head to head · open source
faiss vs PageIndex
faiss has 40,929 GitHub stars, 4,526 forks, 327 open issues and last shipped yesterday. PageIndex has 35,696 stars, 3,147 forks, 103 open issues and last shipped 2 days ago. faiss leads on adoption by 15% (40,929 vs 35,696 stars). faiss is written in C++ under MIT; PageIndex is written in Python under MIT. faiss has attracted 11% as many forks as stars, PageIndex 9%. 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 | PageIndex | |
|---|---|---|
| GitHub stars | ★ 41K | ★ 36K |
| License | MIT | MIT |
| Written in | C++ | Python |
| Last push | 2026-09-18 | 2026-09-17 |
| Forks | ⑂ 4.5K | ⑂ 3.1K |
| 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 PageIndex if
- You want the PageIndex feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches Python
- You evaluated both and PageIndex 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 PageIndex
PageIndex is a vectorless, reasoning based retrieval augmented generation engine written in Python and released under the MIT license. It lives in the AI and machine learning infrastructure ecosystem, with topics spanning RAG, information retrieval, LLM reasoning, context engineering, and agentic AI. Instead of building a vector index, PageIndex generates a hierarchical tree index for each document and then lets a large language model reason its way through that tree, in the same way a human expert turns to the right section of a long report. The project ships as a Python SDK, a hosted cloud service, and a docume…
read the full PageIndex overview →
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Frequently asked questions
Is faiss or PageIndex more popular?
faiss has 40,929 GitHub stars and PageIndex has 35,696. faiss has the larger community by that measure.
Are faiss and PageIndex free?
Both are open source. faiss is licensed under MIT and PageIndex under MIT. Neither carries a licence fee.
What is the difference between faiss and PageIndex?
faiss is written in C++ and PageIndex 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, faiss or PageIndex?
Choose faiss if you want the larger community (40,929 stars) or its MIT licence terms. Choose PageIndex if its feature set, stack or MIT licence fits better. Both are self-hostable.