Snorkel AI Raises $350M Series E, Valued at $3.5B

Snorkel AI has successfully closed a substantial $350 million Series E funding round, propelling its valuation to an impressive $3.5 billion. This significant capital infusion nearly triples the company's previous valuation from just 17 months prior, underscoring its rapid ascent in the critical AI training data sector. The round was co-led by prominent venture capital firms Insight Partners and S32, with robust participation from existing investor Addition. A strong cohort of new investors also joined, including March Capital, Blumberg Capital, Allegis Capital, Frontline, Standard, and Third Point Ventures. Further backing came from a slate of returning investors: Greylock, Lightspeed, GV, Factory, Prosperity7, Walden Catalyst, and Wells Fargo.

Emerging from the esteemed Stanford AI Lab in 2019, Snorkel AI has distinguished itself by pioneering "weak supervision" techniques. This methodology allows for the refinement of large-scale datasets without the prohibitive cost and time of manual human labeling for every data point. The company's innovative approach has fostered a significant academic following, with over 250 research papers stemming from this work, accumulating more than 25,000 citations. This deep research foundation is now translating into significant commercial traction.

Since pivoting to an expert-driven "data-as-a-service" model in September 2025, Snorkel AI has experienced explosive growth. The company reports an eighteenfold increase in its annualized revenue run rate over the past year, reaching $375 million. This metric reflects a business model focused on delivering finished datasets and complex evaluation environments directly to leading AI laboratories and enterprises, differentiating it from marketplace-style competitors where gross transaction volume is often highlighted.

CEO Alex Ratner, who led the original open-source Snorkel project as a PhD student, emphasized the company's role as a research partner for cutting-edge AI development. \"The teams pushing the frontier want a research data partner who pioneers the science of data development,\" Ratner stated. \"That’s what Snorkel was built to be: the frontier lab for agentic data, combining human excellence with over a decade of research and technology.\" This focus on high-quality, complex data solutions addresses the evolving needs of advanced AI systems, particularly agentic and frontier models.

The newly acquired capital will be strategically deployed to expand the capacity of Snorkel AI's agentic data factory, accelerate investments in vertical and enterprise AI solutions, and broaden its research into new domains and data modalities. The company also plans to deepen its commitment to open research initiatives, such as its Open Benchmarks Grants program, further solidifying its position as an innovator in the field.

This funding round occurs amidst a dynamic and rapidly consolidating AI training data market. Competitors like Scale AI have seen shifts in their operational models, prompting major AI players to seek neutral data partners. Other companies, such as Mercor and Handshake, have achieved significant scale, though their reported revenue figures often reflect marketplace throughput. Surge AI, operating with significant revenue without external funding, also represents a formidable presence. Snorkel AI's unique value proposition lies in its research-backed, hybrid approach, synthesizing subject-matter expertise with proprietary software and models to generate high-fidelity data.

Lonne Jaffe of Insight Partners highlighted Snorkel's "research-grade approach to AI data, environments, and measurement" as a crucial element for building capable AI systems. Similarly, Andy Harrison from S32 noted the "expert-agentic environments" create a powerful synergy, enabling data delivery at the speed and quality required for the next generation of AI model development.