CAPTCHA

Wikipedia's ReCAPTCHA test, used before making certain changes or creating accounts. The letters are completely random.

A CAPTCHA is a test that is used to separate humans and machines. CAPTCHA stands for "Completely Automated Public Turing test to tell Computers and Humans Apart." It is normally an image test or a simple mathematics problem which a human can read or solve, but a computer cannot. It is made to stop computer hackers from using a program to automatically set up hundreds of accounts, such as email accounts. It is named after mathematician Alan Turing's Turing test.

CAPTCHA Media

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  This CAPTCHA (Version 1Template:Clarifyme) of "smwm" obscures its message from computer interpretation by twisting the letters and adding a slight background color gradient.

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  Many websites require typing a CAPTCHA when creating an account to prevent spam.

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  An example of a reCAPTCHA challenge from 2007, containing the words "following finding". The waviness and horizontal stroke were added to increase the difficulty of breaking the CAPTCHA with a computer program.

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  A CAPTCHA usually has a text box directly underneath where the user should fill out the text that they see. In this case, "sclt ..was here".