Arize Phoenix is free, with no paid plan attached. W&B Weave 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). W&B Weave is freemium — a usable free tier with paid plans above it and is listed for agent-native tracing model with sessions, steps, tools and sub-agents as first-class concepts (not generic spans). Both sit in LLM Eval & Observability.
Arize Phoenix is the cheaper starting point: it is free, with no paid plan attached, while W&B Weave 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 W&B Weave if you need agent-native tracing model with sessions, steps, tools and sub-agents as first-class concepts (not generic spans). 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 | W&B Weave | |
|---|---|---|
| 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 | weights and biases weave, agent observability, llm tracing, evaluation framework, free tier |
| Website | phoenix.arize.com | wandb.ai |
| Full page | Arize Phoenix details → | W&B Weave details → |
| Alternatives | Arize Phoenix alternatives → | W&B Weave alternatives → |