What is WCAG? · Rocket Validator Glossary

WCAG is the shared language used by auditors, legal teams, designers, and engineers when talking about accessibility requirements. It defines testable success criteria and maps them to conformance levels (A, AA, AAA).

Why WCAG matters

Most regulations and procurement frameworks align with WCAG AA. If your team ships features without WCAG alignment, you introduce legal risk and exclude users.

How WCAG works

WCAG is organized around four principles: content must be Perceivable, Operable, Understandable, and Robust (POUR). Under each principle, individual success criteria define what must be true for a page or flow.

In practice, teams typically target AA:

A covers foundational blockers.
AA covers broad usability expectations and is the most common legal target.
AAA is aspirational for many organizations.

Code examples

<!-- Low contrast text: fails WCAG 1.4.3 -->
<p style="color:#8a8a8a;background:#ffffff">Terms and conditions apply.</p>

<!-- Improved contrast -->
<p style="color:#4a4a4a;background:#ffffff">Terms and conditions apply.</p>

Automated validators help by catching recurring WCAG-related defects at scale, while manual audits confirm behavior that tools cannot reliably infer.

An accessibility audit is a structured evaluation of a website or app against accessibility standards, combining automated checks with manual and assistive-technology testing.

ARIA (Accessible Rich Internet Applications) is a set of HTML attributes that add accessibility semantics such as roles, states, and properties to custom UI components.

Color contrast is the luminance difference between foreground and background colors, measured as a ratio, used to determine whether text and UI components are readable for users with low vision.

Keyboard accessibility means every interactive part of a website can be reached and operated using a keyboard alone, with logical focus order and visible focus indication.

A skip navigation link is a hidden or visually accessible anchor link placed at the very beginning of a web page that allows keyboard and screen reader users to bypass repetitive content blocks, such as navigation menus, and jump directly to the main content area.

WCAG Conformance Levels are the three tiers of accessibility compliance—Level A, Level AA, and Level AAA—defined by the Web Content Accessibility Guidelines to classify success criteria by their impact and priority for making web content accessible to people with disabilities.

Text alternatives are textual substitutes for non-text content such as images, icons, videos, and controls, enabling people who cannot perceive the original content to understand its meaning and purpose through assistive technologies like screen readers.

A document language declaration specifies the primary human language of a web page by setting the lang attribute on the <html> element, enabling browsers, screen readers, and other tools to process and present the content correctly.

WCAG Success Criteria are the individual, testable requirements defined by the Web Content Accessibility Guidelines that determine whether web content is accessible to people with disabilities. Each criterion addresses a specific accessibility barrier and is assigned a conformance level of A, AA, or AAA.

The reduced motion preference is an operating system–level setting that users can enable to minimize or eliminate animations, transitions, and other non-essential motion on screen. Web developers can detect this preference using the prefers-reduced-motion CSS media query and adjust or disable animations accordingly.

Content reflow and responsive zoom refers to the ability of web content to adapt its layout when users zoom in up to 400% or resize their viewport, ensuring all information and functionality remains available without requiring horizontal scrolling in two dimensions.

Progressive enhancement is a web design strategy that starts with a baseline of functional, accessible HTML content and layers on CSS styling and JavaScript behavior so that all users receive a working experience regardless of their browser, device, or assistive technology capabilities.

Gestural alternatives and motion activation refer to the WCAG requirements that any functionality triggered by device motion or multipoint/path-based gestures must also be operable through single-pointer actions and conventional controls, so that people with motor impairments can access all features without performing complex physical movements.

Navigation and bypass mechanisms are techniques that allow users to skip past repeated blocks of content and move directly to the main content or specific sections of a web page, primarily benefiting keyboard and screen reader users.

User testing with assistive technologies is the practice of evaluating websites and web applications by having real users operate them with tools like screen readers, switch devices, braille displays, and voice control software to identify accessibility barriers that automated testing alone cannot detect.

Media alternatives and captions are accessibility provisions that make audio and video content perceivable to people who cannot hear the audio track or see the video track, typically through captions, transcripts, and audio descriptions.

XML Accessibility Guidelines (XAG) is a W3C Working Group Note that provides techniques for ensuring XML document formats and applications are designed with accessibility in mind, complementing WCAG by addressing the creation of accessible XML-based languages and content.

Zoom and text resizing refers to the ability of web content to remain readable and functional when users increase the browser's zoom level or adjust the default text size, as required by WCAG Success Criterion 1.4.4 (Resize Text).

A YAML-based accessibility testing configuration is a structured file written in YAML that defines the rules, scope, and behavior of automated accessibility checks run against web content, allowing teams to customize which WCAG success criteria are tested, which pages are included, and how results are reported.

Pointer cancellation and target size are two related WCAG requirements that govern how interactive elements respond to pointer input and how large clickable or tappable areas must be, ensuring that users with motor impairments can interact with web content accurately and without triggering actions by mistake.

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WCAG

Why WCAG matters

How WCAG works

Code examples

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WCAG

Why WCAG matters

How WCAG works

Code examples

Related terms

Help us improve this glossary term

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Pro Trial

Validate at scale.
Ship accessible websites, faster.