Langfuse vs Weights & Biases: Observability, Prompts & Evals Comparison
Compare Langfuse and Weights & Biases side by side. Both are tools in the Observability, Prompts & Evals category.
Updated March 9, 2026
The short answer
Choose Langfuse if fully open-source with MIT license and free for commercial use with no usage limits.
Choose Weights & Biases if free tier for personal projects and academic research provides excellent value.
Want to compare Langfuse and Weights & Biases on your own traffic?
Respan lets you trace LLM and agent calls across any model or framework, A/B test prompts on production traffic, and route requests across 250+ models through one gateway. Free tier covers 10K traces per month. Setup in 5 minutes, no credit card.
Quick Comparison
| Category | Observability, Prompts & Evals | Observability, Prompts & Evals |
| Pricing | Open Source | Freemium |
| Best For | Teams who want open-source LLM observability they can self-host and customize | ML engineers and researchers who need comprehensive experiment tracking |
| Website | langfuse.com | wandb.ai |
| Key Features |
|
|
| Use Cases |
|
|
Pros & Cons: Langfuse vs Weights & Biases
- +Fully open-source with MIT license and free for commercial use with no usage limits
- +Acquired by ClickHouse in January 2026, providing strong backing and future investment
- +Active development with strong community support and comprehensive documentation
- +Transparent pricing model based on units rather than complex metric calculations
- +Deep integrations with major frameworks like LangChain, OpenAI, and LlamaIndex
- −Recent acquisition by ClickHouse may lead to platform changes and strategic shifts
- −Smaller team of 7 employees may impact support capacity
- −Enterprise pricing at $3,450-$5,700/month can be expensive for mid-sized teams
- +Free tier for personal projects and academic research provides excellent value
- +Comprehensive experiment tracking and model versioning capabilities
- +Strong visualization tools help teams understand model performance
- +Acquisition by CoreWeave provides infrastructure synergies and stability
- −Pricing can become expensive for large teams and enterprises
- −Additional storage costs can add up quickly for data-intensive workflows
- −Learning curve for advanced features may slow initial adoption
- −Platform complexity may be overkill for simple ML projects
Pricing: Langfuse vs Weights & Biases
- · Personal projects
- · Limited storage
- · Community support
- · Core features
- · Full product features
- · Enhanced storage
- · Email support
- · Team collaboration
- · For academic research
- · Unlimited tracked hours
- · 200GB cloud storage
- · Up to 100 seats
- · Custom pricing
- · Advanced features
- · Dedicated support
- · SLA guarantees
When to Choose Langfuse vs Weights & Biases
- Self-hosted LLM monitoring
- Open-source tracing for AI applications
- Prompt versioning and management
- ML experiment tracking and comparison
- Model training run management
- Team collaboration on ML projects
About Langfuse
Langfuse is an open-source LLM engineering platform that provides comprehensive tools for traces, evaluations, prompt management, and metrics to debug and improve LLM applications. Founded in Berlin, Germany in 2022, Langfuse quickly became a leading platform in the LLM observability space. The platform features MIT-licensed open-source core with no usage limits for commercial use, making it highly accessible to teams of all sizes. Langfuse offers deep integration with popular frameworks including LangChain, OpenAI, LlamaIndex, and LiteLLM. The platform provides detailed tracing capabilities, evaluation tools, comprehensive prompt management, and rich metrics tracking. In January 2026, Langfuse was acquired by ClickHouse, Inc., marking a significant transatlantic venture exit and validating the platform's technology and market position. The acquisition demonstrates the value of Langfuse's approach to LLM observability, evaluations, and prompt management.
About Weights & Biases
Weights and Biases (W and B) is a machine learning operations platform founded in 2017 by Chris Van Pelt, Lukas Biewald, and Shawn Lewis in San Francisco, California. The platform offers performance visualization tools for machine learning, helping companies track models, visualize performance, and automate training and model improvement workflows. W and B provides comprehensive experiment tracking, model versioning, and collaborative tools for ML teams. In March 2025, Weights and Biases was acquired by CoreWeave, strengthening its position in the AI infrastructure ecosystem. The company raised a total of USD 250M from investors including CoreWeave, Coatue, Bloomberg Beta, and Insight Partners. W and B offers a free tier for personal projects and provides academic institutions with free Pro licenses for non-profit research, including unlimited tracked hours, 200GB cloud storage, up to 25GB/month of Weave data ingestion, and up to 100 seats. Paid plans start at USD 60/month with additional cloud storage available at USD 0.03 per GB.
What is Observability, Prompts & Evals?
Tools for monitoring LLM applications in production, managing and versioning prompts, and evaluating model outputs. Includes tracing, logging, cost tracking, prompt engineering platforms, automated evaluation frameworks, and human annotation workflows.
Browse all Observability, Prompts & Evalstools →Other Observability, Prompts & Evals Tools
More Observability, Prompts & Evals Comparisons
Run Observability, Prompts & Evals in production with Respan
One platform for routing, observability, tracing, and evals across every LLM provider.