Four platforms, four different models — here's how they actually differ.
Mercor, Turing, Prolific, and Alignerr all connect people with paid AI-training and evaluation work, but they're not interchangeable — each one is built around a different relationship with its clients and a different kind of task. Knowing the difference matters more than picking a "best" one, since the right platform depends on what kind of work you're actually looking for.
Mercor is a hiring platform that matches vetted professionals — engineers, doctors, lawyers, writers, and more — directly with AI labs and companies that need expert human judgment. Most roles involve interviewing, evaluating, or producing high-quality human data used to train and improve AI models. Its vetting leans on real professional credentials, which is why its roles skew toward people with a specific, verifiable background rather than generalist annotation work.
Turing positions itself as a research accelerator working directly with frontier AI labs and enterprises, connecting engineers, researchers, and domain experts with paid project work spanning coding, reasoning, multilinguality, and more. It leans technical — a large share of its roles assume real engineering or research depth, not just careful judgment.
Prolific runs a participant-research model: AI labs and researchers draw on a global pool of participants for paid training and evaluation tasks, most of it priced per task rather than hourly. Its "Participant Recruitment" roles span dozens of domains and languages, and the barrier to entry is generally lower than Mercor or Turing — it's built for volume and breadth of participation, not a narrow vetted specialist pool.
Alignerr, powered by Labelbox, runs an expert marketplace for task authoring and grading — writing and evaluating tasks used to train and align frontier models, spanning marketing, sales, coding, STEM, audio, and more. Most roles are hourly and fully remote, sitting somewhere between Mercor's credential-heavy vetting and Prolific's broader participant pool.
Pay, task type, and eligibility all shift constantly as new work comes in on each platform, so a static ranking would be stale within weeks. The more reliable approach: see what's currently open on each platform here, or browse every open role by pay range to see where each platform's live postings actually land right now.