Accessibility testing
Accessibility testing is a software quality assurance discipline that verifies a system can be used by people with the widest possible range of abilities. It checks that interfaces work with assistive technologies and conform to published accessibility standards, so that people with visual, motor, cognitive, or auditory impairments are not excluded from using the software.
Unlike usability testing, which examines how easily any user can accomplish a task, accessibility testing focuses specifically on barriers that affect users with disabilities. The two overlap – an inaccessible interface is unusable for the people it excludes – but accessibility testing is judged against defined standards rather than subjective ease of use.
Standards and guidelines
Accessibility testing is typically measured against formal standards rather than ad hoc judgment. The most widely cited is the Web Content Accessibility Guidelines (WCAG), published by the W3C. WCAG defines success criteria at three conformance levels – A, AA, and AAA – organized around four principles: content must be perceivable, operable, understandable, and robust. Other frameworks include Section 508 in the United States and the European Accessibility Act in the EU, many of which reference or align with WCAG.
Because conformance to these standards is often a legal or contractual compliance requirement, accessibility testing frequently overlaps with compliance testing.
Methods
Accessibility testing combines automated and manual techniques, because no single approach catches every defect.
Automated tools scan for mechanical violations – missing alternative text, insufficient color contrast, duplicate or missing heading levels – and can run on every commit as part of automated testing. They catch a large share of defects quickly but miss issues that require human judgment, such as whether alternative text meaningfully describes an image.
Manual review fills that gap. Testers navigate the interface with a keyboard alone, inspect the page with screen readers such as NVDA or VoiceOver, and verify that focus order and live regions behave as expected. Testing with real users who rely on assistive technology is the most reliable way to surface barriers that neither automated scans nor expert review uncover.
Note
Automated tools typically detect only a minority of WCAG success criteria definitively. Passing an automated scan is not the same as passing an accessibility audit.
Relationship to non-functional requirements
Accessibility is one of the non-functional requirements a system may be expected to meet. Like other quality attributes, it is easiest to achieve when considered early in design and expensive to retrofit, because inaccessible patterns are often woven through markup, component libraries, and visual design.