Abhinav Sharma

ReCaptcha is Carnegie Mellon startup that I’ve seen a lot of recently on blogs. I was wondering what the deal is and what makes it different from other Captchas. It turns out that recaptchas use two words instead of one. One of them is a recognized word, while the other is not, what you enter in the latter field helps digitize books.

Smart thinking indeed. I couldn’t find any documentation on how exactly it works, but I’m guessing it uses a probabilistic method based on what the majority of people type in. Sometimes, its easy to guess which word is likely to be the unrecognized word, so it becomes easier to screw around. Moreover, what would happen if the unrecognized word is likely to be confused with another word, there might be trouble with probabilistic methods then?

Considering that, its probably a good thing not many who enter a reCaptcha dont know how it works, or they would probably be too lazy to get the second word right.