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)