Snorkel AI triples valuation to $3.5B with $350M Series E funding

Snorkel AI just closed a $350 million Series E that values the company at $3.5 billion, nearly tripling its previous $1.3 billion valuation from just over a year ago. The round, announced on September 22, cements the Stanford-born startup as one of the hottest names in AI infrastructure, a category that has quietly become the picks-and-shovels play of the generative AI gold rush. What makes this valuation jump particularly striking is the revenue story behind it. Snorkel AI’s annualized revenue run-rate has ballooned from roughly $20 million a year ago to somewhere between $350 million and $375 million today. That’s over 17x growth in twelve months. From research project to revenue machine Snorkel AI was founded in 2019 by researchers from the Stanford AI Lab, including CEO Alex Ratner. For most of its life, the company operated as a software platform helping organizations label and curate training data for machine learning models. The inflection point came in September 2025, when the company launched its data-as-a-service offering. Instead of selling tools for clients to build their own datasets, Snorkel started delivering ready-to-use, specialized training datasets and reinforcem...