head to head · open source
faiss vs xerj
faiss has 41,251 GitHub stars, 4,584 forks, 327 open issues and last shipped 2 days ago. xerj has 18,817 stars, 1,435 forks, 16 open issues and last shipped yesterday. faiss leads on adoption by 119% (41,251 vs 18,817 stars). faiss is written in C++ under MIT; xerj is written in Rust under Apache-2.0. faiss has attracted 11% as many forks as stars, xerj 8%. xerj 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 | xerj | |
|---|---|---|
| GitHub stars | ★ 41K | ★ 19K |
| License | MIT | Apache-2.0 |
| Written in | C++ | Rust |
| Last push | 2026-11-01 | 2026-11-02 |
| Forks | ⑂ 4.6K | ⑂ 1.4K |
| 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 xerj if
- You want the xerj feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Rust
- You evaluated both and xerj fits your workflow better
About faiss
Faiss Faiss is a library for efficient similarity search and clustering of dense vectors. It contains algorithms that search in sets of vectors of any size, up to ones that possibly do not fit in RAM. It also contains supporting code for evaluation and parameter tuning. Faiss is written in C++ with complete wrappers for Python/numpy. Some of the most useful algorithms are implemented on the GPU. It is developed primarily at Meta's Fundamental AI Research group. News See CHANGELOG.md for detailed information about latest features. Introduction Faiss contains several methods for similarity search. It assumes that…
read the full faiss overview →
About xerj
XERJ XERJ is a community trusted local AI search that indexes any folder automatically, so your coding agent stops burning tokens reading files one by one and pulls the exact code it needs instead. Reference coding is its main use case and the clearest win: point an agent at a task and it downloads the open source repos closest to it, indexes them, and reuses how they solved the problem before writing its own code. In a controlled study that cut a coding agent's output tokens by 2.7x at the same 16/16 solve rate (case study), and people report roughly 5x in everyday work (field reports). It is enough for a…
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Frequently asked questions
Is faiss or xerj more popular?
faiss has 41,251 GitHub stars and xerj has 18,817. faiss has the larger community by that measure.
Are faiss and xerj free?
Both are open source. faiss is licensed under MIT and xerj under Apache-2.0. Neither carries a licence fee.
What is the difference between faiss and xerj?
faiss is written in C++ and xerj in Rust. 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 xerj?
Choose faiss if you want the larger community (41,251 stars) or its MIT licence terms. Choose xerj if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.