Arize Phoenix is free, with no paid plan attached. Braintrust is freemium — a usable free tier with paid plans above it. Both are listed under LLM Eval & Observability, so this is a like-for-like comparison. Neither is ranked above the other — Flocci carries no sponsored placement.
Arize Phoenix is free, with no paid plan attached and is listed for fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported). Braintrust is freemium — a usable free tier with paid plans above it and is listed for free Starter plan ships model credits and scored evals with no card required. Both sit in LLM Eval & Observability.
Arize Phoenix is the cheaper starting point: it is free, with no paid plan attached, while Braintrust is freemium — a usable free tier with paid plans above it. Pricing tiers here come from the catalog, not from a promotional page.
Choose Arize Phoenix if you need fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported); choose Braintrust if you need free Starter plan ships model credits and scored evals with no card required. Flocci AI Tools does not rank one above the other — it shows both feature sets side by side and lets the requirement decide.
| Arize Phoenix | Braintrust | |
|---|---|---|
| Pricing tier | Free | Free tier + paid plans |
| Free to start | Yes | Yes |
| Category | AI Models & Local Execution | AI Models & Local Execution |
| Type | LLM Eval & Observability | LLM Eval & Observability |
| Listed capabilities |
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| Tags | arize phoenix, llm observability open source, tracing, evaluation, rag debugging, free | braintrust, llm eval platform, prompt playground, ai evaluation, free tier, scoring |
| Website | phoenix.arize.com | braintrust.dev |
| Full page | Arize Phoenix details → | Braintrust details → |
| Alternatives | Arize Phoenix alternatives → | Braintrust alternatives → |