CAPTCHA
This term is defined by more than one standard, and the wording differs. Each definition below is the one that applies to that standard’s criteria.
Definition in RAWeb 1.1
A CAPTCHA is a test used to distinguish a human user from a computer. The test often uses images containing distorted text, mixed with other shapes or using altered colour schemes, which the user is asked to retype. Other forms of CAPTCHA may be based on logical questions or sound clips.
Criteria in RAWeb 1.1
Definition in RAAM 1.1
A CAPTCHA is a test used to distinguish a human user from a computer. The test often uses graphic elements containing distorted text, mixed with other shapes or using altered colour schemes, which the user is asked to retype. Other forms of CAPTCHA may be based on logical questions or sound clips.
W3C provides full documentation on the accessibility of this type of test: Inaccessibility of CAPTCHA.