Roughly 200 million CAPTCHAs are completed every day, taking around 2000 million seconds or 33,333 hours of human time. reCAPTCHA was created by Luis von Ahn to provide a free service that protects websites from spam and abuse using risk analysis and adaptive CAPTCHAs, while allowing valid human users to pass through easily. It aims to be tough on bots but easy on humans, and also offers audio CAPTCHAs for visually impaired users.