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See also: captcha and Captcha


A typical representation of a CAPTCHA

Alternative forms[edit]


Coined by a team of researchers at Carnegie Mellon University in 2000 as a loose acronym of “Completely Automated Public Turing test to tell Computers and Humans Apart”.




  1. A computerized test requiring the human user to perform a task deemed to be difficult to automate, such as entering a displayed series of distorted characters or describing images, to demonstrate that he/she is a human and not a computer program.
    • 2011, Dafydd Stuttard, Marcus Pinto, The Web Application Hacker's Handbook: Finding and Exploiting Security Flaws, John Wiley & Sons (→ISBN)
      CAPTCHA puzzles are intended to be easy for a human to solve but difficult for a computer. Because of the monetary value to spammers of circumventing these controls, an arms race has occurred in which typical CAPTCHA puzzles have []
    • 2014, Laura Fitton, Anum Hussain, Brittany Leaning, Twitter For Dummies, John Wiley & Sons (→ISBN), page 24:
      A CAPTCHA is a quick check to make sure that an actual person, rather than a computer program, is using the website. Web applications use CAPTCHA []

Derived terms[edit]

Usage notes[edit]

Although occasionally spelt with lowercase letters (captcha), or with an initial uppercase letter (Captcha), most authors remain aware of its origin as an acronym and use uppercase. This is not always the case for other languages. For example, the Dutch language has adopted the word from English, but only in its acronym form. Thus in Dutch it is spelled with lowercase letters.


See also[edit]

Further reading[edit]



Borrowed from English.


CAPTCHA m (plural CAPTCHA's)

  1. Alternative letter-case form of captcha