Accessibility patterns

Accessibility Patterns

Build for everyone from the start.

Core Principles (POUR)

Principle	Meaning	Example
Perceivable	Users can perceive content	Alt text, captions, contrast
Operable	Users can interact	Keyboard access, enough time
Understandable	Users can comprehend	Clear language, predictable
Robust	Works with assistive tech	Valid HTML, ARIA

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WCAG Levels

Level	Description	Target
A	Minimum	Must have
AA	Standard	Industry standard, legal requirement
AAA	Enhanced	Nice to have

Target Level AA for most projects.

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Semantic HTML

Use the Right Element

Instead of	Use
<div onclick>	<button>
<span class="link">	<a href>
<div class="header">	<header>
<div class="nav">	<nav>
<div class="main">	<main>
<b> for emphasis	<strong>
<i> for emphasis	<em>

Document Structure

<!DOCTYPE html>
<html lang="en">
<head>
  <title>Descriptive Page Title</title>
</head>
<body>
  <a href="#main" class="skip-link">Skip to main content</a>
  
  <header>
    <nav aria-label="Main">
      <!-- navigation -->
    </nav>
  </header>
  
  <main id="main">
    <h1>Page Title</h1>
    <!-- Only one h1 per page -->
    
    <article>
      <h2>Section</h2>
      <h3>Subsection</h3>
    </article>
  </main>
  
  <aside aria-label="Related content">
    <!-- sidebar -->
  </aside>
  
  <footer>
    <!-- footer content -->
  </footer>
</body>
</html>

Heading Hierarchy

h1 - Page title (one per page)
  h2 - Major sections
    h3 - Subsections
      h4 - Sub-subsections

Never skip levels (h1 → h3)

---

Images & Media

Alt Text

<!-- Informative image -->
<img src="chart.png" alt="Bar chart showing sales increased 40% in Q4">

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

<!-- Complex image -->
<figure>
  <img src="complex-diagram.png" alt="System architecture diagram">
  <figcaption>
    Detailed description of the system architecture...
  </figcaption>
</figure>

<!-- Image as link -->
<a href="/products">
  <img src="product.jpg" alt="View our products">
</a>

Alt Text Guidelines

Image Type	Alt Text Strategy
Informative	Describe content and function
Decorative	Empty alt=""
Functional	Describe the action
Complex	Brief alt + longer description
Text in image	Include all text

Video & Audio

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

<!-- Audio with transcript -->
<audio controls>
  <source src="podcast.mp3" type="audio/mpeg">
</audio>
<a href="transcript.html">Read transcript</a>

---

Forms

Labels

<!-- Explicit label (preferred) -->
<label for="email">Email address</label>
<input type="email" id="email" name="email">

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

<!-- Required fields -->
<label for="name">
  Name <span aria-hidden="true">*</span>
  <span class="sr-only">(required)</span>
</label>
<input type="text" id="name" required aria-required="true">

Error Handling

<div role="alert" aria-live="polite">
  <p>Please fix the following errors:</p>
  <ul>
    <li><a href="#email">Email is required</a></li>
  </ul>
</div>

<label for="email">Email</label>
<input 
  type="email" 
  id="email" 
  aria-invalid="true"
  aria-describedby="email-error"
>
<span id="email-error" class="error">Please enter a valid email address</span>

Form Groups

<fieldset>
  <legend>Shipping Address</legend>
  
  <label for="street">Street</label>
  <input type="text" id="street">
  
  <label for="city">City</label>
  <input type="text" id="city">
</fieldset>

---

Keyboard Navigation

Focus Management

/* Never remove focus outline without replacement */
:focus {
  outline: 2px solid #005fcc;
  outline-offset: 2px;
}

/* Custom focus style */
:focus-visible {
  outline: 3px solid #005fcc;
  outline-offset: 2px;
}

/* Hide outline for mouse users */
:focus:not(:focus-visible) {
  outline: none;
}

Tab Order

<!-- Natural tab order follows DOM order -->
<!-- Use tabindex only when necessary -->

<button>First</button>
<button>Second</button>
<button>Third</button>

<!-- tabindex="0" - adds to tab order -->
<div tabindex="0" role="button">Custom interactive element</div>

<!-- tabindex="-1" - focusable via JS, not tab -->
<div tabindex="-1" id="modal">Modal content</div>

