Accessibility

Accessibility (a11y)

Comprehensive accessibility guidelines based on WCAG 2.2 and Lighthouse accessibility audits. Goal: make content usable by everyone, including people with disabilities.

WCAG Principles: POUR

Conformance levels

---

Perceivable

Text alternatives (1.1)

Images require alt text:

<!-- ❌ Missing alt -->
<img src="chart.png">

<!-- ✅ Descriptive alt -->
<img src="chart.png" alt="Bar chart showing 40% increase in Q3 sales">

<!-- ✅ Decorative image (empty alt) -->
<img src="decorative-border.png" alt="" role="presentation">

<!-- ✅ Complex image with longer description -->
<figure>
  <img src="infographic.png" alt="2024 market trends infographic" 
       aria-describedby="infographic-desc">
  <figcaption id="infographic-desc">
    <!-- Detailed description -->
  </figcaption>
</figure>

Icon buttons need accessible names:

<!-- ❌ No accessible name -->
<button><svg><!-- menu icon --></svg></button>

<!-- ✅ Using aria-label -->
<button aria-label="Open menu">
  <svg aria-hidden="true"><!-- menu icon --></svg>
</button>

<!-- ✅ Using visually hidden text -->
<button>
  <svg aria-hidden="true"><!-- menu icon --></svg>
  <span class="visually-hidden">Open menu</span>
</button>

Visually hidden class:

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

Color contrast (1.4.3, 1.4.6)

/* ❌ Low contrast (2.5:1) */
.low-contrast {
  color: #999;
  background: #fff;
}

/* ✅ Sufficient contrast (7:1) */
.high-contrast {
  color: #333;
  background: #fff;
}

/* ✅ Focus states need contrast too (3:1 against background, WCAG 1.4.11) */
:focus-visible {
  outline: 2px solid currentColor;
  outline-offset: 2px;
}

Don't rely on color alone:

<!-- ❌ Only color indicates error -->
<input class="error-border">
<style>.error-border { border-color: red; }</style>

<!-- ✅ Color + icon + text -->
<div class="field-error">
  <input aria-invalid="true" aria-describedby="email-error">
  <span id="email-error" class="error-message">
    <svg aria-hidden="true"><!-- error icon --></svg>
    Please enter a valid email address
  </span>
</div>

Media alternatives (1.2)

<!-- Video with captions -->
<video controls>
  <source src="video.mp4" type="video/mp4">
  <track kind="captions" src="captions.vtt" srclang="en" label="English" default>
  <track kind="descriptions" src="descriptions.vtt" srclang="en" label="Descriptions">
</video>

<!-- Audio with transcript -->
<audio controls>
  <source src="podcast.mp3" type="audio/mp3">
</audio>
<details>
  <summary>Transcript</summary>
  <p>Full transcript text...</p>
</details>

---

Operable

Keyboard accessible (2.1)

All functionality must be keyboard accessible. Prefer native interactive elements — <button>, <a href>, and form controls handle Enter/Space activation, focus, and assistive-tech semantics for free. Only add manual keyboard handling when you cannot use a native element.

<!-- ❌ Non-interactive element with click only: not focusable, no keyboard activation -->
<div class="card" onclick="handleAction()">Open</div>

<!-- ✅ Best: use a native button -->
<button type="button" onclick="handleAction()">Open</button>

// ✅ When you MUST use a non-interactive element (e.g. div with role="button"),
// make it focusable AND handle keyboard activation. Do NOT add this to a native
// <button> — Enter/Space already fire click, so you'd double-trigger.
element.setAttribute('role', 'button');
element.setAttribute('tabindex', '0');
element.addEventListener('click', handleAction);
element.addEventListener('keydown', (e) => {
  if (e.key === 'Enter' || e.key === ' ') {
    e.preventDefault();
    handleAction();
  }
});

No keyboard traps. Users must be able to Tab into and out of every component. Use the modal focus trap pattern for dialogs—the native <dialog> element handles this automatically.

Focus visible (2.4.7)

/* ❌ Never remove focus outlines */
*:focus { outline: none; }

/* ✅ Use :focus-visible for keyboard-only focus */
:focus {
  outline: none;
}

:focus-visible {
  outline: 2px solid currentColor; /* inherits text color → already contrast-checked */
  outline-offset: 2px;
}

/* ✅ Or pick a brand color and verify ≥3:1 contrast against every background it lands on */
button:focus-visible {
  box-shadow: 0 0 0 3px rgba(0, 95, 204, 0.5);
}

Focus not obscured (2.4.11) — new in 2.2

When an element receives keyboard focus, it must not be entirely hidden by other author-created content such as sticky headers, footers, or overlapping panels. At Level AAA (2.4.12), no part of the focused element may be hidden.

