recaptcha is a gem that uses google's CAPTCHA service. A CAPTCHA is a program that can tell whether its user is a human or a computer. To Setup recaptcha on local machine we need to add the gem, gem "recaptcha", :require => "recaptcha/rails" then we need to obtain private and public key by registering to this url http://www.google.com/recaptcha/whyrecaptcha While registration we can choose if we need public and private keys which work on particular domain or we can choose to use it on any domain. Once we have the public and private key we can