Accessibility Glossary

JavaScript widgets that claim to fix accessibility automatically. They don't — pages with overlays have more errors, not fewer. 25% of ADA lawsuits in 2024 involved overlay widgets. The FTC fined one provider $1M in 2025 for misleading claims.

Public declaration of accessibility commitment, conformance level, known limitations, and contact information for reporting barriers. Required under EAA and many national laws. WAI provides a generator tool.

The parallel DOM that assistive technology reads. If an element isn't in the accessibility tree, it doesn't exist for screen reader users. Inspect via DevTools → Accessibility tab.

Authentication must not require cognitive function tests (memorizing, transcribing, puzzles) unless an alternative exists. Allow paste in password fields. Support password managers. New in WCAG 2.2.

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.

Use <details>/<summary> or button + aria-expanded + aria-controls. Arrow keys optional. Content panel must be associated with its trigger.

US: ADA applies to private sector (case law, 4000+ lawsuits in 2024). Section 508 applies to federal agencies and contractors. Both align to WCAG 2.1 AA. DOJ Title II rule requires compliance by April 2026.

Users perceive aesthetically pleasing designs as more usable — even when they're not. Beautiful design builds tolerance for minor friction. But aesthetics can't compensate for fundamental accessibility failures.

Visual cues that indicate how an element can be used. Buttons should look clickable (raised, colored, labeled). Links should look tappable (underlined, colored). Flat design often destroys affordance — add it back with shadows, borders, or underlines.

Every meaningful image needs a text equivalent describing its purpose — not its appearance. Decorative images get alt="". 54% of homepages have images missing alt text.

80% of homepages use ARIA — and those pages have 2× more errors than pages without. ARIA doesn't add behavior, only semantics. Misused ARIA is worse than no ARIA. Five rules: don't use ARIA if native works.

Any device or software that helps people with disabilities use technology. Includes screen readers, magnifiers, switch devices, eye trackers, voice control (Dragon), braille displays, and alternative keyboards. Design and test for the full range.

Videos must describe important visual content in the audio track for blind users. Required when dialogue alone doesn't convey what's happening on screen.

Tools like axe, WAVE, Lighthouse catch ~30-40% of WCAG issues automatically. Good for contrast, alt text, labels, ARIA attributes. Can't catch focus order, reading comprehension, or keyboard traps.

Use nav with aria-label='Breadcrumb', an ordered list, and aria-current='page' on the last item. Separators should be decorative (CSS or aria-hidden). Helps orientation for all users.

Pre-recorded video needs synchronized captions. Pre-recorded audio needs a transcript. Live video needs real-time captions (Level AA). Benefits 430M people with hearing loss plus anyone in a noisy environment.

Provide pause/stop controls. Support keyboard navigation (arrows for slides). Role='group' on each slide with aria-roledescription='slide'. Auto-rotation must respect prefers-reduced-motion.

Too many options leads to decision paralysis and reduced satisfaction (paradox of choice). Limit visible options, use defaults, and allow filtering. Directly overlaps with cognitive load reduction.

Mental effort to process information. More options = slower decisions (Hick's Law). More fields = more abandonment. Chunk content, simplify choices, eliminate unnecessary inputs.

Tools that simulate color vision deficiencies: protanopia (no red), deuteranopia (no green), tritanopia (no blue), achromatopsia (no color). Chrome DevTools has a built-in simulator. Use to verify color is never the only indicator.

Text 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.

A text input with a popup list of options. One of the hardest ARIA patterns: role='combobox' + aria-expanded + aria-activedescendant + listbox. Broken implementations are everywhere — test with screen readers.

Conformance is per-page, not per-site. Level AA means all A + AA criteria pass on that page. Claims should specify version (2.2), level (AA), scope (pages/processes), and date. Partial conformance exists for third-party content you don't control.

The procedure used to demonstrate that a product meets the EAA accessibility requirements. For products covered by the EAA, this is internal production control (Module A — Annex IV of the directive): the manufacturer compiles a technical file, performs the assessment themselves, draws up the EU Declaration of Conformity, and affixes the CE marking.

If help mechanisms (contact info, chat, FAQ link) appear on multiple pages, they must be in the same relative order. New in WCAG 2.2 (Level A). Does not require providing help — only consistency when you do.

