Understandability

The quality of information or interface elements being cognitively accessible — meaning a user can not only perceive the content but also internalise its meaning and know how to act on it. Understandability is one of the four principles of WCAG 2.0, requiring that information and the operation of user interfaces be understandable. It encompasses readable text, predictable page behaviour, and input assistance. Research has shown that evaluating understandability separately from perceivability identifies significantly more accessibility problems, particularly cognitive barriers that affect users with intellectual disabilities, learning disabilities, or limited domain knowledge.