub stars | ★ 41K | ★ 35K |
| License | MIT | Custom / other |
| Written in | C++ | TypeScript |
| Last push | 2026-09-18 | 2026-09-17 |
| Forks | ⑂ 4.5K | ⑂ 3.8K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick faiss if
- You weight community size — 41K stars and counting
- You want the MIT license terms
- Your stack matches C++
- You value the larger contributor base for long-term maintenance
pick Langfuse if
- You want the Langfuse feature set and don't need the biggest community
- You prefer the Custom / other license terms
- Your stack matches TypeScript
- You evaluated both and Langfuse fits your workflow better
About faiss
Faiss is an MIT licensed C++ library for efficient similarity search and clustering of dense vectors, with complete Python and NumPy wrappers, developed primarily at Meta's Fundamental AI Research group, and it is intended for engineers and researchers who need nearest neighbour search over vector sets that range from small collections to sets that possibly do not fit in RAM.
read the full faiss overview →
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 →
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Frequently asked questions
Is faiss or Langfuse more popular?
faiss has 40,929 GitHub stars and Langfuse has 34,746. faiss has the larger community by that measure.
Are faiss and Langfuse free?
Both are open source. faiss is licensed under MIT, and Langfuse has no licence declared in this registry. Both are free to self-host.
What is the difference between faiss and Langfuse?
faiss is written in C++ and Langfuse 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, faiss or Langfuse?
Choose faiss if you want the larger community (40,929 stars) or its MIT licence terms. Choose Langfuse if its feature set, stack or Custom / other licence fits better. Both are self-hostable.