A11y aria patterns

ARIA Patterns and Authoring Practices

Skill type: Reference. This is teaching/pattern content — it explains the WAI-ARIA APG keyboard contracts and ARIA state rules for custom widgets. It is not a scanner. For static review of existing ARIA usage, use /a11y-review. For runtime verification of ARIA validity against resolved roles, use the a11y-testing skill to set up real axe.

ARIA (Accessible Rich Internet Applications) extends HTML semantics for custom, dynamic UI components. It supplements — never replaces — native HTML.

The ARIA First Principles:

1. No ARIA is better than bad ARIA. Incorrect ARIA is worse than no ARIA.
2. Native HTML first. Use a <button> before role="button". Use <select> before a custom combobox.
3. You own the keyboard. Using an ARIA widget role means you are fully responsible for its keyboard behavior per the APG spec.
4. Keep states synchronized. Every ARIA state attribute must reflect the current UI state — never hardcode them.

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ARIA Fundamentals

How ARIA Works

ARIA adds three things to elements in the accessibility tree:

• Roles — what the element is (role="dialog", role="tab")
• Properties — static characteristics (aria-label, aria-required)
• States — dynamic, changing values (aria-expanded, aria-checked, aria-invalid)

Accessible Names (WCAG 4.1.2)

Every interactive element needs an accessible name. The browser computes it in this priority order:

1. aria-labelledby (references another element's text — highest priority)
2. aria-label (inline text string)
3. Native label element (<label for="id">)
4. Element's own text content (for buttons and links)
5. title attribute (last resort — inconsistent screen reader support)

<!-- Priority 1: aria-labelledby -->
<h2 id="section-title">Billing Address</h2>
<section aria-labelledby="section-title">...</section>

<!-- Priority 2: aria-label (when no visible text exists) -->
<button aria-label="Close dialog">
  <svg aria-hidden="true">...</svg>
</button>

<!-- Priority 3: Associated label -->
<label for="card-number">Card Number</label>
<input id="card-number" type="text">

<!-- Priority 4: Button text -->
<button>Submit Order</button>

Accessible Descriptions

aria-describedby provides supplementary information — announced after the name, often as a separate speech unit:

<label for="password">Password</label>
<input
  id="password"
  type="password"
  aria-describedby="password-hint password-error"
>
<p id="password-hint">Must be at least 8 characters.</p>
<p id="password-error" aria-live="polite"></p>

Multiple IDs in aria-describedby are read in order.

---

Common Widget Patterns (APG)

Dialog / Modal (role="dialog")

<!-- Background content inert when modal open -->
<main inert aria-hidden="true">...</main>

<div
  role="dialog"
  aria-modal="true"
  aria-labelledby="dialog-title"
  aria-describedby="dialog-desc"
>
  <h2 id="dialog-title">Confirm Deletion</h2>
  <p id="dialog-desc">This action cannot be undone.</p>

  <button type="button">Cancel</button>
  <button type="button">Delete</button>
</div>

Required behavior:

• On open: Move focus inside the dialog (first focusable element or the dialog itself)
• While open: Trap Tab and Shift+Tab within the dialog
• On Escape: Close dialog, return focus to the trigger element
• On close: Return focus to the element that opened the dialog

role="alertdialog" — for urgent dialogs requiring immediate response (e.g., unsaved changes warning). Screen readers interrupt current speech to announce it.

Tabs Pattern (WCAG 2.1.1)

<div role="tablist" aria-label="Settings Sections">
  <button role="tab" aria-selected="true"  aria-controls="panel-general" id="tab-general">General</button>
  <button role="tab" aria-selected="false" aria-controls="panel-security" id="tab-security" tabindex="-1">Security</button>
  <button role="tab" aria-selected="false" aria-controls="panel-billing"  id="tab-billing"  tabindex="-1">Billing</button>
</div>

<div role="tabpanel" id="panel-general"  aria-labelledby="tab-general">...</div>
<div role="tabpanel" id="panel-security" aria-labelledby="tab-security" hidden>...</div>
<div role="tabpanel" id="panel-billing"  aria-labelledby="tab-billing"  hidden>...</div>

Keyboard behavior (roving tabindex):

Key	Action
Tab	Enter tablist on active tab; Tab again exits to tabpanel
→ / ←	Move to next/previous tab (wraps); auto-activates tab
Home	Move to first tab
End	Move to last tab
Enter / Space	Activate tab (manual activation variant)

Roving tabindex: Only the active tab has tabindex="0". All others have tabindex="-1". JavaScript updates both on navigation.

