What is a CAPTCHA?
( 03:40 )
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VIDEO DESCRIPTION:

We've all run into CAPTCHAs: those sometimes annoying, sometimes hard to decipher strings of characters and numbers that appear online. They have to be punched in exactly as they appear when signing up for a free email account, posting a comment in a public forum and so on. But what are they and what purpose do they serve? Stacy Reed explains.

+ ADD TO MY LIST
- REMOVE FROM MY LIST
+ ADD TO MY LIST
- REMOVE FROM MY LIST
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By signing up, you can access your watch list and history across your other devices including mobile, tablet and Connected TV.
You can

It only takes a few seconds!