Snorkel AI raises $350M at $3.5B valuation as AI data demand surges

Snorkel AI, an AI data services company, announced on September 23 that it has raised $350 million in a Series E round at a $3.5 billion valuation, nearly triple the $1.3 billion valuation from its Series D round in April 2025. Insight Partners and S32 led the round, with participation from existing investors including Addition, Lightspeed, Greylock, GV, and Wells Fargo.

The seven-year-old startup initially offered data labeling automation software. In 2025, it shifted to delivering completed datasets and simulated environments to customers, a model it calls data-as-a-service. Instead of operating purely as a marketplace for human experts, Snorkel combines its software and models to generate data synthetically alongside input from subject matter experts.

The company said its annualized revenue run-rate has reached $375 million, an 18-fold increase over the past 12 months, driven by AI labs' strong demand for high-end training data. Other AI data companies have seen similar growth: Mercor's gross annualized revenue has climbed to $2 billion, Handshake surpassed $1 billion, and Micro1 reached $500 million. However, Snorkel noted that those companies typically pay out 60-70% of revenue to domain specialists, making their net revenue substantially lower.

Snorkel sells reinforcement learning environments and complete datasets rather than human labor, so payments to its human experts are recorded in cost of goods sold rather than in headline revenue figures. The company launched commercially in 2019 after four years of research by co-founder and CEO Alex Ratner and his team at a Stanford AI lab.