Snorkel AI raises $350M Series E at $3.5B valuation to expand data-as-a-service for AI training

Snorkel AI, a seven-year-old startup, raised a $350 million Series E at a $3.5 billion valuation, led by Insight Partners and S32. Existing investors including Addition, Lightspeed, Greylock, GV, and Wells Fargo also participated. The valuation nearly triples the $1.3 billion figure from its April 2025 Series D, which raised $100 million.

The company’s annualized revenue run rate reached $375 million, an eighteenfold increase over the prior 12 months. Snorkel attributes this growth to demand from AI labs and corporations for high-quality training data, which it supplies via a data-as-a-service model.

Snorkel originally focused on software for data-labeling automation but shifted last year to providing completed datasets. Its hybrid approach combines synthetic data generation using software and models with contributions from subject matter experts. The company launched commercially in 2019 after four years of research at a Stanford AI lab led by co-founder and CEO Alex Ratner.

Snorkel’s revenue model differs from competitors that rely on human labor marketplaces. While companies like Mercor, Handshake, and Micro1 pay 60% to 70% of top-line income to domain specialists, Snorkel accounts for payments to human experts as cost of goods sold rather than headline revenue. This reflects its focus on selling reinforcement learning environments and complete datasets rather than human labor.