Arize Phoenix vs W&B Weave
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
AI tool · Open source
An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry.
AI tool · Freemium
Weights & Biases' toolkit for tracing, evaluating and comparing LLM application versions.
The short answer
Choose Arize Phoenix if you need…
- Local debugging of LLM traces
- OpenTelemetry-based stacks
Choose W&B Weave if you need…
- Teams already on Weights & Biases
- Evaluation leaderboards across versions
Side-by-side
| Arize Phoenix | W&B Weave | |
|---|---|---|
| Type | Prompting · Evaluation & observability | Prompting · Evaluation & observability |
| Price | Open source | Freemium |
| Platforms | Self-hosted, Web, API | Web, API |
| Works with | LangChain, LlamaIndex, OpenAI | OpenAI, Anthropic |
| Hands-on tested by us | Not yet | Not yet |
| Last checked | 2026-10-29 | 2026-10-29 |
What each one is
Arize Phoenix
An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry. Standards-based and free to run locally. Enterprise features live in Arize's paid platform.
W&B Weave
Weights & Biases' toolkit for tracing, evaluating and comparing LLM application versions. Natural fit for ML teams using W&B. Feels heavier than lighter-weight tools for small projects.
Best for
Arize Phoenix
- Local debugging of LLM traces
- OpenTelemetry-based stacks
W&B Weave
- Teams already on Weights & Biases
- Evaluation leaderboards across versions
Strengths
Arize Phoenix
- OpenTelemetry tracing
- LLM-as-judge evals
- Prompt playground
- Datasets and experiments
W&B Weave
- Automatic call tracing
- Evaluation framework
- Version comparison
- Scorers and guardrails
Frequently asked questions
What is the difference between Arize Phoenix and W&B Weave?
Arize Phoenix: An open-source tool for tracing, evaluating and experimenting with LLM and agent applications, built on OpenTelemetry. W&B Weave: Weights & Biases' toolkit for tracing, evaluating and comparing LLM application versions. Arize Phoenix suits local debugging of llm traces, while W&B Weave suits teams already on weights & biases.
Are Arize Phoenix and W&B Weave free?
Arize Phoenix: Open source. W&B Weave: Freemium.
What are other alternatives to Arize Phoenix and W&B Weave?
Other options people compare them with include Langfuse, Confident AI (DeepEval), LangSmith, Opik, promptfoo.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.