CAPTCHA stands for Completely Automated Public Turing Test to tell Computers and Humans Apart. CAPTCHA is essentially a simple test that verifies that human website users are not malicious bots intent on enacting fraud and abuse on a site. Google has its own version of CAPTCHA, which is called reCAPTCHA. reCAPTCHA is a free service that uses an advanced risk analysis engine and adaptive CAPTCHAs to protect websites from abusive automated software.