Weights & Biases

Weights & Biases is the developer platform for machine-learning and AI teams, used to track experiments, version datasets and models, evaluate results and manage the path from research to production. Founded in 2017 by Lukas Biewald and Chris Van Pelt (previously co-founders of CrowdFlower/Figure Eight) and headquartered in San Francisco, W&B became a de facto standard for ML experiment tracking, adopted across research labs and enterprise ML organisations and integrated with the major training frameworks. Its product line spans Models (experiment tracking, sweeps, model registry) and Weave (LLM application evaluation and tracing). The company raised roughly $395M across five rounds, reaching a $1.25B valuation in 2023. In March 2025 CoreWeave agreed to acquire Weights & Biases — reported at about $1.7B — and completed the acquisition on 5 May 2025; the platform continues to operate as part of CoreWeave's AI cloud.