Web Content Accessibility Guidelines

The Web Content Accessibility Guidelines (WCAG) are a set of guidelines for making web content more accessible to people with disabilities, published by the W3C. The guidelines aim to ensure web content is perceivable, operable, understandable, and robust (POUR). Success criteria are organized into three conformance levels: A (low), AA (medium), and AAA (high).

Core principles (POUR)

• Perceivable — present information and UI components in ways users can perceive: provide alternatives for non-text content (images, videos) for people who can't see or hear them, ensure text is readable and understandable, and ensure content is easily distinguishable from its background.
• Operable — ensure UI components and navigation are operable: users must be able to interact with all functionality using various input methods (keyboard, mouse, touch), with enough time to read and use content.
• Understandable — make web content and its operation understandable: clear, easy-to-read text and content; plain language, avoiding jargon or complex terminology; clear instructions and feedback; help avoiding and correcting mistakes.
• Robust — make content interpretable reliably by a wide range of user agents, including assistive technologies: use standard HTML/CSS correctly, ensure cross-browser/device compatibility, and avoid relying on technologies or features that limit accessibility.

Conformance levels

• Level A — the minimum level; failing to meet it makes content unusable for some users entirely.
• Level AA — the level most legal and organizational accessibility requirements target; addresses the most common and significant barriers.
• Level AAA — the highest level; not always achievable for all content types, and WCAG itself notes it's not recommended as a general policy requirement for entire sites.

How WCAG relates to verification and design skills in this collection

WCAG is the formal standard; Accessibility Testing and Screen Reader Testing are how compliance against it is actually verified — automated scanning and manual/user testing for the former, real assistive-technology testing for the latter. Aria Attributes and Screen Reader cover specific technical mechanisms (markup, assistive technology behavior) that WCAG's success criteria are written against.

Common pitfalls

• Treating Level A as sufficient — Level A addresses only the most basic barriers; most real-world accessibility requirements (legal or otherwise) target Level AA.
• Chasing automated-scan compliance without manual verification — automated tools catch a meaningful but limited subset of WCAG success criteria (see Accessibility Testing); many criteria require human judgment or assistive-technology testing to verify.
• Treating WCAG conformance as a one-time certification — content and features change continuously; a page that conformed at launch can drift out of conformance as it's updated without re-verification.
• Confusing WCAG (the standard) with specific legal requirements (ADA, Section 508, EN 301 549, and others) that reference WCAG but have their own scope and enforcement — check which specific legal framework actually applies in a given context.

Learn more

• WCAG official specification (W3C)
• Accessibility Testing, Screen Reader Testing for verifying compliance against this standard.
• Aria Attributes for a specific technical mechanism supporting several WCAG success criteria.