head to head · open source
PageIndex vs Arize Phoenix
PageIndex has 35,765 GitHub stars, 3,152 forks, 103 open issues and last shipped yesterday. Arize Phoenix has 11,544 stars, 1,140 forks, 970 open issues and last shipped yesterday. PageIndex leads on adoption by 210% (35,765 vs 11,544 stars). PageIndex is written in Python under MIT; Arize Phoenix is written in Python under a custom or non-standard licence. PageIndex has attracted 9% as many forks as stars, Arize Phoenix 10%. PageIndex was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (agents), 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
| PageIndex | Arize Phoenix | |
|---|---|---|
| GitHub stars | ★ 36K | ★ 12K |
| License | MIT | Custom / other |
| Written in | Python | Python |
| Last push | 2026-09-19 | 2026-09-19 |
| Forks | ⑂ 3.2K | ⑂ 1.1K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick PageIndex if
- You weight community size — 36K stars and counting
- You want the MIT license terms
- Your stack matches Python
- 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 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 →
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 PageIndex or Arize Phoenix more popular?
PageIndex has 35,765 GitHub stars and Arize Phoenix has 11,544. PageIndex has the larger community by that measure.
Are PageIndex and Arize Phoenix free?
Both are open source. PageIndex is licensed under MIT, and Arize Phoenix has no licence declared in this registry. Both are free to self-host.
What is the difference between PageIndex and Arize Phoenix?
PageIndex is written in Python 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, PageIndex or Arize Phoenix?
Choose PageIndex if you want the larger community (35,765 stars) or its MIT licence terms. Choose Arize Phoenix if its feature set, stack or Custom / other licence fits better. Both are self-hostable.