reCAPTCHA: The 200 Million Daily Free Labor Scheme

A 5-minute explainer on reCAPTCHA — how Luis von Ahn turned 200 million daily CAPTCHA solves into free labour that digitised the New York Times archive and Google Books. The two-word trick (one known, one unknown), the 2018 shift to invisible scoring, and what v3 actually measures about you. Diagram the pipeline; end on the irony of AI now solving them better than humans.