/* ✅ Account for sticky headers when scrolling to focused elements */
:target {
  scroll-margin-top: 80px;
}

/* ✅ Ensure focused items clear fixed/sticky bars */
:focus {
  scroll-margin-top: 80px;
  scroll-margin-bottom: 60px;
}

Skip links (2.4.1)

Provide a skip link so keyboard users can bypass repetitive navigation. See the skip link pattern for full markup and styles.

Target size (2.5.8) — new in 2.2

Interactive targets must be at least 24 × 24 CSS pixels (AA). Exceptions: inline text links, elements where the browser controls the size, and targets where a 24px circle centered on the bounding box does not overlap another target.

/* ✅ Minimum target size */
button,
[role="button"],
input[type="checkbox"] + label,
input[type="radio"] + label {
  min-width: 24px;
  min-height: 24px;
}

/* ✅ Comfortable target size (recommended 44×44) */
.touch-target {
  min-width: 44px;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

Dragging movements (2.5.7) — new in 2.2

Any action that requires dragging must have a single-pointer alternative (e.g., buttons, inputs). See the dragging movements pattern for a sortable-list example.

Timing (2.2)

// Allow users to extend time limits
function showSessionWarning() {
  const modal = createModal({
    title: 'Session Expiring',
    content: 'Your session will expire in 2 minutes.',
    actions: [
      { label: 'Extend session', action: extendSession },
      { label: 'Log out', action: logout }
    ],
    timeout: 120000
  });
}

Motion (2.3)

/* Respect reduced motion preference */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

---

Understandable

Page language (3.1.1)

<!-- ❌ No language specified -->
<html>

<!-- ✅ Language specified -->
<html lang="en">

<!-- ✅ Language changes within page -->
<p>The French word for hello is <span lang="fr">bonjour</span>.</p>

Consistent navigation (3.2.3)

<!-- Navigation should be consistent across pages -->
<nav aria-label="Main">
  <ul>
    <li><a href="/" aria-current="page">Home</a></li>
    <li><a href="/products">Products</a></li>
    <li><a href="/about">About</a></li>
  </ul>
</nav>

Consistent help (3.2.6) — new in 2.2

If a help mechanism (contact info, chat widget, FAQ link, self-help option) is repeated across multiple pages, it must appear in the same relative order each time. Users who rely on consistent placement shouldn't have to hunt for help on every page.

Form labels (3.3.2)

Every input needs a programmatically associated label. See the form labels pattern for explicit, implicit, and instructional examples.

Error handling (3.3.1, 3.3.3)

Announce errors to screen readers with role="alert" or aria-live, set aria-invalid="true" on invalid fields, and focus the first error on submit. See the error handling pattern for full markup and JS.

Redundant entry (3.3.7) — new in 2.2

Don't force users to re-enter information they already provided in the same session. Auto-populate from earlier steps, or let users select from previously entered values. Exceptions: security re-confirmation and content that has expired.

<!-- ✅ Auto-fill shipping address from billing -->
<fieldset>
  <legend>Shipping address</legend>
  <label>
    <input type="checkbox" id="same-as-billing" checked>
    Same as billing address
  </label>
  <!-- Fields auto-populated when checked -->
</fieldset>

Accessible authentication (3.3.8) — new in 2.2

Login flows must not rely on cognitive function tests (e.g., remembering a password, solving a puzzle) unless at least one of:

• A copy-paste or autofill mechanism is available
• An alternative method exists (e.g., passkey, SSO, email link)
• The test uses object recognition or personal content (AA only; AAA removes this exception)

<!-- ✅ Allow paste in password fields -->
<input type="password" id="password" autocomplete="current-password">

<!-- ✅ Offer passwordless alternatives -->
<button type="button">Sign in with passkey</button>
<button type="button">Email me a login link</button>

---

Robust

ARIA usage (4.1.2)

Prefer native elements:

<!-- ❌ ARIA role on div -->
<div role="button" tabindex="0">Click me</div>

<!-- ✅ Native button -->
<button>Click me</button>

<!-- ❌ ARIA checkbox -->
<div role="checkbox" aria-checked="false">Option</div>

<!-- ✅ Native checkbox -->
<label><input type="checkbox"> Option</label>

When ARIA is needed, use the correct roles and states. See the ARIA tabs pattern for a complete tablist example.

