ReCAPTCHA puts a new spin on the typical ‘Completely Automated Public Turing test to tell Computers and Humans Apart’ (CAPTCHA)
CAPTCHA describes a technique for restricting website access to spammers or bots by means of an image with scrambled letters that a human user should be able to recognize and authenticate. ReCAPTCHA combines a solution to this common problem with the ability to help scan and make digitally available the vast wealth of print media information in circulation.
How it works: Users are shown a background image with two words printed over it. One of these words is already known and understood by the computer but the other is one that it was unable to recognize when scanned off the page. The user then types in these words and is granted access if the response was correct. ReCAPTCHA benefits from providing the service because each time someone verifies him or herself this way, another previously unrecognized word is added to the project’s version of that text.