head to head · open source
llama_index vs Arize Phoenix
llama_index has 52,202 GitHub stars, 8,162 forks, 770 open issues and last shipped yesterday. Arize Phoenix has 11,518 stars, 1,135 forks, 970 open issues and last shipped yesterday. llama_index leads on adoption by 353% (52,202 vs 11,518 stars). llama_index is written in Python under MIT; Arize Phoenix is written in Python under a custom or non-standard licence. llama_index has attracted 16% 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 2 topic tags (agents, llamaindex), 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
| llama_index | Arize Phoenix | |
|---|---|---|
| GitHub stars | ★ 52K | ★ 12K |
| License | MIT | Custom / other |
| Written in | Python | Python |
| Last push | 2026-09-17 | 2026-09-17 |
| Forks | ⑂ 8.2K | ⑂ 1.1K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick llama_index if
- You weight community size — 52K 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 llama_index
LlamaIndex is an MIT licensed, open source Python framework for building agentic applications — retrieval augmented generation systems, agents and multi agent workflows — on top of private documents and data, and it is aimed at AI engineers and teams who need to connect large language models to their own sources of context.
read the full llama_index 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 llama_index or Arize Phoenix more popular?
llama_index has 52,202 GitHub stars and Arize Phoenix has 11,518. llama_index has the larger community by that measure.
Are llama_index and Arize Phoenix free?
Both are open source. llama_index 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 llama_index and Arize Phoenix?
llama_index 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, llama_index or Arize Phoenix?
Choose llama_index if you want the larger community (52,202 stars) or its MIT licence terms. Choose Arize Phoenix if its feature set, stack or Custom / other licence fits better. Both are self-hostable.