Axe Core

Accessibility implementation guide aligned with WCAG 2.2 Level AA, WAI-ARIA 1.2, and WCAG2ICT.

Standards Reference

WCAG 2.2 New Success Criteria

Critical Success Criteria

Perceivable

Operable

Understandable

Robust

Semantic HTML (Mandatory)

// REQUIRED: Landmark structure
<header role="banner">...</​header>
<nav aria-label="Main">...</​nav>
<main role="main">...</​main>
<aside role="complementary">...</​aside>
<footer role="contentinfo">...</​footer>

// PROHIBITED: Div-based structure
<div class="header">  // SC 1.3.1 violation
<div onClick={...}>   // SC 2.1.1, 4.1.2 violation

Top 10 Violations with Fixes

1. Missing button name (SC 4.1.2)

// BAD
<button onClick={handleDelete}><Trash2 /></​button>

// GOOD
<button type="button" aria-label="Delete" onClick={handleDelete}>
  <Trash2 aria-hidden="true" />
</​button>

2. Div as interactive element (SC 2.1.1, 4.1.2)

// BAD
<div className="btn" onClick={handleClick}>Save</​div>

// GOOD
<button type="button" onClick={handleClick}>Save</​button>

3. Missing form label (SC 1.3.1, 4.1.2)

// BAD
<input placeholder="Search..." />

// GOOD
<label htmlFor="search">Search</​label>
<input id="search" type="search" />
// OR
<input type="search" aria-label="Search files" />

4. Color-only information (SC 1.4.1)

// BAD
<input className={error ? "border-red-500" : ""} />

// GOOD
<input aria-invalid={!!error} aria-describedby="error-msg" />
{error && <span id="error-msg" role="alert">{error}</​span>}

5. Missing alt text (SC 1.1.1)

// BAD
<img src="/​logo.png" />

// GOOD: Informative
<img src="/​logo.png" alt="Company logo" />

// GOOD: Decorative
<img src="/​decoration.png" alt="" role="presentation" />

6. Insufficient contrast (SC 1.4.3)

/​* BAD: ~2.5:1 ratio */
.muted { color: oklch(75% 0 0); }

/​* GOOD: 4.5:1+ ratio */
.muted { color: oklch(45% 0 0); }

Color Vision Deficiency (CVD) Support

Never rely on color alone to convey information (SC 1.4.1):

// BAD: Color-only status
<span className={status === "error" ? "text-red-500" : "text-green-500"}>
  {status}
</​span>

// GOOD: Color + icon + text
<span className={status === "error" ? "text-red-500" : "text-green-500"}>
  {status === "error" ? <AlertCircle aria-hidden /> : <CheckCircle aria-hidden />}
  {status === "error" ? "Error" : "Success"}
</​span>

Testing tools:

• Chrome DevTools: Rendering → Emulate vision deficiencies
• Sim Daltonism (macOS)
• Color Oracle (Windows)

7. Missing focus indicator (SC 2.4.7)

// BAD
<button className="outline-none">Action</​button>

// GOOD
<button className="focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2">
  Action
</​button>

8. Skipped heading levels (SC 1.3.1)

// BAD
<h1>Title</​h1>
<h3>Subsection</​h3>  // h2 skipped

// GOOD
<h1>Title</​h1>
<h2>Subsection</​h2>

9. Small touch target (SC 2.5.8)

// BAD: 16x16
<button className="p-0.5"><X size={12} /></​button>

// GOOD: 24x24 minimum
<button className="p-2 min-w-6 min-h-6"><X size={16} /></​button>

10. Auto-playing media (SC 1.4.2)

// BAD
<video src="/​demo.mp4" autoPlay />

// GOOD
<video src="/​demo.mp4" autoPlay muted />

Component Patterns

TreeView (APG)

<ul role="tree" aria-label="File explorer">
  <li
    role="treeitem"
    aria-expanded={isExpanded}
    aria-selected={isSelected}
    aria-level={level}
    aria-setsize={siblingCount}
    aria-posinset={position}
    tabIndex={isFocused ? 0 : -1}  // Roving tabindex
  >
    <span>{name}</​span>
    {hasChildren && (
      <ul role="group">{children}</​ul>
    )}
  </​li>
</​ul>

Keyboard: ↓↑ navigate, → expand/​child, ← collapse/​parent, Enter activate, Space toggle, Home/​End boundaries

Modal Dialog (APG)

<div
  role="dialog"
  aria-modal="true"
  aria-labelledby="dialog-title"
  tabIndex={-1}
>
  <h2 id="dialog-title">Title</​h2>
  {/​* Focus trap: Tab cycles within */​}
  {/​* Escape: closes dialog */​}
  {/​* On close: restore focus to trigger */​}
</​div>

Toast/​Alert

<div role="alert" aria-live="polite" aria-atomic="true">
  {message}
</​div>
// Error: aria-live="assertive"

Focus Management

Roving Tabindex

// Only focused item has tabIndex={0}
{items.map((item, i) => (
  <button
    key={item.id}
    tabIndex={focusedIndex === i ? 0 : -1}
    onKeyDown={(e) => handleArrowKeys(e, i)}
  />
))}

Focus Restoration

// Store trigger before modal opens
const triggerRef = useRef<HTMLElement>(null)
const openModal = (e) => { triggerRef.current = e.currentTarget; setOpen(true) }
const closeModal = () => { setOpen(false); triggerRef.current?.focus() }

Motion Preferences

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

Validation Workflow

Automated (CI)

# axe-core
npx @axe-core/​cli <url> --tags wcag2a,wcag2aa,wcag22aa --exit

# Lighthouse
npx lighthouse <url> --only-categories=accessibility --output=json

# pa11y
npx pa11y <url> --standard WCAG2AA

Manual Checklist

1. Keyboard: Tab through all controls, verify reachability
2. Focus: Confirm visible 2px+ ring on every interactive element
3. Screen reader: Test with NVDA/​VoiceOver, verify announcements
4. Zoom: Scale to 200%, verify no content loss
5. Motion: Enable prefers-reduced-motion, verify compliance
6. Contrast: Check text 4.5:1, UI components 3:1
7. Color blindness: Test with vision deficiency emulation

Screen Reader Testing Guide

NVDA (Windows):

1. Press Insert+Space to toggle focus mode
2. Insert+Down to read all
3. H to navigate headings, D for landmarks
4. Verify: role, name, state announced correctly

VoiceOver (macOS):

1. Cmd+F5 to enable
2. VO+A to read all
3. VO+U to open rotor (headings, links, landmarks)
4. Verify: proper navigation, state changes announced

Mobile (TalkBack/​VoiceOver):

1. Swipe right to move forward
2. Double-tap to activate
3. Verify: touch targets accessible, gestures work

Testable Assertions Template

## Component: [Name]

### WCAG Compliance
- [ ] SC 1.3.1: Semantic structure
- [ ] SC 2.1.1: Keyboard operable
- [ ] SC 2.4.7: Focus visible
- [ ] SC 4.1.2: Accessible name

### Screen Reader
Expected: "[Role]: [Name], [State]"