May 24, 2007
You’ve all seen CAPTCHAs before, where a form requires additional input from the user to protect itself from automated spam. Here’s a new project from Carnegie Mellon, made by Ben Maurer:
You might notice that reCAPTCHA has two words. Why? reCAPTCHA is more than a CAPTCHA, it also helps to digitize old books. One of the words in reCAPTCHA is a word that the computer knows what it is, much like a normal CAPTCHA. However, the other word is a word that the computer can't read. When you solve a reCAPTCHA, we not only check that you are a human, but use the result on the other word to help read the book!
This is a great idea in my opinion; it finds a use for what would otherwise be wasted effort, and turns it into something useful. Accessibility (which has always been a big problem for CAPTCHAs) seems to be taken into account here as well.
Another good one is on the ridiculous fish blog, which uses a homemade CAPTCHA to calculate pi.