accessibility-checker

Accessibility Checker

Validate web accessibility and ensure WCAG compliance.

Quick Start

Use semantic HTML, add ARIA labels, ensure keyboard navigation, test color contrast, validate with axe or Lighthouse.

Instructions

WCAG Compliance Levels

Level A (minimum):

• Basic accessibility
• Must meet for legal compliance

Level AA (recommended):

• Standard for most websites
• Includes contrast requirements
• Government sites requirement

Level AAA (enhanced):

• Highest level
• Not required for all content
• Best practices

Common Accessibility Issues

1. Missing alt text:

// Bad
<img src="logo.png" />

// Good
<img src="logo.png" alt="Company Logo" />

// Decorative images
<img src="decoration.png" alt="" />

2. Poor color contrast:

/* Bad: 2.5:1 contrast */
color: #777;
background: #fff;

/* Good: 4.5:1 contrast (AA) */
color: #595959;
background: #fff;

/* Better: 7:1 contrast (AAA) */
color: #333;
background: #fff;

3. Missing form labels:

// Bad
<input type="text" placeholder="Name" />

// Good
<label htmlFor="name">Name</label>
<input type="text" id="name" />

// Or with aria-label
<input type="text" aria-label="Name" />

4. No keyboard navigation:

// Bad: onClick on div
<div onClick={handleClick}>Click me</div>

// Good: Use button
<button onClick={handleClick}>Click me</button>

// Or make div focusable
<div
  role="button"
  tabIndex={0}
  onClick={handleClick}
  onKeyPress={(e) => e.key === 'Enter' && handleClick()}
>
  Click me
</div>

5. Missing ARIA labels:

// Bad: Icon button without label
<button><CloseIcon /></button>

// Good: Add aria-label
<button aria-label="Close dialog">
  <CloseIcon />
</button>

Semantic HTML

Use proper elements:

// Bad
<div onClick={handleClick}>Submit</div>

// Good
<button onClick={handleClick}>Submit</button>

// Bad
<div className="heading">Title</div>

// Good
<h1>Title</h1>

Heading hierarchy:

// Bad: Skipping levels
<h1>Page Title</h1>
<h3>Section</h3>

// Good: Proper hierarchy
<h1>Page Title</h1>
<h2>Section</h2>
<h3>Subsection</h3>

Landmarks:

<header>
  <nav aria-label="Main navigation">
    {/* Navigation links */}
  </nav>
</header>

<main>
  <article>
    {/* Main content */}
  </article>
  <aside>
    {/* Sidebar */}
  </aside>
</main>

<footer>
  {/* Footer content */}
</footer>

ARIA Attributes

aria-label:

<button aria-label="Close">
  <X />
</button>

aria-labelledby:

<h2 id="dialog-title">Confirm Action</h2>
<div role="dialog" aria-labelledby="dialog-title">
  {/* Dialog content */}
</div>

aria-describedby:

<input
  type="password"
  aria-describedby="password-hint"
/>
<span id="password-hint">
  Must be at least 8 characters
</span>

aria-live:

// Announce updates to screen readers
<div aria-live="polite" aria-atomic="true">
  {statusMessage}
</div>

// For urgent updates
<div aria-live="assertive">
  {errorMessage}
</div>

aria-expanded:

<button
  aria-expanded={isOpen}
  aria-controls="menu"
  onClick={toggleMenu}
>
  Menu
</button>
<div id="menu" hidden={!isOpen}>
  {/* Menu items */}
</div>

Keyboard Navigation

Tab order:

// Use tabIndex to control focus order
<button tabIndex={0}>First</button>
<button tabIndex={0}>Second</button>
<button tabIndex={-1}>Not in tab order</button>

Focus management:

function Dialog({ onClose }) {
  const closeButtonRef = useRef();
  
  useEffect(() => {
    // Focus close button when dialog opens
    closeButtonRef.current?.focus();
    
    // Trap focus in dialog
    const handleTab = (e) => {
      if (e.key === 'Tab') {
        // Implement focus trap
      }
    };
    
    document.addEventListener('keydown', handleTab);
    return () => document.removeEventListener('keydown', handleTab);
  }, []);
  
  return (
    <div role="dialog" aria-modal="true">
      <button ref={closeButtonRef} onClick={onClose}>
        Close
      </button>
    </div>
  );
}

Keyboard shortcuts:

useEffect(() => {
  const handleKeyPress = (e) => {
    if (e.key === 'Escape') {
      closeDialog();
    }
    if (e.key === '/' && e.ctrlKey) {
      openSearch();
    }
  };
  
  document.addEventListener('keydown', handleKeyPress);
  return () => document.removeEventListener('keydown', handleKeyPress);
}, []);

