head to head · open source
vllm vs Arize Phoenix
vllm has 96,158 GitHub stars, 24,317 forks, 7,953 open issues and last shipped yesterday. Arize Phoenix has 12,106 stars, 1,258 forks, 970 open issues and last shipped yesterday. vllm leads on adoption by 694% (96,158 vs 12,106 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 25% 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 | ★ 96K | ★ 12K |
| License | Apache-2.0 | Custom / other |
| Written in | Python | Python |
| Last push | 2026-11-02 | 2026-11-02 |
| Forks | ⑂ 24K | ⑂ 1.3K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick vllm if
- You weight community size — 96K 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
Easy, fast, and cheap LLM serving for everyone 🔥 We have built a vLLM website to help you get started with vLLM. Please visit vllm.ai to learn more. For events, please visit vllm.ai/events to join us. About vLLM is a fast and easy to use library for LLM inference and serving. Originally developed in the Sky Computing Lab at UC Berkeley, vLLM has grown into one of the most active open source AI projects built and maintained by a diverse community of many dozens of academic institutions and companies from over 2000 contributors. vLLM is fast with: State of the art serving throughput Efficient management of…
About Arize Phoenix
English · 简体中文 Arize Phoenix is Arize's open source AI observability platform designed for experimentation, evaluation, and troubleshooting. For managed production workflows, Arize also offers Arize AX. Phoenix provides: Tracing Trace your LLM application's runtime using OpenTelemetry based instrumentation. Evaluation Leverage LLMs to benchmark your application's performance using response and retrieval evals. Datasets Create versioned datasets of examples for experimentation, evaluation, and fine tuning. Experiments Track and evaluate changes to prompts, LLMs, and retrieval. Playground Optimize prompts, compare…
read the full Arize Phoenix overview →
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Frequently asked questions
Is vllm or Arize Phoenix more popular?
vllm has 96,158 GitHub stars and Arize Phoenix has 12,106. 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 (96,158 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.