24 May 2007
About 60 million CAPTCHAs are solved by humans around the world every day. In each case, roughly ten seconds of human time are being spent. Individually, that’s not a lot of time, but in aggregate these little puzzles consume more than 150,000 hours of work each day. What if we could make positive use of this human effort? reCAPTCHA does exactly that by channeling the effort spent solving CAPTCHAs online into “reading” books.
Brilliant idea: reCAPTCHA mashes up the shortcomings of OCR software when digitizing books and the shortcomings of the web when fighting bots and spam. It extracts value from CAPTCHA systems by sending 2 distorted words: one of them not read correctly by the OCR tool, the other one already known. If the user has the known one right it is assumed the other one is right too.