# Accessibility Design

> WCAG 2.1 AA compliance patterns, screen reader compatibility, keyboard navigation, and ARIA best practices. Use when implementing accessible interfaces, reviewing UI components, or auditing accessibility compliance. Covers semantic HTML, focus management, color contrast, and assistive technology testing.

- Skill: `diegosouzapw/accessibility-design` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add diegosouzapw/accessibility-design`
- Raw SKILL.md: https://api.skillmd.com/api/skills/diegosouzapw/accessibility-design/raw
- Safety review: pending (external: skill-scanner PASS, skillspector CAUTION)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- License: MIT
- Author: diegosouzapw (https://skillmd.com/u/diegosouzapw)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/diegosouzapw/accessibility-design

---


# Accessibility Design

Roleplay as an accessibility specialist providing comprehensive guidance for implementing WCAG 2.1 AA compliance across digital products. Establishes patterns for semantic markup, assistive technology compatibility, and inclusive interaction design.

AccessibilityDesign {
  Activation {
    Implementing accessible user interfaces
    Reviewing UI components for accessibility compliance
    Auditing WCAG 2.1 AA compliance
    Designing keyboard navigation patterns
    Implementing ARIA for custom widgets
    Testing with screen readers and assistive technologies
    Ensuring color contrast and visual accessibility
  }

  Constraints {
    1. Semantic HTML first - ARIA should enhance, never replace proper markup
    2. Use native HTML elements whenever possible
    3. Never remove focus indicators entirely
    4. Never rely on color alone to convey information
    5. All functionality must be keyboard accessible
    6. Maintain logical heading order without skipping levels
  }

  POURFramework {
    Description: "All accessibility work follows the four POUR principles"

    Perceivable {
      Provide text alternatives for non-text content
      Create content adaptable to different presentations
      Make content distinguishable (color, contrast, audio control)
    }

    Operable {
      Make all functionality keyboard accessible
      Provide sufficient time to read and use content
      Avoid content that causes seizures or physical reactions
      Help users navigate, find content, and determine location
    }

    Understandable {
      Make text readable and understandable
      Make pages appear and operate predictably
      Help users avoid and correct mistakes
    }

    Robust {
      Maximize compatibility with current and future assistive technologies
      Use valid, semantic markup
      Ensure programmatic access to all functionality
    }
  }

  SemanticHTMLFirst {
    Correct {
      ```html
      <button type="submit">Submit Form</button>
      ```
    }

    Incorrect {
      ```html
      <div role="button" tabindex="0" onclick="submit()">Submit Form</div>
      ```
    }

    NativeElements {
      `<button>` for actions
      `<a href>` for navigation
      `<input>`, `<select>`, `<textarea>` for form controls
      `<nav>`, `<main>`, `<aside>`, `<header>`, `<footer>` for landmarks
      `<h1>` through `<h6>` for heading hierarchy
    }
  }

  ProgressiveEnhancement {
    1. Semantic HTML provides baseline accessibility
    2. CSS enhances presentation without breaking structure
    3. JavaScript adds interactivity while maintaining keyboard access
    4. ARIA fills gaps for complex widgets not covered by HTML
  }

  ImplementationPatterns {
    DocumentStructure {
      ```html
      <!DOCTYPE html>
      <html lang="en">
      <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Descriptive Page Title - Site Name</title>
      </head>
      <body>
        <a href="#main-content" class="skip-link">Skip to main content</a>

        <header role="banner">
          <nav aria-label="Main navigation">
            <!-- Navigation content -->
          </nav>
        </header>

        <main id="main-content" role="main">
          <h1>Page Heading</h1>
          <!-- Page content -->
        </main>

        <footer role="contentinfo">
          <!-- Footer content -->
        </footer>
      </body>
      </html>
      ```
    }

    HeadingHierarchy {
      ```html
      <h1>Main Page Title</h1>
        <h2>Section Title</h2>
          <h3>Subsection Title</h3>
          <h3>Another Subsection</h3>
        <h2>Another Section</h2>
          <h3>Subsection</h3>
            <h4>Sub-subsection</h4>
      ```
    }

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

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

  FocusManagement {
    VisibleFocusIndicators {
      ```css
      :focus {
        outline: 2px solid #005fcc;
        outline-offset: 2px;
      }

      /* Enhanced focus for better visibility */
      :focus-visible {
        outline: 3px solid #005fcc;
        outline-offset: 3px;
        box-shadow: 0 0 0 6px rgba(0, 95, 204, 0.25);
      }

      /* Never remove focus indicators entirely */
      :focus:not(:focus-visible) {
        outline: 2px solid transparent;
        box-shadow: 0 0 0 2px #005fcc;
      }
      ```
    }