<!-- Never use tabindex > 0 -->

Skip Links

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

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

.skip-link:focus {
  top: 0;
}
</style>

Keyboard Patterns

Component	Keys
Buttons	Enter, Space
Links	Enter
Menus	Arrows, Enter, Escape
Tabs	Arrows, Tab
Modals	Tab (trapped), Escape to close

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ARIA

When to Use ARIA

1. First, use semantic HTML
2. Then, add ARIA if needed
3. "No ARIA is better than bad ARIA"

Common ARIA Patterns

<!-- Live regions (for dynamic content) -->
<div aria-live="polite">Content updates will be announced</div>
<div aria-live="assertive">Urgent updates interrupt</div>

<!-- Expanded/collapsed -->
<button aria-expanded="false" aria-controls="menu">Menu</button>
<ul id="menu" hidden>...</ul>

<!-- Current page -->
<nav>
  <a href="/" aria-current="page">Home</a>
  <a href="/about">About</a>
</nav>

<!-- Busy state -->
<div aria-busy="true">Loading...</div>

<!-- Hidden from AT -->
<span aria-hidden="true">👍</span>

<!-- Labels -->
<button aria-label="Close">×</button>
<nav aria-label="Main navigation">...</nav>
<section aria-labelledby="section-heading">
  <h2 id="section-heading">Section Title</h2>
</section>

ARIA Roles

<!-- Landmarks -->
<div role="banner">Header</div>
<div role="navigation">Nav</div>
<div role="main">Main</div>
<div role="complementary">Sidebar</div>
<div role="contentinfo">Footer</div>

<!-- Widgets -->
<div role="button">Custom button</div>
<div role="dialog" aria-modal="true">Modal</div>
<div role="tablist">Tabs</div>
<div role="alert">Error message</div>

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Color & Contrast

Contrast Requirements

Text Size	Level AA	Level AAA
Normal text (<18px)	4.5:1	7:1
Large text (≥18px bold, ≥24px)	3:1	4.5:1
UI components	3:1	-

Color Independence

<!-- Don't rely on color alone -->

<!-- Bad -->
<span style="color: red">Error</span>

<!-- Good -->
<span style="color: red">
  ⚠️ Error: <span class="error-text">Please enter a valid email</span>
</span>

Testing Tools

• WebAIM Contrast Checker
• Chrome DevTools color picker
• Stark (Figma plugin)
• axe DevTools

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Testing

Automated Testing

// Using jest-axe
import { axe, toHaveNoViolations } from 'jest-axe';

expect.extend(toHaveNoViolations);

it('should have no accessibility violations', async () => {
  const { container } = render(<MyComponent />);
  const results = await axe(container);
  expect(results).toHaveNoViolations();
});

Manual Testing Checklist

• Navigate entire page with keyboard only
• Test with screen reader (VoiceOver, NVDA)
• Check color contrast
• Zoom to 200% - still usable?
• Disable CSS - still understandable?
• Check all images have alt text
• Verify form labels and errors
• Test focus visibility
• Check heading structure

Screen Reader Testing

OS	Screen Reader	Browser
macOS	VoiceOver	Safari
Windows	NVDA	Firefox
Windows	JAWS	Chrome
Mobile	TalkBack	Chrome
iOS	VoiceOver	Safari

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Common Patterns

Modal Dialog

<div 
  role="dialog" 
  aria-modal="true" 
  aria-labelledby="dialog-title"
  aria-describedby="dialog-desc"
>
  <h2 id="dialog-title">Confirm Action</h2>
  <p id="dialog-desc">Are you sure you want to proceed?</p>
  
  <button>Cancel</button>
  <button>Confirm</button>
</div>

Focus management:

1. Move focus to modal on open
2. Trap focus inside modal
3. Return focus to trigger on close

Tabs

<div role="tablist" aria-label="Settings">
  <button role="tab" aria-selected="true" aria-controls="panel-1" id="tab-1">
    General
  </button>
  <button role="tab" aria-selected="false" aria-controls="panel-2" id="tab-2">
    Security
  </button>
</div>

<div role="tabpanel" id="panel-1" aria-labelledby="tab-1">
  General settings content
</div>
<div role="tabpanel" id="panel-2" aria-labelledby="tab-2" hidden>
  Security settings content
</div>

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References

• references/wcag-checklist.md - Full WCAG 2.1 checklist
• references/aria-patterns.md - Common ARIA patterns
• references/testing-tools.md - Testing tool setup