Arize Phoenix is open source and Braintrust is not, so the question is whether you want source access and the option to fork, or would rather have a vendor accountable for it.
Eval-first platform — scorers, datasets and a playground for prompt iteration.
OpenTelemetry-native tracing and evals you can run locally.
| Braintrust | Arize Phoenix | |
|---|---|---|
| Licence | Proprietary | Open source |
| Pricing | freemium | open source |
| Self-hostable | Yes | Yes |
| Languages | Python, TypeScript | Python, TypeScript |
| Install | — | pip install arize-phoenix |
| Keys required | BRAINTRUST_API_KEY | None |
Arize Phoenix is open source and Braintrust is not, so the question is whether you want source access and the option to fork, or would rather have a vendor accountable for it. Braintrust: Eval-first platform — scorers, datasets and a playground for prompt iteration. Arize Phoenix: OpenTelemetry-native tracing and evals you can run locally.
Braintrust can run on your own infrastructure. Arize Phoenix can run on your own infrastructure.
Braintrust 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/braintrust-vs-phoenix