    FocusTrappingForModals {
      ```javascript
      function trapFocus(element) {
        const focusableElements = element.querySelectorAll(
          'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
        );
        const firstFocusable = focusableElements[0];
        const lastFocusable = focusableElements[focusableElements.length - 1];

        element.addEventListener('keydown', (e) => {
          if (e.key !== 'Tab') return;

          if (e.shiftKey) {
            if (document.activeElement === firstFocusable) {
              lastFocusable.focus();
              e.preventDefault();
            }
          } else {
            if (document.activeElement === lastFocusable) {
              firstFocusable.focus();
              e.preventDefault();
            }
          }
        });
      }
      ```
    }
  }

  KeyboardNavigation {
    StandardPatterns {
      | Key | Action |
      |-----|--------|
      | Tab | Move focus to next focusable element |
      | Shift+Tab | Move focus to previous focusable element |
      | Enter/Space | Activate buttons and links |
      | Arrow keys | Navigate within components (menus, tabs, radio groups) |
      | Escape | Close modals, menus, dropdowns |
      | Home/End | Move to first/last item in lists |
    }

    TabOrder {
      ```html
      <!-- Correct: Tab order matches visual order -->
      <form>
        <label for="name">Name</label>
        <input id="name" type="text">

        <label for="email">Email</label>
        <input id="email" type="email">

        <button type="submit">Submit</button>
      </form>
      ```

      Rules {
        Never use positive `tabindex` values
        Use `tabindex="0"` to make non-interactive elements focusable
        Use `tabindex="-1"` to make elements programmatically focusable but not in tab order
      }
    }
  }

  ARIAPatterns {
    WhenToUseARIA {
      Custom widgets: Tabs, accordions, carousels, tree views
      Dynamic content: Live regions for updates
      Relationships: Connecting labels to complex controls
      States: Expanded/collapsed, selected, pressed
    }

    ARIARoles {
      ```html
      <!-- Tab pattern -->
      <div role="tablist" aria-label="Settings tabs">
        <button role="tab" aria-selected="true" aria-controls="panel1" id="tab1">
          General
        </button>
        <button role="tab" aria-selected="false" aria-controls="panel2" id="tab2">
          Security
        </button>
      </div>
      <div role="tabpanel" id="panel1" aria-labelledby="tab1">
        <!-- Panel content -->
      </div>
      <div role="tabpanel" id="panel2" aria-labelledby="tab2" hidden>
        <!-- Panel content -->
      </div>
      ```
    }

    ARIAStatesAndProperties {
      | Attribute | Purpose | Example |
      |-----------|---------|---------|
      | `aria-expanded` | Indicates expandable element state | `aria-expanded="false"` |
      | `aria-selected` | Indicates selection state | `aria-selected="true"` |
      | `aria-pressed` | Indicates toggle button state | `aria-pressed="mixed"` |
      | `aria-hidden` | Hides content from assistive tech | `aria-hidden="true"` |
      | `aria-live` | Announces dynamic content | `aria-live="polite"` |
      | `aria-describedby` | References descriptive content | `aria-describedby="hint"` |
      | `aria-labelledby` | References labeling content | `aria-labelledby="heading"` |
    }

    LiveRegions {
      ```html
      <!-- Polite: Announces when user is idle -->
      <div aria-live="polite" aria-atomic="true">
        Form saved successfully
      </div>

      <!-- Assertive: Interrupts immediately (use sparingly) -->
      <div aria-live="assertive" role="alert">
        Error: Please correct the highlighted fields
      </div>

      <!-- Status messages -->
      <div role="status">
        Loading... 50% complete
      </div>
      ```
    }
  }

  FormAccessibility {
    LabelsAndInstructions {
      ```html
      <!-- Explicit label association -->
      <label for="username">Username</label>
      <input type="text" id="username" name="username"
             aria-describedby="username-hint">
      <span id="username-hint">Must be 3-20 characters</span>

      <!-- Grouped controls with fieldset -->
      <fieldset>
        <legend>Shipping Address</legend>
        <label for="street">Street</label>
        <input type="text" id="street">
        <!-- More fields -->
      </fieldset>
      ```
    }

    ErrorHandling {
      ```html
      <label for="email">Email</label>
      <input type="email" id="email"
             aria-invalid="true"
             aria-describedby="email-error">
      <span id="email-error" role="alert">
        Please enter a valid email address (example: user@domain.com)
      </span>
      ```

      Requirements {
        Identify the field in error
        Describe what went wrong
        Provide guidance for correction
        Use `aria-invalid` on the field
        Announce errors via live region or `role="alert"`
      }
    }

    RequiredFields {
      ```html
      <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">
      ```
    }
  }

  ImagesAndMedia {
    AlternativeText {
      ```html
      <!-- Informative image -->
      <img src="chart.png" alt="Q3 revenue increased 15% compared to Q2">

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

      <!-- Complex image with extended description -->
      <figure>
        <img src="flowchart.png" alt="User registration process"
             aria-describedby="flowchart-desc">
        <figcaption id="flowchart-desc">
          The registration process begins with email verification,
          followed by profile creation, and ends with account activation.
        </figcaption>
      </figure>
      ```
    }

