Arize Phoenix is free, with no paid plan attached. Promptfoo 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). Promptfoo is freemium — a usable free tier with paid plans above it and is listed for open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI. Both sit in LLM Eval & Observability.
Arize Phoenix is the cheaper starting point: it is free, with no paid plan attached, while Promptfoo 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 Promptfoo if you need open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI. 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 | Promptfoo | |
|---|---|---|
| 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 |
|
|
| Tags | arize phoenix, llm observability open source, tracing, evaluation, rag debugging, free | promptfoo, prompt testing, llm red teaming, eval framework, open source, free, ci for prompts |
| Website | phoenix.arize.com | promptfoo.dev |
| Full page | Arize Phoenix details → | Promptfoo details → |
| Alternatives | Arize Phoenix alternatives → | Promptfoo alternatives → |