# Weights & Biases

> Weights & Biases (W&B) is the leading AI developer platform for machine learning and generative AI, offering tools for experiment tracking, hyperparameter optimization, model registry, and LLM application development. Founded in 2017 by Lukas Biewald, Chris Van Pelt, and Shawn Lewis in San Francisco, W&B powers over 1 million developers and 1,400+ organizations — including OpenAI, Meta, and NVIDIA — by making it easier to build, train, evaluate, and deploy AI models. Acquired by CoreWeave for ~$1.7B in May 2025, W&B continues expanding its platform with Weave for LLM/agent observability, cementing its position as the de facto infrastructure for modern AI development.

- **Founded:** 2017
- **Headquarters:** San Francisco, California, USA
- **Founders:** Lukas Biewald (CEO & Co-founder), Chris Van Pelt (Co-founder), Shawn Lewis (Co-founder & CTO)
- **Team size:** 201–500 employees (LinkedIn range; ~250–302 per headcount estimates)
- **Products:** W&B Models, W&B Weave, W&B Inference, Mission Control, W&B Registry
- **Notable:** Reached unicorn ($1B+) valuation in August 2023 with Series C funding, Acquired by CoreWeave for ~$1.7B in May 2025 — one of the largest AI developer tooling acquisitions, Used by OpenAI during GPT-4 training, managing 2,000+ projects and millions of experiments

## Products & services

- **W&B Models** — Flagship MLOps product covering the full model lifecycle — experiment tracking (Runs), automated hyperparameter optimization (Sweeps), dataset and model versioning (Artifacts), centralized model registry, collaborative dashboards (Reports), and ML job execution (Launch).
- **W&B Weave** — LLM and GenAI application toolkit for building and iterating on AI agents and pipelines — includes tracing, rigorous evaluations, online monitoring, prompt playground, and guardrails. GA for enterprises as of December 2024. Open source on GitHub.
- **W&B Inference** — Inference serving product announced in preview at Fully Connected 2025, integrated with CoreWeave's infrastructure.
- **Mission Control** — Infrastructure observability integration announced in preview at Fully Connected 2025, unifying CoreWeave compute monitoring with W&B model training visibility.
- **W&B Registry** — Curated central repository for models and datasets with versioning, aliases, lineage tracking, and governance controls — serves as the single source of truth for production AI assets.

## Achievements

- Reached unicorn ($1B+) valuation in August 2023 with Series C funding
- Acquired by CoreWeave for ~$1.7B in May 2025 — one of the largest AI developer tooling acquisitions
- Used by OpenAI during GPT-4 training, managing 2,000+ projects and millions of experiments
- Integrated into 20,000+ open-source repositories including LangChain, LlamaIndex, and GPT4All
- Surpassed 1 million developer users and 1,400+ enterprise organizations
- 30+ foundation model builders use W&B for training and evaluation
- Certified as NVIDIA DGX-Ready Software and NVIDIA AI Enterprise partner
- W&B Weave reached GA for enterprises in December 2024
- W&B GitHub repository surpassed 10,900+ stars
- Hosts 'Fully Connected' global AI conference with 750+ engineers per event

## Latest updates

- **2026-01** — W&B Server v0.77 released with security enhancements to API keys and GA of media panel sync and looping features.
- **2025-11** — Fully Connected Conference London 2025 hosted 750+ AI engineers (Nov 4–5, 2025).
- **2025-06** — CoreWeave and W&B announced three new AI cloud products in preview: Mission Control (infrastructure observability), W&B Inference, and W&B Weave Online Evaluations.
- **2025-05** — CoreWeave completed acquisition of Weights & Biases for ~$1.7B on May 5, 2025.
- **2025-03** — CoreWeave announced acquisition of Weights & Biases (March 4, 2025). W&B Weave became available on AWS Marketplace in the new 'AI Agents and Tools' category.
- **2024-12** — W&B Weave reached General Availability (GA) for Enterprises with full tracing, evaluations, monitoring, and guardrails suite.
- **2024-11** — Expanded Microsoft integration: new W&B Models integration with Azure AI Foundry for fine-tuning GPT-4 and GPT-4o with automatic experiment tracking.
- **2024-03** — Announced NVIDIA platform integrations — W&B certified as NVIDIA DGX-Ready Software and NVIDIA AI Enterprise partner, with NIM microservices and DGX system integrations.

## Links

- Website: https://wandb.ai
- LinkedIn: https://www.linkedin.com/company/wandb
- Twitter/X: https://x.com/weights_biases
- GitHub: https://github.com/wandb
- YouTube: https://www.youtube.com/@weights_biases

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Published by YesPress — https://yespress.io
Last updated: 2026-04-03