head to head · open source
vllm vs Arize Phoenix
vllm has 92,028 GitHub stars, 22,335 forks, 7,953 open issues and last shipped yesterday. Arize Phoenix has 11,518 stars, 1,135 forks, 970 open issues and last shipped yesterday. vllm leads on adoption by 699% (92,028 vs 11,518 stars). vllm is written in Python under Apache-2.0; Arize Phoenix is written in Python under a custom or non-standard licence. vllm has attracted 24% 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.
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
| vllm | Arize Phoenix | |
|---|---|---|
| GitHub stars | ★ 92K | ★ 12K |
| License | Apache-2.0 | Custom / other |
| Written in | Python | Python |
| Last push | 2026-09-17 | 2026-09-17 |
| Forks | ⑂ 22K | ⑂ 1.1K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick vllm if
- You weight community size — 92K stars and counting
- You want the Apache-2.0 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 vllm
vLLM is a high throughput, memory efficient Python library for LLM inference and serving, built for ML engineers and platform teams who need to run open weight models on their own hardware at production scale.
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 vllm or Arize Phoenix more popular?
vllm has 92,028 GitHub stars and Arize Phoenix has 11,518. vllm has the larger community by that measure.
Are vllm and Arize Phoenix free?
Both are open source. vllm is licensed under Apache-2.0, and Arize Phoenix has no licence declared in this registry. Both are free to self-host.
What is the difference between vllm and Arize Phoenix?
vllm 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, vllm or Arize Phoenix?
Choose vllm if you want the larger community (92,028 stars) or its Apache-2.0 licence terms. Choose Arize Phoenix if its feature set, stack or Custom / other licence fits better. Both are self-hostable.