Weights & Biases (W&B) is the AI developer platform that the world's leading machine learning teams use to build, train, and deploy better models faster. Founded in 2017 in San Francisco, W&B provides experiment tracking, model management, and LLMOps tooling used by over 1 million developers - from OpenAI and Meta to Toyota and AstraZeneca. Acquired by CoreWeave in May 2025 for $1.7 billion, W&B is now the software backbone of one of the most important AI infrastructure companies in the world.
Humanloop was an enterprise LLM development platform founded in 2020 as a UCL spinout, offering prompt management, evaluations, and observability tools for teams building AI applications. With customers like Duolingo and Gusto, it raised ~$8M and reached ~$3.8M ARR before being acqui-hired by Anthropic in August 2025, after which the platform was sunsetted on September 8, 2025. Its technology and team live on inside Anthropic's enterprise console.