Live regions (4.1.3)

Use aria-live regions to announce dynamic content changes without moving focus. See the live regions pattern for markup and a showNotification() helper.

---

Testing checklist

Automated testing

# Lighthouse accessibility audit
npx lighthouse https://example.com --only-categories=accessibility

# axe-core
npm install @axe-core/cli -g
axe https://example.com

Manual testing

• [ ] Keyboard navigation: Tab through entire page, use Enter/Space to activate
• [ ] Screen reader: Test with VoiceOver (Mac), NVDA (Windows), or TalkBack (Android)
• [ ] Zoom: Content usable at 200% zoom
• [ ] High contrast: Test with Windows High Contrast Mode
• [ ] Reduced motion: Test with prefers-reduced-motion: reduce
• [ ] Focus order: Logical and follows visual order
• [ ] Target size: Interactive elements meet 24×24px minimum

See the screen reader commands reference for VoiceOver and NVDA shortcuts.

---

Common issues by impact

Critical (fix immediately)

1. Missing form labels 2. Missing image alt text 3. Insufficient color contrast 4. Keyboard traps 5. No focus indicators

Serious (fix before launch)

1. Missing page language 2. Missing heading structure 3. Non-descriptive link text 4. Auto-playing media 5. Missing skip links

Moderate (fix soon)

1. Missing ARIA labels on icons 2. Inconsistent navigation 3. Missing error identification 4. Timing without controls 5. Missing landmark regions

References

• WCAG 2.2 Quick Reference
• WAI-ARIA Authoring Practices
• Deque axe Rules
• Web Quality Audit
• WCAG criteria reference
• Accessibility code patterns

Accessibility Code Patterns

Practical, copy-paste-ready patterns for common accessibility requirements. Each pattern is self-contained and linked from the main SKILL.md.

---

Modal focus trap

Trap keyboard focus inside a modal dialog so Tab/Shift+Tab cycle through its focusable elements and Escape closes it.

function openModal(modal) {
  const focusableElements = modal.querySelectorAll(
    'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
  );
  const firstElement = focusableElements[0];
  const lastElement = focusableElements[focusableElements.length - 1];

  modal.addEventListener('keydown', (e) => {
    if (e.key === 'Tab') {
      if (e.shiftKey && document.activeElement === firstElement) {
        e.preventDefault();
        lastElement.focus();
      } else if (!e.shiftKey && document.activeElement === lastElement) {
        e.preventDefault();
        firstElement.focus();
      }
    }
    if (e.key === 'Escape') {
      closeModal();
    }
  });

  firstElement.focus();
}

The native <dialog> element handles focus trapping automatically—prefer it when browser support allows.

---

Skip link

Allows keyboard users to bypass repetitive navigation and jump straight to main content.

<body>
  <a href="#main-content" class="skip-link">Skip to main content</a>
  <header><!-- navigation --></header>
  <main id="main-content" tabindex="-1">
    <!-- main content -->
  </main>
</body>

.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: #000;
  color: #fff;
  padding: 8px 16px;
  z-index: 100;
}

.skip-link:focus {
  top: 0;
}

---

Error handling

Announce errors to screen readers and focus the first invalid field on submit.

<form novalidate>
  <div class="field" aria-live="polite">
    <label for="email">Email</label>
    <input type="email" id="email"
           aria-invalid="true"
           aria-describedby="email-error">
    <p id="email-error" class="error" role="alert">
      Please enter a valid email address (e.g., name@example.com)
    </p>
  </div>
</form>

form.addEventListener('submit', (e) => {
  const firstError = form.querySelector('[aria-invalid="true"]');
  if (firstError) {
    e.preventDefault();
    firstError.focus();

    const errorSummary = document.getElementById('error-summary');
    errorSummary.textContent =
      `${errors.length} errors found. Please fix them and try again.`;
    errorSummary.focus();
  }
});

---

Form labels

Every input needs an associated label—either explicit (for/id) or implicit (wrapping <label>).

