After inventing Captchas — that familiar fraud prevention system in which Internet users are shown some wavy numbers and letters and have to type them into a box to prove they are not automated bots — Luis von Ahn realized something dismal: It takes about 10 seconds to fill out one of these boxes, and people complete about 200 million of them a year — a waste of hundreds of thousands of hours.
So he invented Recaptcha — in which people instead are shown a small fragment of an old book to type in, putting those 10 seconds to work helping to digitize those texts. Same fraud prevention, more productive.
And if people could help digitize books, maybe they could help translate websites, too, he thought. So von Ahn’s Duolingo lets language learners supplement their data-driven instruction by translating websites like CNN. CNN writes its news in English, sends it to Duolingo, and then the company sends it to users as practice. Von Ahn explains in this video:
This article originally appeared on Recode.net.