Components with the same function must be identified consistently. If 'Search' is a label on one page, don't call it 'Find' on another.

Navigation mechanisms repeated across pages must appear in the same relative order. Don't rearrange menus between pages.

Deceptive UI tricks that manipulate users: hidden costs, forced continuity, misdirection, confirm-shaming, roach motels, disguised ads. The ethical counterpoint to Laws of UX. Increasingly illegal under GDPR, FTC enforcement, and the EU Digital Services Act.

Use <th> with scope='col'/'row'. Add <caption> or aria-labelledby. Never use tables for layout. Only 19% of observed tables had valid markup in the 2026 WebAIM Million.

Charts and graphs need a text alternative — a short summary, a data table, or both. Don't tell data series apart by color alone; add labels, patterns, or direct annotations. Bars, lines, and segments must meet 3:1 non-text contrast.

Notoriously inaccessible. Must support keyboard navigation (arrow keys for days, page up/down for months). Always provide a text input alternative. Native <input type='date'> is often the best option.

Each page needs a unique, descriptive <title>. Screen reader users hear this first. Pattern: 'Page Name — Section — Site Name'. Helps all users with tabs and history.

The body each EU Member State names to receive complaints, monitor compliance, and where applicable impose sanctions under the EAA. Some Member States designate a single accessibility authority; others split responsibility between sectoral regulators (e.g., banking, transport, telecoms).

Focus 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.

Disability isn't one fixed group. It can be permanent (one arm), temporary (a broken arm), or situational (holding a baby). Solve for one and you extend to many — the curb-cut effect: curb ramps built for wheelchairs also help strollers, luggage, and carts.

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.

Every 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.

Headings, lists, tables, and reading order must be structurally encoded — not just visually styled. Applies to Word, PowerPoint, InDesign, and Google Docs. Export to tagged PDF.

Productivity soars when response time is under 400ms. Interactions that feel instant maintain flow state. Use skeleton screens, optimistic UI, and progress indicators when latency exceeds this threshold.

Any drag operation must have a non-dragging alternative (buttons, form controls). New in WCAG 2.2. Affects users who can't perform precise pointer movements.

Sanctions for EAA non-compliance are set by each Member State and must be 'effective, proportionate and dissuasive.' Penalty ceilings vary widely: Germany up to €100,000 per infringement under BFSG; Ireland up to €60,000 plus possible imprisonment; the Netherlands and France use periodic-penalty and administrative-fine regimes. Repeat or serious cases can trigger market-access restriction.

HTML email renders across a fragmented stack — Outlook on Windows uses the Word engine, Gmail strips style blocks, Apple Mail enforces dark-mode color inversion. Build with semantic tables for layout, real text over image-only designs, descriptive alt text, 4.5:1 contrast (in both light and dark), descriptive link text, and a declared language. Most marketing emails fail at least one of these.

European standard for ICT accessibility requirements. Incorporates WCAG and extends to software, hardware, documentation, and support services. Referenced by the EAA and EU Web Accessibility Directive.

Errors 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'.

For legal, financial, or data-deletion actions: let users review before submitting, allow undo, or confirm the action. Reduces consequences of mistakes for everyone.

Make errors easy to fix, not punishing. Preserve form data on validation failure. Allow undo. Clearly identify what went wrong and how to fix it. Norman's 'Design of Everyday Things' principle.

EU directive requiring accessible products and digital services since June 28, 2025. Applies to e-commerce, banking, transport, e-books, and more. Non-compliance carries market access risk.

Time to reach a target = f(distance, size). Larger, closer targets are faster to hit. Make primary actions big and near the cursor. Applies directly to target size accessibility (WCAG 2.5.8).

Total immersion in a task where challenge matches skill. Design for flow: minimize interruptions, provide clear goals, give immediate feedback, and remove unnecessary friction. Accessibility barriers break flow.

Focus indicators must be at least 2px thick around the perimeter with 3:1 contrast between focused and unfocused states. Level AAA in WCAG 2.2. The criterion that finally defines what 'visible' means quantitatively.

Programmatically 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.

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.

Tab order must follow a logical reading sequence — typically left-to-right, top-to-bottom. Avoid positive tabindex values. CSS layout changes (order, flex-direction) can break focus order.

Every 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.

