Weights & Biases

Weights & Biases (often written W&B) is the most widely used platform for tracking machine-learning experiments. As teams train and tune models, W&B logs every run — hyperparameters, metrics, datasets, and results — so the work is reproducible and comparable rather than scattered across notebooks. Its newer Weave product extends the same idea to large-language-model applications, adding tracing and evaluation for AI features in production. W&B was acquired by the AI cloud provider CoreWeave in 2025 but continues as a distinct product used across the AI industry.