accessibility

Accessibility (often abbreviated a11y) in web design means ensuring that people with disabilities can perceive, understand, navigate, and interact with web content. The term encompasses a wide range of conditions — visual, auditory, motor, cognitive, neurological — and a corresponding range of assistive technologies: screen readers, magnifiers, voice control, switch devices, Braille displays.

Accessibility is grounded in the social model of disability, which locates the barrier not in the person but in the environment. A website that requires a mouse to operate disables anyone who cannot use a mouse. A video without captions disables anyone who cannot hear. The problem is in the design, not in the user.

The primary standard for web accessibility is the Web Content Accessibility Guidelines (WCAG), published by the W3C’s Web Accessibility Initiative. WCAG organizes requirements around four principles: content must be perceivable, operable, understandable, and robust (POUR).

Accessibility also overlaps with Universal Design — the principle, originating in architecture, that designing for the widest range of users from the start produces better outcomes for everyone [@mace_AccessibleEnvironments_1991].