The Web Content Accessibility Guidelines (WCAG) are the internationally recognized technical standards for web accessibility, published by the World Wide Web Consortium (W3C). WCAG defines how to make web content more accessible to people with disabilities, including visual, auditory, physical, speech, cognitive, language, learning, and neurological disabilities.

WCAG is organized around four principles, known as POUR:

• Perceivable — information and UI components must be presentable to users in ways they can perceive (e.g., alt text for images, captions for video).
• Operable — UI components and navigation must be operable by all users (e.g., keyboard accessibility, enough time to interact).
• Understandable — information and UI operation must be understandable (e.g., readable text, predictable navigation).
• Robust — content must be robust enough to be interpreted by a wide variety of user agents and assistive technologies.

WCAG defines three conformance levels:

• Level A — the minimum level of accessibility. Addresses the most fundamental barriers. Failing Level A means some users literally cannot access your content.
• Level AA — the standard target for legal compliance worldwide. This is what the ADA, Section 508, the European Accessibility Act, and most other laws reference.
• Level AAA — the highest level of accessibility. Not typically required by law, but recommended where possible.

Checking WCAG compliance requires a combination of automated testing and manual review. Here is a practical approach:

1. Run an automated scan — tools like ADAfriendly use the axe-core engine to detect violations across your site. Automated testing reliably catches issues like missing alt text, color contrast failures, missing form labels, empty links, and improper heading hierarchy.
2. Test with a keyboard — navigate your entire site using only the Tab, Enter, Escape, and arrow keys. Verify that every interactive element is reachable, that focus is visible, and that you never get trapped.
3. Test with a screen reader — use NVDA (Windows, free), VoiceOver (Mac/iOS, built-in), or TalkBack (Android, built-in) to verify that content is read in a logical order and interactive elements are properly announced.
4. Check zoom and reflow — zoom your browser to 200% and 400%. Content should reflow to fit a single column without horizontal scrolling at 320px viewport width.
5. Review color and contrast — ensure text meets 4.5:1 contrast for normal text and 3:1 for large text. Non-text elements like icons and form borders need 3:1 contrast.