<!-- ❌ No label association -->
<input type="email" placeholder="Email">

<!-- ✅ Explicit label -->
<label for="email">Email address</label>
<input type="email" id="email" name="email"
       autocomplete="email" required>

<!-- ✅ Implicit label -->
<label>
  Email address
  <input type="email" name="email" autocomplete="email" required>
</label>

<!-- ✅ With instructions -->
<label for="password">Password</label>
<input type="password" id="password"
       aria-describedby="password-requirements">
<p id="password-requirements">
  Must be at least 8 characters with one number.
</p>

---

Dragging movements

Any action triggered by dragging must offer a single-pointer alternative (WCAG 2.5.7).

<!-- ❌ Drag-only reorder -->
<ul class="sortable-list" draggable="true">
  <li>Item 1</li>
  <li>Item 2</li>
</ul>

<!-- ✅ Drag + button alternatives -->
<ul class="sortable-list">
  <li>
    <span>Item 1</span>
    <button aria-label="Move Item 1 up">↑</button>
    <button aria-label="Move Item 1 down">↓</button>
  </li>
  <li>
    <span>Item 2</span>
    <button aria-label="Move Item 2 up">↑</button>
    <button aria-label="Move Item 2 down">↓</button>
  </li>
</ul>

Also applies to sliders, map panning, colour pickers, and similar drag-based widgets—always provide an equivalent click/tap or keyboard path.

---

ARIA tabs

Tabs require role="tablist", role="tab", and role="tabpanel" with proper aria-selected, aria-controls, and keyboard support.

<div role="tablist" aria-label="Product information">
  <button role="tab" id="tab-1" aria-selected="true"
          aria-controls="panel-1">Description</button>
  <button role="tab" id="tab-2" aria-selected="false"
          aria-controls="panel-2" tabindex="-1">Reviews</button>
</div>
<div role="tabpanel" id="panel-1" aria-labelledby="tab-1">
  <!-- Panel content -->
</div>
<div role="tabpanel" id="panel-2" aria-labelledby="tab-2" hidden>
  <!-- Panel content -->
</div>

Arrow keys should move focus between tabs; the active tab receives tabindex="0" while inactive tabs use tabindex="-1".

---

Live regions and notifications

Use aria-live to announce dynamic content changes to screen readers without moving focus.

<!-- Status updates (polite — waits for pause in speech) -->
<div aria-live="polite" aria-atomic="true" class="status">
  <!-- Content updates announced to screen readers -->
</div>

<!-- Urgent alerts (assertive — interrupts) -->
<div role="alert" aria-live="assertive">
  <!-- Interrupts current announcement -->
</div>

function showNotification(message, type = 'polite') {
  const container = document.getElementById(`${type}-announcer`);
  container.textContent = '';
  requestAnimationFrame(() => {
    container.textContent = message;
  });
}

Clear the container before writing to ensure the same message triggers a new announcement.

---

Screen reader commands

Quick reference for the most common screen reader shortcuts.

WCAG 2.2 Quick Reference

Success criteria by level

Level A (minimum)

Level AA (standard)

Level AAA (enhanced)

Common ARIA patterns

Buttons

<button>Label</button>
<!-- or -->
<button aria-label="Close dialog">×</button>

Links

<a href="/page">Descriptive link text</a>
<!-- External links -->
<a href="https://external.com" target="_blank" rel="noopener">
  External site
  <span class="visually-hidden">(opens in new tab)</span>
</a>

Form fields

<label for="email">Email address</label>
<input type="email" id="email" aria-describedby="email-hint">
<p id="email-hint">We'll never share your email.</p>

Error states

<label for="email">Email</label>
<input type="email" id="email" aria-invalid="true" aria-describedby="email-error">
<p id="email-error" role="alert">Please enter a valid email address.</p>

Navigation

<nav aria-label="Main">
  <ul>
    <li><a href="/" aria-current="page">Home</a></li>
    <li><a href="/about">About</a></li>
  </ul>
</nav>

Modals

<div role="dialog" aria-modal="true" aria-labelledby="dialog-title">
  <h2 id="dialog-title">Confirm Action</h2>
  <!-- content -->
</div>

Live regions

<!-- Polite (waits for pause in speech) -->
<div aria-live="polite">Status update here</div>

<!-- Assertive (interrupts immediately) -->
<div aria-live="assertive" role="alert">Error message here</div>

<!-- Status (polite, implicit) -->
<div role="status">Loading complete</div>

What changed from 2.1 to 2.2

Testing tools

Sources

• WCAG 2.2 W3C Recommendation
• WCAG 2.2 Quick Reference
• What's New in WCAG 2.2