Prolific

Prolific occupies a specific and well-earned niche: recruiting real, pre-screened human participants for online research — surveys, experiments, interviews, and longitudinal studies. Its reputation in academic and UX research circles rests on participant quality. Because participants are vetted, fairly paid, and can be filtered against hundreds of demographic criteria, the data tends to be markedly cleaner than what you'd get from cheaper crowdwork platforms like Mechanical Turk, where bots and low-effort responses are a chronic problem. Pricing is transparent and pay-as-you-go: you set the per-participant reward (Prolific enforces an ethical pay minimum) plus a platform fee on top, with no subscription. That makes costs predictable but not cheap — quality is the trade you're paying for. The honest caveats: the fair-pay model plus platform fee makes large samples genuinely expensive, the participant pool skews toward certain regions and demographics (UK and US heavy), and very niche targeting can be slow to fill. For researchers who need trustworthy human data and can't risk a sample full of bots, though, Prolific is close to the default choice, and its granular screening and API make it practical for serious study design.