CAPTCHA is testing software used by many websites to cut down on online fraud. Sites often use CAPTCHA systems to make sure that new accounts are created by human beings, instead of automated scripts. Typically a CAPTCHA test presents a hard-to-read image of a word, which the user must then type in to prove he is not a machine. The audio version gives visually impaired users a way to use CAPTCHA, by playing a recorded sound of the test word.
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