Langfuse 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 LLM engineering platform for tracing, prompt management, evaluations and cost tracking.
AI tool · Freemium
Weights & Biases' toolkit for tracing, evaluating and comparing LLM application versions.
The short answer
Choose Langfuse if you need…
- Tracing LLM apps in production
- Self-hosted prompt management
Choose W&B Weave if you need…
- Teams already on Weights & Biases
- Evaluation leaderboards across versions
Side-by-side
| Langfuse | W&B Weave | |
|---|---|---|
| Type | Prompting · Evaluation & observability | Prompting · Evaluation & observability |
| Price | Open source | Freemium |
| Platforms | Web, Self-hosted, API | Web, API |
| Works with | LangChain, OpenAI, LlamaIndex | OpenAI, Anthropic |
| Hands-on tested by us | Not yet | Not yet |
| Last checked | 2026-10-29 | 2026-10-29 |
What each one is
Langfuse
An open-source LLM engineering platform for tracing, prompt management, evaluations and cost tracking. A popular, well-documented default for observability. Self-hosting at scale needs some operational effort.
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
Langfuse
- Tracing LLM apps in production
- Self-hosted prompt management
W&B Weave
- Teams already on Weights & Biases
- Evaluation leaderboards across versions
Strengths
Langfuse
- Traces and spans for LLM calls
- Prompt management with versions
- Evals and datasets
- Cost and latency dashboards
W&B Weave
- Automatic call tracing
- Evaluation framework
- Version comparison
- Scorers and guardrails
Frequently asked questions
What is the difference between Langfuse and W&B Weave?
Langfuse: An open-source LLM engineering platform for tracing, prompt management, evaluations and cost tracking. W&B Weave: Weights & Biases' toolkit for tracing, evaluating and comparing LLM application versions. Langfuse suits tracing llm apps in production, while W&B Weave suits teams already on weights & biases.
Are Langfuse and W&B Weave free?
Langfuse: Open source. W&B Weave: Freemium.
What are other alternatives to Langfuse and W&B Weave?
Other options people compare them with include Arize Phoenix, 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.