CAPTCHA and reCAPTCHA are developed to protect websites from machine generated attacks called bots. There is practically no difference between CAPTCHA and reCAPTCHA. Their sole objective is to ensure that machine don’t use what is meant for human – like posting comments, registration to a website etc. The difference lies in objective, working behind the scene and security.
Reduce human workload
The biggest objective behind the development of reCAPTCHA is to reduce workload of human and make the system entirely automated. Previously, CAPCHTA image texts available to websites were written by humans. This human written text is then distorted by adding whirls, warps and meshes to make sure no machine reads it. About 200 millions CAPTCHAs are written each day which consumes 150,000 hours. Hell lot of time I would say!
Stop Spam, Read Books
In reCAPTCHA, all the texts are taken from the old editions of The New York Times and Google books which are not readable to OCR (Optical Character Recognition). Words that aren’t recognized by character recognition software were distorted slightly and converted to CAPTCHAs. These texts are showed in CAPTCHA/reCAPTCHA block to users to decipher. That’s why tagline of reCAPTCHAS says ‘Stop Spam, Read Books’.
Stronger security than CAPTCHA
The other difference between CAPTCHA and reCAPTCHA lies in the security. CAPTCHAs are vulnerable to hacks either by removing background clutter and noise or by identifying the character in each region. When spammers tested the same techniques against images created using reCAPTCHA – they failed completely. There was huge difference in the Mathematical transformation in CAPTCHA and reCAPTCHA texts. We can’t say that reCAPTCHAs are unbeatable but the success rate is as low as 10%.