accessibility-patterns

Accessibility Patterns

WCAG 2.2 AA Requirements

Perceivable

Kriter	Kural	Kontrol
1.1.1	Non-text content alt text	<img alt="description">
1.3.1	Semantic HTML	Headings, landmarks, lists
1.4.3	Color contrast	4.5:1 normal text, 3:1 large
1.4.11	UI component contrast	3:1 borders, icons

Operable

Kriter	Kural	Kontrol
2.1.1	Keyboard accessible	Tab, Enter, Space, Escape
2.4.3	Focus order	Logical tab sequence
2.4.7	Focus visible	Visible focus indicator
2.5.8	Target size	Min 24x24px (44x44px önerilir)

Understandable

Kriter	Kural	Kontrol
3.1.1	Language of page	<html lang="tr">
3.2.1	On focus	No unexpected context change
3.3.1	Error identification	Clear error messages
3.3.2	Labels or instructions	Form labels visible

ARIA Patterns

<!-- Dialog -->
<div role="dialog" aria-modal="true" aria-labelledby="title">
  <h2 id="title">Confirm</h2>
  <button aria-label="Close dialog">×</button>
</div>

<!-- Tabs -->
<div role="tablist">
  <button role="tab" aria-selected="true" aria-controls="panel1">Tab 1</button>
  <button role="tab" aria-selected="false" aria-controls="panel2">Tab 2</button>
</div>
<div role="tabpanel" id="panel1">Content 1</div>

<!-- Live region (dynamic updates) -->
<div aria-live="polite" aria-atomic="true">
  3 new messages
</div>

Keyboard Navigation

// Focus trap (modal/dialog)
function useFocusTrap(ref: RefObject<HTMLElement>) {
  useEffect(() => {
    const focusable = ref.current?.querySelectorAll(
      'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
    )
    const first = focusable?.[0] as HTMLElement
    const last = focusable?.[focusable.length - 1] as HTMLElement

    function handleKeyDown(e: KeyboardEvent) {
      if (e.key !== 'Tab') return
      if (e.shiftKey && document.activeElement === first) {
        e.preventDefault(); last.focus()
      } else if (!e.shiftKey && document.activeElement === last) {
        e.preventDefault(); first.focus()
      }
    }
    ref.current?.addEventListener('keydown', handleKeyDown)
    first?.focus()
    return () => ref.current?.removeEventListener('keydown', handleKeyDown)
  }, [ref])
}

Skip Links

<a href="#main-content" class="skip-link">Skip to main content</a>
<!-- ... navigation ... -->
<main id="main-content">...</main>

<style>
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  z-index: 100;
}
.skip-link:focus { top: 0; }
</style>

Motion Preferences

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

Testing

# axe-core (automated)
npx @axe-core/cli https://localhost:3000

# Lighthouse accessibility audit
lighthouse --only-categories=accessibility https://localhost:3000

Checklist

• Semantic HTML (headings, landmarks, lists)
• Alt text on all images
• Color contrast 4.5:1 (text), 3:1 (UI)
• Keyboard navigable (tab order logical)
• Focus visible indicator
• Skip link to main content
• Form labels and error messages
• ARIA roles where needed
• prefers-reduced-motion respected
• axe-core test pass

Anti-Patterns

• <div onclick> instead of <button>
• Color-only information (add icon/text)
• Auto-playing video/audio
• Removing focus outline without replacement
• Using ARIA when native HTML suffices