Artificial Intelligence · Profile from AI Research Companion
Weights & Biases
The San Francisco developer-tools company, founded in 2017 by Lukas Biewald, Chris Van Pelt and Shawn Lewis, whose experiment-tracking software became the default "lab notebook" for deep-learning research, including at OpenAI and most other frontier labs (company claims). Weights & Biases (W&B) sold to the people who train models rather than to the people who use them: a free tier for researchers and academics, then paid team and enterprise licences, including self-hosted deployments. It raised ~$250m (reported) at valuations that reached $1.25bn (August 2023), tried to follow its users from model training into large-language-model applications with W&B Prompts (2023) and Weave (2024), and in 2025 sold itself to the GPU cloud CoreWeave for a reported ~$1.7bn (agreed March 2025, completed May 2025; CoreWeave did not disclose a price). By late 2026 W&B is a product line inside CoreWeave's software platform, still sold to customers on other clouds, and its story is the clearest case in this knowledge base of a beloved, standard-setting MLOps tool whose best exit was to a compute supplier.
At a glance
- Founded
- 2017, San Francisco, by Lukas Biewald (CEO), Chris Van Pelt and Shawn Lewis; Biewald and Van Pelt had earlier co-founded the data-labelling company CrowdFlower (later Figure Eight, sold to Appen in 2019)
- Headquarters
- San Francisco, with staff in the US, Europe and Asia (reported)
- Ownership / structure
- Private until May 2025; since then a wholly owned subsidiary and product line of CoreWeave, Inc. (Nasdaq: CRWV), described as "a CoreWeave company" and part of CoreWeave's software offering (company, 2025–26)
- Leadership (2026)
- Lukas Biewald (co-founder; described in CoreWeave-era materials as general manager of W&B — verify title); Chris Van Pelt and Shawn Lewis (co-founders; one 2026 profile lists Lewis with a broader CoreWeave role, verify); CoreWeave management (Michael Intrator, CEO) above them
- AI products
- W&B Models (experiment tracking, Sweeps hyperparameter search, Artifacts versioning, Tables, Reports, Registry, Launch); W&B Prompts (2023); W&B Weave (LLM tracing, evaluation and monitoring, launched April 2024; enterprise general availability later); W&B Inference (open-model inference on CoreWeave GPUs, preview June 2025); integrations with CoreWeave Mission Control and OpenPipe's reinforcement-learning tools (2025)
- Scale
- >1m users and most frontier labs as customers (company claims at the time of the CoreWeave deal, reported); customers named by the company over time include OpenAI, Nvidia, Toyota Research Institute and others (company, verify list); revenue never disclosed
- Capital raised
- ~$5m Series A co-led by Bloomberg Beta and Trinity Ventures (May 2018, reported); ~$15m (2019, reported, verify); $45m Series B led by Insight Partners (February 2021); $135m Series C co-led by Felicis and Bond at ~$1bn (October 2021); $50m led by Daniel Gross and Nat Friedman at $1.25bn (August 2023); total ~$250m (reported; some sources say ~$150m+)
- Exit
- Acquired by CoreWeave: agreed March 2025, completed May 2025 (May 5–8, sources differ); ~$1.7bn reported, not disclosed by CoreWeave
- Signature moves (incl. failures)
- Founding after Figure Eight (2017); free for researchers and the OpenAI adoption (2018–20); Series B and C and the unicorn valuation (2021); W&B Prompts and the Gross–Friedman round (2023); Weave and the crowded LLMOps market (2024, mixed); the CoreWeave acquisition (2025); W&B Inference and the neutrality test (2025–26)
7 strategic moves analysed
Each one gets a full strategy file in the companion: context, the decision, the financing, what happened, and the lesson.
2017
Founding After Figure Eight
Founding
2018
Free for Researchers and the OpenAI Adoption
Launch / go-to-market
2021
Series B and C and the Unicorn Valuation
Funding round
2023
Prompts and the Gross Friedman Round
Launch / funding round
2024
Weave and the Crowded LLMOps Market
Launch / pivot (mixed result)
2025
CoreWeave Acquisition
Acquisition (target)
2025
W and B Inference and the Neutrality Test
Launch / integration