Operating systems let people swap every color for their own palette (Windows High Contrast / `forced-colors` mode). Don't fight it: use semantic HTML, keep meaning out of background images, and check that content still reads after the swap.

Every 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.

An EAA exemption where meeting an accessibility requirement would require a fundamental alteration of the product or service — changing its basic nature. Narrower than disproportionate burden. Same documentation duty applies.

Motivation increases as you approach a goal. Progress bars, step counters, and 'almost there' messaging accelerate completion. Loyalty cards that start pre-stamped outperform empty ones.

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.

One <h1> per page. Headings in logical order without skipping levels (h1→h2→h3, never h1→h3). Screen reader users navigate by heading — 67.5% use headings to find information.

Decision time increases with the number and complexity of choices. Reduce options, use progressive disclosure, break complex tasks into steps. Directly supports cognitive accessibility.

Don't use images of text — use real text styled with CSS. Images of text can't be resized, reflowed, recolored, or read by screen readers. Exception for logos.

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.

Design for the full range of human diversity from the start — not as a remediation step. Microsoft's framework: recognize exclusion, learn from diversity, solve for one/extend to many.

Structure conveyed visually (headings, lists, tables, form groups) must also be conveyed programmatically. If it looks like a heading, it must be a heading element.

Inputs collecting personal data (name, email, address, credit card) must have autocomplete attributes. Helps autofill and assistive tech identify fields: autocomplete='email', 'given-name', etc.

Users spend most time on other sites — they expect yours to work the same way. Leverage familiar patterns (nav on top, logo links home, search in header). Novelty has a cost.

All 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.

The accessible name of a component must include its visible text. If a button says 'Search', its aria-label can't be 'Find items'. Voice control users say what they see.

Semantic containers: <header>, <nav>, <main>, <aside>, <footer>. Screen reader users jump between landmarks. Every page needs exactly one <main>.

Elements sharing a bounded area are perceived as grouped (Gestalt). Cards, sections, fieldsets — boundaries create relationships without needing proximity alone. Supports info & relationships (WCAG 1.3.1).

Objects near each other are perceived as a group (Gestalt). Use spacing to create visual relationships — related form fields close together, unrelated sections further apart. Replaces the need for borders.

People interpret complex images as the simplest form possible. Reduce visual noise, favor clean geometry, and avoid ambiguous layouts. The brain seeks order — give it order.

Similar elements (shape, color, size) are perceived as related (Gestalt). Consistent styling for all buttons, all links, all headings. Breaking similarity draws attention — use intentionally for emphasis.

Visually connected elements (lines, arrows, shared color) are perceived as more related than disconnected elements. Breadcrumbs, step indicators, and flow diagrams leverage this principle.

Link text must describe its destination — even out of context. Avoid 'click here', 'read more', 'learn more'. Empty links (no text at all) found on 47% of homepages.

A part of the page marked with `aria-live` so screen readers announce changes without moving focus. Use `polite` for routine updates (a results count) and `assertive` for urgent ones (an error). The region must exist before its text changes.

Keyboard-only navigation, screen reader testing (NVDA/JAWS/VoiceOver), zoom to 400%, check focus order, verify ARIA states. Catches the 60% that automated tools miss.

The national authority each EU Member State designates to enforce the EAA against products. Powers include requesting documentation, inspecting services, ordering corrective action, restricting market access, and imposing penalties. For services, Member States designate a separate authority responsible for service compliance.

Each EU Member State must transpose the EAA into national law. Operators comply with the national transposition, not the directive directly. Penalties, exemption procedures, and (in some cases) the scope of covered services vary between Member States.

Users carry compressed expectations of how systems work. Mismatches between mental models and actual behavior cause errors and frustration. Research reveals models; design should align with them, not fight them.

Microenterprises (fewer than 10 employees AND annual turnover or balance sheet ≤ €2M) that provide services are exempt from the EAA's accessibility requirements. The exemption does NOT extend to microenterprises that place products on the market — those must still comply.

Working memory holds ~7 (±2) items. Chunk information into groups of 3–5. Phone numbers, card numbers, and step indicators all use chunking. Especially critical for users with cognitive disabilities.

Hamburger menus need: button trigger (not div) with aria-expanded, focus trap when open, Escape to close, focus returns to trigger. Content behind the menu should be inert when open.

