Mercor runs a two-sided marketplace that sits between human domain expertise and AI model development. On one side, it recruits and vets millions of credentialed professionals — doctors, lawyers, engineers, scientists — using AI-driven screening and interviews. On the other side, it sells their work to AI labs (OpenAI, Anthropic) and Fortune 500 companies as RLHF training data, model evaluations, and expert demonstrations. Contractors are paid on demand to answer questions, rate model outputs, and produce specialized training datasets. Mercor also operates APEX, a benchmark family measuring AI's real-world performance on professional tasks. Its Enterprise division packages this same infrastructure for large companies, helping them capture how their best people work and translate that into custom AI. The July 2026 acquisition of Deeptune adds reinforcement learning environments for agent training. Mercor was founded in 2023 by three Thiel Fellows; it pays out over $4M per day to contractors and crossed $2B in annualized gross revenue by June 2026.