    VideoAndAudio {
      ```html
      <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>
      ```
    }
  }

  ColorAndContrast {
    MinimumContrastRatios {
      | Content Type | Minimum Ratio (AA) | Enhanced Ratio (AAA) |
      |--------------|-------------------|---------------------|
      | Normal text (< 18pt) | 4.5:1 | 7:1 |
      | Large text (>= 18pt or 14pt bold) | 3:1 | 4.5:1 |
      | UI components and graphics | 3:1 | N/A |
    }

    NeverRelyOnColorAlone {
      ```html
      <!-- Bad: Color only indicates error -->
      <input style="border-color: red">

      <!-- Good: Color plus icon and text -->
      <input aria-invalid="true" aria-describedby="error">
      <span id="error">
        <svg aria-hidden="true"><!-- Error icon --></svg>
        Invalid email format
      </span>
      ```
    }
  }

  MotionAndAnimation {
    RespectUserPreferences {
      ```css
      /* Reduce motion for users who prefer it */
      @media (prefers-reduced-motion: reduce) {
        *,
        *::before,
        *::after {
          animation-duration: 0.01ms !important;
          animation-iteration-count: 1 !important;
          transition-duration: 0.01ms !important;
        }
      }
      ```
    }

    AutoPlayingContent {
      Avoid auto-playing video or audio
      Provide controls to pause, stop, or hide moving content
      Limit animations to under 5 seconds or provide stop mechanism
    }
  }

  TestingMethodology {
    AutomatedTesting {
      Tools {
        axe DevTools: Browser extension for page analysis
        WAVE: Web accessibility evaluation tool
        Lighthouse: Chrome DevTools accessibility audit
        pa11y: Command-line accessibility testing
      }

      Note: "Automated testing catches approximately 30-40% of issues"
    }

    KeyboardTesting {
      1. Disconnect or disable mouse
      2. Navigate entire page using Tab/Shift+Tab
      3. Verify all interactive elements are reachable
      4. Verify focus indicators are visible
      5. Test all keyboard shortcuts
      6. Escape from all modals and menus
    }

    ScreenReaderTesting {
      Platforms {
        | Platform | Screen Reader | Browser |
        |----------|---------------|---------|
        | Windows | NVDA (free) | Firefox, Chrome |
        | Windows | JAWS | Chrome, Edge |
        | macOS | VoiceOver | Safari |
        | iOS | VoiceOver | Safari |
        | Android | TalkBack | Chrome |
      }

      Checklist {
        All images have appropriate alt text
        Headings convey page structure
        Links and buttons have descriptive names
        Form fields have labels
        Error messages are announced
        Dynamic content updates are announced
        Tables have proper headers
        Custom widgets announce state changes
      }
    }

    VisualTesting {
      Zoom to 200% and verify no horizontal scrolling
      Test with high contrast mode enabled
      Disable images and verify content is still understandable
      Test with browser text size increased
    }
  }

  CommonPatterns {
    ModalDialog {
      ```html
      <div role="dialog" aria-modal="true" aria-labelledby="dialog-title">
        <h2 id="dialog-title">Confirm Action</h2>
        <p>Are you sure you want to proceed?</p>
        <button type="button">Cancel</button>
        <button type="button">Confirm</button>
      </div>
      ```

      Requirements {
        Focus moves to dialog when opened
        Focus is trapped within dialog
        Escape key closes dialog
        Focus returns to trigger element on close
      }
    }

    Accordion {
      ```html
      <div class="accordion">
        <h3>
          <button aria-expanded="true" aria-controls="section1">
            Section 1
          </button>
        </h3>
        <div id="section1" role="region" aria-labelledby="section1-heading">
          <!-- Content -->
        </div>
      </div>
      ```
    }

    NavigationMenu {
      ```html
      <nav aria-label="Main">
        <ul>
          <li><a href="/" aria-current="page">Home</a></li>
          <li>
            <button aria-expanded="false" aria-haspopup="true">
              Products
            </button>
            <ul>
              <li><a href="/products/a">Product A</a></li>
              <li><a href="/products/b">Product B</a></li>
            </ul>
          </li>
        </ul>
      </nav>
      ```
    }

    DataTable {
      ```html
      <table>
        <caption>Q3 Sales by Region</caption>
        <thead>
          <tr>
            <th scope="col">Region</th>
            <th scope="col">Units Sold</th>
            <th scope="col">Revenue</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <th scope="row">North</th>
            <td>1,234</td>
            <td>$45,678</td>
          </tr>
        </tbody>
      </table>
      ```
    }
  }
}

## Resources

- [WCAG 2.1 Guidelines](https://www.w3.org/WAI/WCAG21/quickref/)
- [WAI-ARIA Authoring Practices](https://www.w3.org/WAI/ARIA/apg/)
- [Inclusive Components](https://inclusive-components.design/)
- [A11y Project Checklist](https://www.a11yproject.com/checklist/)