What are some amazing facts about Google or Microsoft?
The Google reCAPTCHA Project
reCAPTCHA improves the process of digitizing books by sending words that cannot be read by computers to the Web in the form of CAPTCHAs for humans to decipher. More specifically, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA. This is possible because most OCR programs alert you when a word cannot be read correctly and this also ensures that the image is unreadable by machines.
But if a computer can't read such a CAPTCHA, how does the system know the correct answer to the puzzle? Here's how: Each new word that cannot be read correctly by OCR is given to a user in conjunction with another word for which the answer is already known. The user is then asked to read both words. If they solve the one for which the answer is known, the system assumes their answer is correct for the new one. The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct.
The system has been reported as displaying over 100 million CAPTCHAs every day, and among its subscribers are such popular sites as Facebook, TicketMaster, Twitter, 4chan,, Craigslist, and StumbleUpon. The Google reCAPTCHA project is astonishingly elegant and amazingly simple!
The reCAPTCHA was originally created by , Ben Maurer, Colin McMillen, David Abraham and . Google acquired it on September 16, 2009 for $27 million. Thanks to Aniruddha for pointing it out in the comments.
Sometimes you wonder if they should have kept the entire project details a secret, though Google issued a statement saying that any such attack to misuse the reCAPTCHA project would require much greater numbers.