Techniques for WCAG 2.0

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G143: Providing a text alternative that describes the purpose of the CAPTCHA


Applies to all technologies.

This technique relates to:


The purpose of this technique is to provide information via the text alternative that identifies the non-text content as a CAPTCHA. Such tests often involve asking the user to type in text that is presented in an obscured image or audio file. From the text alternative, the user can tell that the CAPTCHA requires completing a task and what type of task it is.

When an alternate version of a CAPTCHA is available, the text alternative should include instructions about how to find the alternate version.




  1. Remove, hide, or mask the CAPTCHA.

  2. Replace it with the text alternative.

  3. Check that the text alternative describes the purpose of the CAPTCHA.

Expected Results

If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.

Techniques are Informative

Techniques are informative—that means they are not required. The basis for determining conformance to WCAG 2.0 is the success criteria from the WCAG 2.0 standard—not the techniques. For important information about techniques, please see the Understanding Techniques for WCAG Success Criteria section of Understanding WCAG 2.0.