What is a CAPTCHA?

A CAPTCHA (Completely Automated Public Turing Test To Tell Computers and Humans Apart) is a type of challenge-response test used to determine whether or not the user is a human being. Commonly, CAPTCHAs require you to type letters of a distorted sequence that appear on your computer screen.

Since humans can read and type such distorted text but current computer programs cannot, CAPTCHAs help prevent bot programs from using different types of computing services, such as responding to a poll or registering for a product.

Not all CAPTCHAs are visual; some use other means (e.g., speech recognition).

The information in this document came from Wikipedia and the The Official CAPTCHA Site.

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