Respect prefers-reduced-motion. No auto-playing content that flashes more than 3 times per second. Parallax, scroll-triggered animations, and auto-play video must be pauseable.

Every interactive element must expose its name (label), role (button, link, checkbox…), and state (expanded, checked, disabled…) to assistive technology. The foundation of everything.

UI components and graphical objects need at least 3:1 contrast. Applies to icons, form borders, chart segments, focus indicators — anything meaningful that isn't text.

The simplest solution is usually the best. Among designs that solve the problem equally well, prefer the one with fewer elements, fewer steps, and less cognitive overhead. Simplicity is a feature.

Wrap in nav with aria-label='Pagination'. Mark current page with aria-current='page'. Use meaningful link text ('Page 3') not just numbers. Previous/Next need clear labels, not just arrows.

Users never read manuals — they start using software immediately. Design for exploration, not instruction. Progressive disclosure, inline help, and sensible defaults serve active users.

80% of effects come from 20% of causes. Focus on the 20% of features, flows, and pages that serve 80% of users. In accessibility: fixing the 6 most common WCAG failures addresses 96% of detected errors.

Tasks expand to fill available time. Reduce form fields and you reduce completion time. Set clear expectations with time estimates. Constrained interfaces (character limits, deadlines) drive efficiency.

Tagged PDFs with reading order, alt text, proper structure, and bookmarks. Only 19% of observed tables in PDFs were properly coded. Scan → OCR does not equal accessible.

Experiences are judged by their peak intensity and their ending — not the average. Invest in delightful success states and smooth offboarding. A painful checkout overshadows good browsing.

Write so the widest audience understands on the first read: short sentences, everyday words, one idea per paragraph, and abbreviations spelled out the first time. Helps people with cognitive differences, non-native speakers, and anyone in a hurry.

Anything that uses a complex gesture — pinch-to-zoom, swipe along a path, two-finger rotate — must also work with a single tap or click. Maps, sliders, and carousels are common offenders. Affects people who can't make precise movements.

Be liberal in what you accept, conservative in what you send. Accept varied input formats (dates, phone numbers, spaces in card numbers). Output clean, consistent, predictable interfaces.

The four pillars organizing all WCAG criteria: Perceivable (can users sense it?), Operable (can they interact?), Understandable (can they comprehend?), Robust (does it work with assistive tech?). If any pillar fails, the content is inaccessible.

If a product or service conforms to a harmonised standard whose reference is published in the Official Journal of the EU, it is *presumed* to conform to the EAA requirements that standard covers. Conforming to EN 301 549 (where referenced) creates this presumption for ICT.

Show essential info first, details on demand. Reduces overwhelm, supports scanning, and aligns with how people actually read (F-pattern). Especially valuable for users with cognitive disabilities.

Write at a lower secondary education reading level when possible (WCAG AAA). Short sentences, common words, one idea per paragraph. Flesch-Kincaid Grade 8 or below is a good target.

Don't ask users to re-enter information they've already provided in the same process. Auto-populate or let them select previous values. New in WCAG 2.2. Helps users with cognitive and memory disabilities.

Content must reflow to a single column at 320px wide (400% zoom) without horizontal scrolling. Exceptions for data tables, toolbars, and maps.

Software that reads content aloud and enables keyboard navigation. NVDA (Windows, free), JAWS (Windows, commercial), VoiceOver (macOS/iOS, built-in), TalkBack (Android). Each has different behaviors and quirks.

Nothing on the page may flash more than three times in any one second — fast flashing can trigger seizures in people with photosensitive epilepsy. Avoid strobing animation, flashing ads, and rapid red flashes. When in doubt, don't flash.

People focus on stimuli relevant to their current goal and filter out the rest. Important information must be visually prominent — not hidden in dense layouts. Banner blindness is selective attention at work.

Use elements for their meaning: <button> not <div onclick>, <nav> not <div class='nav'>, <main>, <article>, <aside>. The first rule of ARIA: don't use ARIA if a native element works.

Instructions can't depend on shape, size, position, or sound alone. "Press the round green button on the right" fails for anyone who can't see it — always add a text label: "Press Submit".

People best remember the first (primacy) and last (recency) items in a series. Place key actions and navigation at the start and end of lists. Mobile bottom tabs leverage recency.

