The IT Law Wiki


CAPTCHA is a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart."

It is

a computer security program . . . that is designed to distinguish between human users and computer programs, and thereby prevent purchasers from using automated devices to purchase tickets.[1]
a challenge-response test to determine if a user is a human. CAPTCHA tests are often based on visual-perception tasks, such as reading distorted text or selecting a particular image, but they can also be audio based. Newer versions incorporate additional features, since researchers and malicious actors have created multiple methods to defeat the visual and audio tests. On the Internet, CAPTCHA is used to protect website forms and other services from abusive traffic, mostly generated by bots, including credential reuse attacks, email bombs, and inappropriate comments on discussion boards.[2]


CAPTCHAs present a user with a challenge, usually to correctly type in a series of letters and/or numbers, to prove that the user is not a bot. Google offers a CAPTCHA option for its Gmail application that requires users to answer basic math questions in order to send an email. The Gmail CAPTCHA feature is called “Mail Goggles,” a reference to “beer goggles,” and is designed not to prevent bots from sending messages but to prevent users from sending emails while intoxicated.

"[S]ome CAPTCHA techniques, which can be implemented as an obscured word in an image, do not comply with American Disability Association (ADA) or Section 508 accessibility guidelines."[3]


"[B]ecause CAPTCHA 'in the ordinary course of its operation, requires the application of information . . . to gain access to the work,' it is a technological measure that regulates access to a copyrighted work."[4]


  1. Ticketmaster L.L.C. v. RMG Technologies, Inc., 507 F.Supp.2d 1096, 1102 (C.D. Cal. 2007) (full-text).
  2. Center for Internet Security, EI-ISAC Cybersecurity Spotlight – CAPTCHA (full-text).
  3. NIST Special Publication 800-44, at 5-8.
  4. 507 F.Supp.2d at 1112.

External resources[]

  • Information on CAPTCHA tests is available here.