Accordion / Disclosure (aria-expanded)

<h3>
  <button
    type="button"
    aria-expanded="false"
    aria-controls="faq-1-content"
    id="faq-1-btn"
  >
    What is your return policy?
  </button>
</h3>
<div id="faq-1-content" role="region" aria-labelledby="faq-1-btn" hidden>
  <p>You may return items within 30 days...</p>
</div>

Rules:

• aria-expanded="true/false" on the trigger button — must be JS-driven, never hardcoded
• aria-controls links button to its panel (ID reference)
• Wrap in heading element for document outline
• hidden / aria-hidden="true" on collapsed panels

Combobox / Autocomplete

<label for="country-input">Country</label>
<div role="combobox"
     aria-expanded="false"
     aria-haspopup="listbox"
     aria-owns="country-listbox">
  <input
    id="country-input"
    type="text"
    autocomplete="off"
    aria-autocomplete="list"
    aria-controls="country-listbox"
    aria-activedescendant=""
  >
</div>
<ul id="country-listbox" role="listbox" aria-label="Countries">
  <li role="option" id="opt-us" aria-selected="false">United States</li>
  <li role="option" id="opt-ca" aria-selected="false">Canada</li>
</ul>

Keyboard behavior:

Key	Action
↓	Open list, move to first option
↑ / ↓	Navigate options
Enter	Select focused option
Escape	Close list
Home / End	Jump to first/last option

Update aria-activedescendant on the input to the ID of the currently highlighted option.

Menu / Menubar (role="menu")

Use role="menu" for application menus (File, Edit, View), NOT for navigation. Use <nav> + <ul> for site navigation.

<button
  type="button"
  aria-haspopup="menu"
  aria-expanded="false"
  aria-controls="actions-menu"
  id="actions-btn"
>
  Actions ▾
</button>
<ul role="menu" id="actions-menu" aria-labelledby="actions-btn">
  <li role="menuitem"><button type="button">Edit</button></li>
  <li role="menuitem"><button type="button">Duplicate</button></li>
  <li role="separator"></li>
  <li role="menuitem" aria-disabled="true"><button type="button" disabled>Archive</button></li>
  <li role="menuitem"><button type="button">Delete</button></li>
</ul>

Keyboard behavior:

Key	Action
↓ / ↑	Navigate items (wraps)
Enter / Space	Activate item
Escape	Close menu, return focus to trigger
Home / End	Jump to first/last item
A–Z	Type-ahead selection

---

ARIA Live Regions

Live regions announce dynamic content changes to screen readers without requiring a focus move.

aria-live Values

Value	Behavior	Use For
polite	Waits for user to finish current action	Status updates, form feedback, search results loading
assertive	Interrupts immediately	Critical errors, urgent alerts
off (default)	No announcement	Most content

<!-- Status messages (polite) -->
<div role="status" aria-live="polite" aria-atomic="true">
  <!-- Inject text here when status changes -->
</div>

<!-- Error alerts (assertive) -->
<div role="alert" aria-live="assertive">
  <!-- Inject critical error message here -->
</div>

Semantic Shortcuts

• role="alert" = implicit aria-live="assertive" + aria-atomic="true"
• role="status" = implicit aria-live="polite" + aria-atomic="true"
• role="log" = implicit aria-live="polite" for sequential messages (chat, audit trail)
• role="timer" = implicit aria-live="off" — only announce value when directly focused

Live Region Patterns

Toast notifications:

<!-- Single persistent container in DOM; inject/clear text dynamically -->
<div id="toast-region" role="status" aria-live="polite" aria-atomic="true" class="sr-only">
  <!-- JS sets textContent here; empty string clears it -->
</div>

Loading state:

<div aria-busy="true" aria-live="polite">
  <p>Loading search results...</p>
</div>
<!-- When complete, set aria-busy="false" and replace content -->

Form error summary:

<div role="alert" aria-live="assertive" id="error-summary">
  <!-- Inject on submit: "3 errors found. Please correct: Email is required, ..." -->
</div>

Critical rule: The live region container must exist in the DOM before you inject content into it. Adding both the container and the content simultaneously often fails to trigger announcements.

