Web accessibility ensures digital content and applications are usable by everyone—including people with visual, auditory, motor, or cognitive disabilities—through standards like WCAG (Web Content Accessibility Guidelines) and ARIA (Accessible Rich Internet Applications). It's not just a legal requirement under laws like the ADA and Section 508, but a fundamental principle of inclusive design: when you build for accessibility, you create better experiences for all users—whether someone is navigating by keyboard, using a screen reader, experiencing low vision, or simply using a mobile device in bright sunlight. The European Accessibility Act (EAA) began enforcement in June 2025, extending accessibility obligations to private-sector digital products across the EU. WCAG 3.0 (still a working draft, not expected before 2028) is introducing a Bronze/Silver/Gold conformance model and the Advanced Perceptual Contrast Algorithm (APCA) to replace the current contrast formula. In the meantime, WCAG 2.2 Level AA is the operative legal benchmark globally—proper semantic HTML and ARIA attributes are not afterthoughts but core architectural decisions that determine whether your site works for 15% of the world's population.
What This Cheat Sheet Covers
This topic spans 22 focused tables and 191 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: WCAG Principles and Conformance Levels
The four POUR principles form the foundation of every WCAG version. Understanding them before diving into individual success criteria gives you a mental model for diagnosing accessibility issues quickly—if something fails, it always maps back to one of these four principles.
| Principle | Example | Description |
|---|---|---|
Alt text for images, captions for video | • Information must be presentable in ways users can perceive—not just visual • includes text alternatives, captions, and color contrast | |
Full keyboard navigation support | • Interface components must be operable through keyboard, mouse, touch, or assistive tech • includes keyboard access, sufficient time, and seizure safety | |
Clear error messages, consistent navigation | Content and operation must be understandable—predictable behavior, readable text, clear instructions, and helpful error identification. | |
Valid HTML, compatible with assistive tech | Content must be robust enough to be reliably interpreted by current and future user agents, including assistive technologies. |