accessibility

Accessibility refers to designing products, services, and environments to be usable by people with disabilities or diverse abilities. It aims to remove barriers that impede participation in everyday life. While it applies to physical spaces, accessibility also covers information and communication technologies, education, transportation, and public services. In digital contexts, it means content usable by people with visual, auditory, motor, or cognitive impairments, including text alternatives, captions, keyboard navigation, clear layout, and assistive-technology compatibility.

The Web Content Accessibility Guidelines (WCAG) define four principles for web content—perceivable, operable, understandable, and robust (the POUR framework)—with success criteria at multiple conformance levels (A, AA, sometimes AAA). Related standards include ATAG for authoring tools and UAAG for user agents.

A growing body of laws and policies requires accessible information and services. In the United States, the ADA and the Rehabilitation Act influence digital access; in the European Union, the accessibility directive governs public sector websites and apps; other jurisdictions have equivalent provisions.

Organizations pursue inclusive design or universal design to anticipate diverse user needs. Practical measures include semantic markup, alternative text for images, captions and transcripts, sufficient color contrast, keyboard operability, responsive design, and accessible error handling. Accessibility is evaluated through user testing with people with disabilities, automated checks, and manual reviews.

Besides facilitating inclusion, accessible design improves usability for all users, supports assistive technology, and can enhance search engine optimization and device independence.