Screen Reader Support

Skip links:

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

<main id="main-content">
  {/* Content */}
</main>

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

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

Visually hidden text:

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

// Usage
<button>
  <TrashIcon />
  <span className="sr-only">Delete item</span>
</button>

Announce dynamic content:

function Toast({ message }) {
  return (
    <div
      role="status"
      aria-live="polite"
      aria-atomic="true"
    >
      {message}
    </div>
  );
}

Color Contrast

Check contrast ratios:

• Normal text: 4.5:1 (AA), 7:1 (AAA)
• Large text (18pt+): 3:1 (AA), 4.5:1 (AAA)
• UI components: 3:1

Tools:

• WebAIM Contrast Checker
• Chrome DevTools
• Lighthouse

Don't rely on color alone:

// Bad: Only color indicates error
<input style={{ borderColor: 'red' }} />

// Good: Color + icon + text
<div>
  <input aria-invalid="true" aria-describedby="error" />
  <span id="error">
    <ErrorIcon /> Email is required
  </span>
</div>

Forms Accessibility

Labels:

<label htmlFor="email">Email</label>
<input
  type="email"
  id="email"
  required
  aria-required="true"
/>

Error messages:

<input
  type="email"
  aria-invalid={hasError}
  aria-describedby={hasError ? "email-error" : undefined}
/>
{hasError && (
  <span id="email-error" role="alert">
    Please enter a valid email
  </span>
)}

Fieldsets:

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

Testing Tools

Automated testing:

# Install axe-core
npm install --save-dev @axe-core/react

# Use in tests
import { axe, toHaveNoViolations } from 'jest-axe';
expect.extend(toHaveNoViolations);

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

Browser extensions:

• axe DevTools
• WAVE
• Lighthouse

Screen readers:

• NVDA (Windows, free)
• JAWS (Windows)
• VoiceOver (Mac, built-in)
• TalkBack (Android)

Common Patterns

Modal dialog:

function Modal({ isOpen, onClose, title, children }) {
  const modalRef = useRef();
  
  useEffect(() => {
    if (isOpen) {
      modalRef.current?.focus();
      document.body.style.overflow = 'hidden';
    }
    return () => {
      document.body.style.overflow = '';
    };
  }, [isOpen]);
  
  if (!isOpen) return null;
  
  return (
    <div
      role="dialog"
      aria-modal="true"
      aria-labelledby="modal-title"
      ref={modalRef}
      tabIndex={-1}
    >
      <h2 id="modal-title">{title}</h2>
      {children}
      <button onClick={onClose} aria-label="Close dialog">
        Close
      </button>
    </div>
  );
}

Dropdown menu:

function Dropdown({ label, items }) {
  const [isOpen, setIsOpen] = useState(false);
  
  return (
    <div>
      <button
        aria-haspopup="true"
        aria-expanded={isOpen}
        onClick={() => setIsOpen(!isOpen)}
      >
        {label}
      </button>
      {isOpen && (
        <ul role="menu">
          {items.map(item => (
            <li key={item.id} role="menuitem">
              <button onClick={item.onClick}>
                {item.label}
              </button>
            </li>
          ))}
        </ul>
      )}
    </div>
  );
}

Tabs:

function Tabs({ tabs }) {
  const [activeTab, setActiveTab] = useState(0);
  
  return (
    <div>
      <div role="tablist">
        {tabs.map((tab, index) => (
          <button
            key={tab.id}
            role="tab"
            aria-selected={activeTab === index}
            aria-controls={`panel-${tab.id}`}
            onClick={() => setActiveTab(index)}
          >
            {tab.label}
          </button>
        ))}
      </div>
      {tabs.map((tab, index) => (
        <div
          key={tab.id}
          role="tabpanel"
          id={`panel-${tab.id}`}
          hidden={activeTab !== index}
        >
          {tab.content}
        </div>
      ))}
    </div>
  );
}

Accessibility Checklist

Perceivable:

• All images have alt text
• Color contrast meets WCAG AA (4.5:1)
• Text can be resized to 200%
• Content is not conveyed by color alone

Operable:

• All functionality available via keyboard
• No keyboard traps
• Skip links provided
• Focus indicators visible

Understandable:

• Page language specified
• Labels for form inputs
• Error messages clear
• Consistent navigation

Robust:

• Valid HTML
• ARIA used correctly
• Works with assistive technologies
• No console errors

Best Practices

Start accessible:

• Use semantic HTML first
• Add ARIA only when needed
• Test with keyboard
• Test with screen reader

Progressive enhancement:

• Core functionality works without JS
• Enhanced experience with JS
• Graceful degradation

Regular testing:

• Automated tests (axe)
• Manual keyboard testing
• Screen reader testing
• User testing with disabled users