Lukas Biewald

Lukas Biewald is co-founder of Weights & Biases, the AI developer platform that CoreWeave acquired in 2025. Before that he founded CrowdFlower, one of the first companies to sell training data for machine learning.

Playing Othello Against a Machine at Stanford

"I remember the magic I felt training my first machine learning algorithm," Biewald wrote on his blog. In 2002, taking Daphne Koller's class at Stanford, he spent 72 hours straight in the computer lab building a reinforcement learning program that played Othello against itself until it beat him. He earned a master's degree in computer science at Stanford's AI lab, according to Insight Partners.

Selling Training Data Before Investors Wanted AI

By 2007, he wrote, access to training data was the biggest problem in machine learning, so he left his job to start CrowdFlower. "I remember in my first decks being advised to remove any mention of AI from the pitch deck," he told Unusual Ventures. He ran the company for more than a decade, renamed it Figure Eight, and sold it to Appen in March 2019 for $300 million.

Building Experiment Tracking in a Rented Airbnb

In 2018 he founded Weights & Biases with his CrowdFlower co-founder Chris Van Pelt and Google engineer Shawn Lewis. They built their first product, experiment tracking, in an Airbnb rented for a hack day. CoreWeave completed its acquisition of the company on May 5, 2025, according to CoreWeave's announcement.