Accessibility Patterns

Semantic HTML First

Use the correct HTML element before reaching for ARIA. Native elements provide keyboard behavior, focus management, and screen reader semantics for free:

Need	Use	Not
Button	`<button>`	`<div onClick>`
Link	`<a href>`	`<span onClick>`
Navigation	`<nav>`	`<div class="nav">`
List	`<ul>` / `<ol>`	`<div>` with divs
Heading	`<h1>`–`<h6>`	`<div class="title">`
Form field	`<input>` / `<select>` / `<textarea>`	`<div contenteditable>`
Dialog	`<dialog>`	`<div class="modal">`

The first rule of ARIA: don't use ARIA if a native HTML element does the job.

ARIA Essentials

When native elements aren't sufficient:

Roles

Add semantic meaning to generic elements:

<div role="tablist">
    <button role="tab" aria-selected="true">Tab 1</button>
    <button role="tab" aria-selected="false">Tab 2</button>
</div>
<div role="tabpanel">Content</div>

States and Properties

Communicate dynamic state to assistive technology:

<button aria-expanded="false" aria-controls="menu-content">Menu</button>
<div id="menu-content" hidden>...</div>

<input aria-invalid="true" aria-describedby="error-msg" />
<span id="error-msg">Email is required</span>

Live Regions

Announce dynamic content changes:

<div aria-live="polite" aria-atomic="true">3 results found</div>

<div role="alert">Your session is about to expire.</div>

aria-live="polite" — announces after current speech finishes.
aria-live="assertive" or role="alert" — interrupts immediately (use sparingly).

Labels

Every interactive element needs an accessible name:

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

<!-- aria-label for icon-only buttons -->
<button aria-label="Close dialog"><CloseIcon /></button>

<!-- aria-labelledby for complex labels -->
<h2 id="section-title">Billing</h2>
<form aria-labelledby="section-title">...</form>

Keyboard Navigation

Focus Order

Ensure logical tab order follows visual layout. Don't use tabindex > 0.
Use tabindex="0" to make non-interactive elements focusable when necessary.
Use tabindex="-1" to make elements programmatically focusable but not in the tab order.

Key Handlers

Implement expected keyboard patterns for custom widgets:

Widget	Keys
Button	Enter, Space to activate
Menu	Arrow keys to navigate, Enter to select, Escape to close
Tabs	Arrow keys to switch, Enter/Space to activate
Dialog	Escape to close, trap focus inside
Combobox	Arrow keys to navigate, Enter to select, Escape to close

function handleKeyDown(e: React.KeyboardEvent) {
    switch (e.key) {
        case "ArrowDown":
            e.preventDefault();
            focusNextItem();
            break;
        case "ArrowUp":
            e.preventDefault();
            focusPreviousItem();
            break;
        case "Escape":
            closeMenu();
            break;
    }
}

Focus Trapping

Modal dialogs must trap focus — Tab and Shift+Tab cycle only through elements inside the dialog:

function trapFocus(dialogRef: RefObject<HTMLDialogElement>) {
    const focusable = dialogRef.current?.querySelectorAll<HTMLElement>(
        'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])',
    );
    const first = focusable?.[0];
    const last = focusable?.[focusable.length - 1];

    function handleTab(e: KeyboardEvent) {
        if (e.key !== "Tab") return;
        if (e.shiftKey && document.activeElement === first) {
            e.preventDefault();
            last?.focus();
        } else if (!e.shiftKey && document.activeElement === last) {
            e.preventDefault();
            first?.focus();
        }
    }

    dialogRef.current?.addEventListener("keydown", handleTab);
}

Focus Restoration

When a dialog/popover closes, return focus to the element that triggered it:

const triggerRef = useRef<HTMLButtonElement>(null);

function openDialog() {
    triggerRef.current = document.activeElement as HTMLButtonElement;
    setOpen(true);
}

function closeDialog() {
    setOpen(false);
    triggerRef.current?.focus();
}

Color and Contrast

Minimum contrast ratio: 4.5:1 for normal text, 3:1 for large text (WCAG AA).
Never rely on color alone to convey meaning — add icons, text, or patterns.
Test with forced-colors mode (Windows High Contrast).

Motion

Respect the user's motion preference:

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
}

const prefersReducedMotion = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

Forms

Associate every input with a <label>.
Group related fields with <fieldset> and <legend>.
Display error messages inline, linked with aria-describedby.
Use aria-required="true" or the required attribute.
Mark invalid fields with aria-invalid="true".

Images

<!-- Informative image -->
<img src="chart.png" alt="Sales increased 25% in Q4 2025" />

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

<!-- Complex image -->
<figure>
    <img src="diagram.png" alt="System architecture overview" />
    <figcaption>Request flow from client through API gateway to microservices</figcaption>
</figure>

Testing

Keyboard-only: Tab through the entire page without a mouse.
Screen reader: Test with VoiceOver (macOS), NVDA (Windows), or TalkBack (Android).
Automated: Use axe-core, eslint-plugin-jsx-a11y, or Lighthouse accessibility audit.
Manual: Zoom to 200%, use forced colors, test with prefers-reduced-motion.
Testing Library: Use getByRole, getByLabelText — if you can't query by role, the component may have an a11y issue.

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