Web Accessibility Resources and Glossary

This page serves as your reference point for accessibility terminology, official standards, tools, and further learning. Bookmark it and return whenever you need to look up a concept or find a resource.

Glossary of Web Accessibility Terms

Accessibility Tree — A simplified representation of the DOM that browsers create for assistive technologies. It contains the semantic information about page elements — their names, roles, states, and properties — that screen readers and other assistive technologies use to present content to users.

Alternative Text (Alt Text) — A text description of non-text content, most commonly images. Alt text is read aloud by screen readers and displayed when images fail to load. It should describe the purpose or content of the image, not merely its visual appearance.

ARIA (WAI-ARIA) — Accessible Rich Internet Applications. A W3C specification that provides additional HTML attributes to improve accessibility of dynamic web content and custom widgets. ARIA adds semantic information for assistive technologies when native HTML semantics are insufficient.

Assistive Technology — Hardware or software that people with disabilities use to interact with digital content. Examples include screen readers (JAWS, NVDA, VoiceOver), screen magnifiers, alternative keyboards, switch devices, voice recognition software, and eye-tracking systems.

Conformance — The degree to which digital content meets the requirements of a specific WCAG level. Full conformance at a given level means all success criteria at that level and below are satisfied for the entire page.

EAA (European Accessibility Act) — EU Directive 2019/882 requiring accessibility of products and services including e-commerce, banking, transport, and telecommunications. Enforceable since June 28, 2025.

EN 301 549 — The harmonized European standard for ICT accessibility. It incorporates WCAG for web content and provides additional requirements for software, documents, hardware, and communication technologies. Conformance with EN 301 549 creates a presumption of conformity with the EAA.

Focus Indicator — A visual indicator (typically an outline or highlight) that shows which element on a page currently has keyboard focus. Essential for keyboard navigation.

Landmark — A region of a page that has been identified as having a specific structural purpose, allowing assistive technology users to navigate directly to it. Common landmarks include banner, navigation, main, complementary, and contentinfo. Created through HTML5 sectioning elements or ARIA landmark roles.

Live Region — An area of a web page that updates dynamically and whose changes should be announced by assistive technologies without the user needing to navigate to that area. Defined using the aria-live attribute with values of "polite" (announced at the next convenient pause) or "assertive" (announced immediately).

POUR — The four principles of WCAG: Perceivable, Operable, Understandable, Robust. All WCAG guidelines and success criteria are organized under these principles.

Screen Reader — Assistive technology software that converts on-screen content into speech or braille output. Screen readers interpret the accessibility tree to present content, navigate page structure, and interact with controls.

Semantic HTML — HTML markup that conveys meaning about the content it contains, as opposed to merely defining its appearance. Using <nav> instead of <div class="nav">, <button> instead of <span onclick>, and <h2> instead of <div class="heading"> are examples of semantic HTML.

Skip Link — A navigation mechanism, typically the first focusable element on a page, that allows keyboard users to bypass repeated blocks of content (such as navigation menus) and jump directly to the main content.

Success Criterion — A specific, testable requirement within WCAG. Each success criterion is assigned a number (e.g., 1.4.3), a descriptive name (Contrast – Minimum), and a conformance level (A, AA, or AAA).

VPAT (Voluntary Product Accessibility Template) — A standardized document format used to describe how a product or service conforms to accessibility standards. VPATs are commonly required in procurement processes, particularly in the US public sector.

WCAG (Web Content Accessibility Guidelines) — The international standard for web accessibility published by the W3C. The current version is WCAG 2.2, containing 86 success criteria organized under four principles and thirteen guidelines.

Official Standards and Specifications

• WCAG 2.2 — The current W3C Recommendation for web content accessibility: w3.org/TR/WCAG22/
• Understanding WCAG 2.2 — Detailed explanations of each success criterion: w3.org/WAI/WCAG22/Understanding/
• Techniques for WCAG 2.2 — Specific implementation techniques: w3.org/WAI/WCAG22/Techniques/
• WAI-ARIA 1.2 — The current ARIA specification: w3.org/TR/wai-aria-1.2/
• ARIA Authoring Practices Guide — Implementation patterns for accessible widgets: w3.org/WAI/ARIA/apg/
• EN 301 549 — European ICT accessibility standard
• European Accessibility Act — Directive 2019/882 full text

Testing Tools

Free automated testing tools: axe DevTools browser extension, WAVE browser extension, Google Lighthouse (built into Chrome), IBM Equal Access Accessibility Checker, Pa11y (command line).

Contrast checkers: WebAIM Contrast Checker, Colour Contrast Analyser (desktop application), Chrome DevTools color picker with contrast ratio.

Screen readers for testing: NVDA (free, Windows), VoiceOver (built into macOS and iOS), TalkBack (built into Android), JAWS (commercial, Windows).

Browser developer tools: Chrome Accessibility panel, Firefox Accessibility Inspector, Edge DevTools accessibility features.

Further Learning

• W3C Web Accessibility Initiative (WAI) — The most authoritative source of accessibility guidance and standards: w3.org/WAI/
• WebAIM — Practical accessibility resources and training: webaim.org
• The A11Y Project — Community-driven accessibility resource: a11yproject.com
• Deque University — Free accessibility courses and certification: dequeuniversity.com