Accessibility Glossary
WCAG criteria, patterns, and standards — with interactive demos, detection methods, and audit data.
New to accessibility? Start here. The foundational terms that cause the most real-world barriers — the best first read.
Accessible Name
Every interactive element needs a computed accessible name. Sources (in priority): aria-labelledby → aria-label → <label> → text content → title. Empty name = invisible to assistive tech.
Alternative Text
54% failEvery meaningful image needs a text equivalent describing its purpose — not its appearance. Decorative images get alt="". 54% of homepages have images missing alt text.
Color Contrast
84% failText must meet a 4.5:1 contrast ratio against its background (3:1 for large text ≥18pt/14pt bold). The single most common WCAG failure — found on 84% of homepages in the 2026 WebAIM Million.
Dialog / Modal
65% failFocus trap inside, Escape to close, focus returns to trigger on dismiss. Use <dialog> or role='dialog' + aria-modal='true'. One of the most commonly broken patterns.
Disproportionate Burden
An EAA exemption a service provider can invoke if conformance would impose a disproportionate burden. Not a blanket opt-out: requires a written, documented assessment weighing cost, organisation size, and benefit to users with disabilities. Reviewed and renewed at least every 3 years.
Document Language
16% failEvery page needs lang="xx" on the <html> element. Screen readers use this to switch pronunciation. Missing on 16% of homepages. One-line fix with enormous impact.
Error Identification
62% failErrors must be described in text (not just color), placed near the field, and announce via aria-describedby + role='alert'. Specific and actionable: 'Enter a valid email' not 'Invalid input'.
Focus Management
65% failProgrammatically move focus when context changes: into a modal on open, back to trigger on close, to the next item after deletion, to new content after dynamic loads.
Focus Not Obscured
When an element receives keyboard focus, it must not be entirely hidden by sticky headers, cookie banners, chat widgets, or footers. New in WCAG 2.2 (Level AA). The most common new 2.2 failure in audits.
Focus Visible
68% failEvery interactive element must have a visible focus indicator when navigated to via keyboard. Never use outline:none without a replacement. WCAG 2.2 adds 2.4.11 (Focus Appearance) requiring minimum area and contrast.
Form Input Labels
49% failEvery input needs a visible, programmatically associated <label for='id'>. Placeholder is not a label. Found missing on 49% of homepages. The second most common WCAG failure after contrast.
Harmonised Standards
Technical standards adopted by a European Standards Organisation and referenced in the Official Journal of the EU. Conformance with a harmonised standard creates a 'presumption of conformity' with the corresponding EAA requirements. For ICT services, the operative standard is EN 301 549.
In-Scope Services (EAA)
The EAA covers a defined list of consumer services: e-commerce (B2C); banking services for consumers; e-books and dedicated software; electronic communications services; access to audiovisual media services; passenger transport (web, apps, e-ticketing, terminals); and emergency communications to 112. Other digital services are outside the directive's scope.
Info & Relationships
60% failStructure conveyed visually (headings, lists, tables, form groups) must also be conveyed programmatically. If it looks like a heading, it must be a heading element.
Keyboard Accessible
78% failAll functionality must be operable with keyboard alone — Tab, Shift+Tab, Enter, Space, Escape, Arrow keys. No keyboard traps. Affects motor-disability users, switch users, power users, and screen reader users.
Name, Role, Value
Every interactive element must expose its name (label), role (button, link, checkbox…), and state (expanded, checked, disabled…) to assistive technology. The foundation of everything.
WCAG Level AA
The legal standard worldwide — 24 additional criteria (55 total with A). Includes color contrast (1.4.3), reflow (1.4.10), focus visible (2.4.7), and all 4 new WCAG 2.2 AA criteria. Target this level. Referenced by ADA, EAA, Section 508, and EN 301 549.