---

aria-hidden — Rules and Common Mistakes

aria-hidden="true" removes an element and all its descendants from the accessibility tree.

Correct Uses

<!-- Decorative icon inside a labeled button -->
<button type="button" aria-label="Close">
  <svg aria-hidden="true" focusable="false">...</svg>
</button>

<!-- Decorative image -->
<img src="hero-bg.jpg" alt="" aria-hidden="true">

<!-- Modal: hide background content -->
<main aria-hidden="true" inert>...</main>

Forbidden Uses

<!-- ❌ CRITICAL: aria-hidden on a focusable element -->
<button aria-hidden="true">Submit</button>
<!-- Screen reader can't see it; keyboard user can still Tab to it — disorienting -->

<!-- ❌ CRITICAL: aria-hidden ancestor contains focusable descendants -->
<div aria-hidden="true">
  <button>Click me</button>  <!-- Keyboard reaches it; screen reader can't -->
</div>

<!-- ❌ Never hide content that provides information without a visible alternative -->
<nav aria-hidden="true">
  <a href="/">Home</a>  <!-- Navigation is now invisible to AT users -->
</nav>

Rule: If aria-hidden="true" is on an element, that element and all its children must be non-focusable. Use inert attribute as the modern alternative (removes focus AND hides from AT simultaneously).

---

React ARIA Patterns

Boolean vs. String ARIA States

// ❌ WRONG: String "true"/"false" — technically works, but brittle
<button aria-expanded="true">Toggle</button>

// ✅ CORRECT: JSX boolean expression — stays in sync with state
const [isOpen, setIsOpen] = useState(false);
<button aria-expanded={isOpen}>Toggle</button>

Radix UI asChild — Preserve ARIA Plumbing

// ✅ CORRECT: Radix passes all ARIA props through asChild
<Dialog.Trigger asChild>
  <Button variant="outline">  {/* Button must spread props + forwardRef */}
    Open
  </Button>
</Dialog.Trigger>

// ❌ WRONG: Custom component that swallows props
const Button = ({ children, onClick }) => (
  <button onClick={onClick}>{children}</button>
  // Missing: {...props} spread — loses aria-haspopup, aria-expanded, etc.
);

---

Roving Tabindex Pattern — Implementation

Used in: tablist, toolbar, menu, listbox, tree, radiogroup, grid

const [focusedIndex, setFocusedIndex] = useState(0);
const itemRefs = useRef([]);

function handleKeyDown(e, index) {
  const count = items.length;
  if (e.key === 'ArrowRight' || e.key === 'ArrowDown') {
    const next = (index + 1) % count;
    setFocusedIndex(next);
    itemRefs.current[next]?.focus();
  }
  if (e.key === 'ArrowLeft' || e.key === 'ArrowUp') {
    const prev = (index - 1 + count) % count;
    setFocusedIndex(prev);
    itemRefs.current[prev]?.focus();
  }
  if (e.key === 'Home') { setFocusedIndex(0); itemRefs.current[0]?.focus(); }
  if (e.key === 'End')  { const last = count-1; setFocusedIndex(last); itemRefs.current[last]?.focus(); }
}

return (
  <div role="tablist">
    {items.map((item, i) => (
      <button
        key={item.id}
        role="tab"
        tabIndex={i === focusedIndex ? 0 : -1}
        aria-selected={i === focusedIndex}
        ref={el => itemRefs.current[i] = el}
        onKeyDown={e => handleKeyDown(e, i)}
        onClick={() => setFocusedIndex(i)}
      >
        {item.label}
      </button>
    ))}
  </div>
);