Weights & Biases — Observability, Prompts & Evals Platform
Observability, Prompts & EvalsLayer 4FreemiumWhat is 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.
Key Features
- ✓ML experiment tracking
- ✓Model and dataset versioning
- ✓Collaborative dashboards
- ✓Sweeps for hyperparameter tuning
- ✓Prompt monitoring and evaluation
Pros & Cons
Pros
- +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
Cons
- -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
Weights & Biases Pricing
Free trial available
- ✓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
- ✓25GB/mo Weave ingestion
- ✓Custom pricing
- ✓Advanced features
- ✓Dedicated support
- ✓SLA guarantees
Common Use Cases
ML engineers and researchers who need comprehensive experiment tracking
- •ML experiment tracking and comparison
- •Model training run management
- •Team collaboration on ML projects
- •Hyperparameter optimization
- •Model registry and versioning
Using Weights & Biases with Respan
Weights and Biases and Respan provide comprehensive ML experiment tracking and LLM observability. Track training runs with W and B while monitoring production LLM applications with Respan.
- ✓Bridge ML training insights from W and B with production LLM monitoring in Respan
- ✓Track model versioning and performance across development and deployment
- ✓Monitor prompt engineering experiments alongside traditional ML metrics
- ✓Correlate training metrics with production inference costs and performance
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Last verified: March 9, 2026