A mechanism to bypass repeated navigation and jump to main content. Typically the first focusable element on the page. Only ~13% of homepages have one.

Dynamic status updates (search results count, form success, loading) must be announced without moving focus. Use role='status' or aria-live='polite'.

role='tablist' → role='tab' → role='tabpanel'. Arrow keys move between tabs, Tab moves into the panel. aria-selected on active tab. One of the trickiest ARIA patterns to get right.

Interactive targets need a minimum 24×24px area (Level AA, new in WCAG 2.2). 44×44px at Level AAA. Affects users with tremors, limited dexterity, and all mobile users.

Every system has irreducible complexity. The question is who bears it — the user or the system. Good design absorbs complexity so users don't have to. Autocomplete, smart defaults, and wizards are examples.

No loss of content when users override line height to 1.5×, paragraph spacing to 2×, letter spacing to 0.12em, and word spacing to 0.16em. Tests low-vision user overrides.

If content has a time limit, users must be able to turn off, adjust, or extend it (at least 10× the default). Session timeouts must warn before expiry. Auto-rotating carousels need pause controls.

Transient messages must use role='status' or aria-live='polite' so screen readers announce them. Must not auto-dismiss too quickly (<5s minimum). Must be dismissible. Must not steal focus from the user's task.

Must be triggerable by focus (not just hover). Dismissible with Escape. Persistent while hovering over it. Use aria-describedby to associate with trigger. Avoid for critical information.

Color must not be the only visual means of conveying information. Add icons, patterns, underlines, or text labels alongside color coding. Affects 300M people with color vision deficiency.

All controls keyboard-accessible. Captions toggle visible and labeled. Volume, play/pause, seek, fullscreen all need accessible names. Captions must be synchronized. Provide transcript link nearby.

Software like Dragon, plus the dictation built into every phone, lets people operate a device entirely by speaking. Users say a button's visible label to activate it — which is why a control's visible text must match its accessible name.

The item that differs from the rest is most remembered (isolation effect). Highlight CTAs, error states, and new features by making them visually distinct. But don't rely on color alone (WCAG 1.4.1).

Voluntary Product Accessibility Template: standardized format for documenting a product's accessibility conformance. Produces an Accessibility Conformance Report (ACR). Required for US government procurement.

Web Content Accessibility Guidelines: 4 principles, 13 guidelines, 86 success criteria at Levels A/AA/AAA. Level AA is the legal standard worldwide. 2.2 adds 9 new criteria for mobile, cognitive, and focus.

Next-generation accessibility guidelines in early draft. Major restructuring: outcome-based testing, severity scoring, broader scope (apps, documents, XR). Years from W3C Recommendation. Don't wait for it — implement WCAG 2.2 now.

The minimum baseline — 31 success criteria addressing the most critical barriers. Includes alt text (1.1.1), keyboard access (2.1.1), page titles (2.4.2), and error identification (3.3.1). Level A alone is not sufficient for legal compliance. (WCAG 2.2 marks 4.1.1 Parsing as obsolete, so it is no longer counted.)

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.

Enhanced accessibility — 31 additional criteria (86 total: 31 A + 24 AA + 31 AAA). Includes sign language for video (1.2.6), 7:1 contrast (1.4.6), 44×44px targets (2.5.5), and reading level (3.1.5). Aspirational, not achievable for all content. Cherry-pick criteria that benefit your audience.

EU Directive 2016/2102 — the WAD. Requires public-sector body websites and mobile apps to meet EN 301 549 (which embeds WCAG 2.1 AA). Distinct from the EAA, which targets private-sector products and services. Some operators fall under both regimes.

The cognitive system that temporarily holds information needed to complete tasks. Limited to ~4 chunks. Reduce reliance on memory: show don't recall, persist state, and keep related info visible together.

People remember incomplete tasks better than completed ones. Progress indicators, partially filled profiles, and onboarding checklists leverage this to drive completion. Use ethically — not as a dark pattern.

Test at 200% zoom (WCAG 1.4.4) and 400% zoom / 320px viewport (WCAG 1.4.10 Reflow). Check for: horizontal scrolling, overlapping text, clipped content, broken layouts, and unreadable text. Browser zoom ≠ OS magnification — test both.