Web Content Accessibility Guidelines
The Web Content Accessibility Guidelines (WCAG) are the global standard for web accessibility. Developed by the World Wide Web Consortium (W3C) in collaboration with individuals and organisations worldwide, they provide a shared set of technical standards for making web content accessible to people with a wide range of disabilities — visual, auditory, physical, cognitive, and neurological.
While WCAG itself isn't a law, it's the benchmark for accessibility — and following these guidelines is the best way to comply with accessibility legislation like the Americans with Disabilities Act (ADA) or the European Accessibility Act.
The four principles of accessibility (POUR)
WCAG is organised around four fundamental principles, known by the acronym POUR. For content to be accessible, it must be:
| Principle | Meaning |
|---|---|
| Perceivable | Users must be able to perceive the information presented. Images need text alternatives for screen readers, and audio content needs captions for users who are hard of hearing. |
| Operable | Users must be able to operate the interface. All functionality should be available from a keyboard for users who can't use a mouse. |
| Understandable | Users must be able to understand both the content and how the interface works. Content should be clear, predictable, and free of unnecessary complexity. |
| Robust | Content must be robust enough to be interpreted reliably by a wide range of user agents — including current and future assistive technologies. |
Conformance levels: A, AA, AAA
WCAG defines specific, testable success criteria across three levels of conformance. Each level builds on the previous one.
| Level | Description |
|---|---|
| A (minimum) | The most basic level. Addresses the most severe barriers and is considered essential for any website. Level A alone will still leave significant barriers for many users. |
| AA (mid-range) | Addresses more barriers and provides much stronger accessibility. The most common target for organisations and the level usually cited in legal standards. Provides good accessibility for most users on most devices. |
| AAA (highest) | The most stringent level. Provides the best experience for the widest range of users, but isn't always achievable for all content types. Strive for it where possible — don't make it a blanket requirement. |