Provide a text alternative describing the purpose of the CAPTCHA
Make sure CAPTCHAs have text alternatives that describe their purpose
CAPTCHAs, by their very nature, raise many accessibility concerns for most users out there, including people with various disabilities. From the perspective of non-sighted screen reader users, the most important issue CAPTCHAs raise is unquestionably the fact that the ALT text value of such images cannot possibly describe what the image represents without giving the test away. Still, as informative images, CAPTCHAs need to convey meaningful information to assistive technologies. Consequently, authors need to make them accessible to users who cannot see them.
To do so, simply make sure the ALT text value of the CAPTCHA image properly describes its purpose. As CAPTCHA images are meant to tell computers and humans apart, providing the answer to the test inside the ALT value of the image would automatically beat the purpose and give computers the answer only humans are supposed to provide. Therefore, the first thing authors need to do to address the accessibility of CAPTCHA images – or lack thereof – is to use the value of the ALT attribute of the image to indicate what the image is used for. Doing [...]