The deciding difference is operational: Arize Phoenix can run on infrastructure you control, LangSmith cannot. If that constraint is real for you, it settles the choice before anything else is considered.
Tracing, datasets and evals from the LangChain team.
OpenTelemetry-native tracing and evals you can run locally.
| LangSmith | Arize Phoenix | |
|---|---|---|
| Licence | Proprietary | Open source |
| Pricing | freemium | open source |
| Self-hostable | No | Yes |
| Languages | Python, TypeScript | Python, TypeScript |
| Install | — | pip install arize-phoenix |
| Keys required | LANGSMITH_API_KEY | None |
The deciding difference is operational: Arize Phoenix can run on infrastructure you control, LangSmith cannot. If that constraint is real for you, it settles the choice before anything else is considered. LangSmith: Tracing, datasets and evals from the LangChain team. Arize Phoenix: OpenTelemetry-native tracing and evals you can run locally.
LangSmith is a hosted service only. Arize Phoenix can run on your own infrastructure.
LangSmith is proprietary (freemium). Arize Phoenix is open source (open source).
Every page here answers to Accept: text/markdown and returns the same content at roughly a tenth the tokens. No separate site, no toggle — same URL.
curl -s -H "Accept: text/markdown" https://newagent.build/compare/langsmith-vs-phoenix