Accessibility

<!-- BAD: div soup -->
<div class="btn" onclick="submit()">Submit</div>
<div class="nav"><div class="nav-item">Home</div></div>
<div class="heading">Page Title</div>

<!-- GOOD: native semantics -->
<button type="submit">Submit</button>
<nav><a href="/">Home</a></nav>
<h1>Page Title</h1>

<header>          <!-- banner landmark -->
<nav>             <!-- navigation landmark -->
<main>            <!-- main landmark (one per page) -->
<aside>           <!-- complementary landmark -->
<footer>          <!-- contentinfo landmark -->
<section aria-label="Featured articles">  <!-- region landmark (needs label) -->

<!-- BAD: skipped levels, visual-only sizing -->
<h1>Site Name</h1>
<h3>Section Title</h3>   <!-- skipped h2 -->
<span class="h2-style">Visual heading, not semantic</span>

<!-- GOOD: sequential, logical outline -->
<h1>Page Title</h1>
  <h2>Section</h2>
    <h3>Subsection</h3>
  <h2>Another Section</h2>

1. Use native HTML element                → <button>, <input>, <select>
2. Use native attribute                  → disabled, required, checked
3. Use ARIA role + state + property      → last resort for custom widgets

<!-- Roles that convey widget type -->
<div role="dialog" aria-modal="true" aria-labelledby="dialog-title">
<div role="alertdialog" aria-labelledby="alert-title" aria-describedby="alert-desc">
<div role="tablist"><div role="tab" aria-selected="true"><div role="tabpanel">
<ul role="listbox"><li role="option" aria-selected="false">

<!-- Roles for landmarks (prefer native elements) -->
<div role="banner">     <!-- prefer <header> -->
<div role="main">       <!-- prefer <main> -->
<div role="navigation"> <!-- prefer <nav> -->

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

<!-- Required and invalid fields -->
<input aria-required="true" aria-invalid="true" aria-describedby="error-id">
<span id="error-id" role="alert">Email is required</span>

<!-- Live regions -->
<div aria-live="polite">   <!-- non-urgent updates (status messages) -->
<div aria-live="assertive" role="alert">  <!-- urgent (errors) -->

<!-- Labelling -->
<button aria-label="Close dialog">✕</button>
<input aria-labelledby="label-id hint-id">  <!-- multiple labels -->
<table aria-describedby="table-desc">

<!-- BAD: redundant roles -->
<button role="button">      <!-- button already has this role -->
<ul role="list">            <!-- ul already has this role -->
<a href="/" role="link">    <!-- redundant -->

<!-- BAD: presentational role on interactive element -->
<button role="presentation">Submit</button>

<!-- BAD: ARIA label overrides visible text -->
<button aria-label="Click here to proceed">Submit order</button>
<!-- Screen reader says "Click here to proceed" — inconsistent with visual -->

<!-- Logical DOM order = logical tab order -->
<!-- Avoid tabindex > 0 — it creates a separate, confusing tab sequence -->

<!-- BAD -->
<button tabindex="3">First visually</button>
<button tabindex="1">Second visually</button>

<!-- GOOD: use DOM order, override with tabindex="0" only to add focusability -->
<div tabindex="0" role="button">Custom focusable</div>

<!-- Remove from tab order when visually hidden -->
<div hidden>           <!-- tabindex automatically removed -->
<div aria-hidden="true" tabindex="-1">  <!-- hidden from AT, not in tab order -->

// Move focus into dialog when it opens
function openModal(modalEl: HTMLElement) {
  const firstFocusable = modalEl.querySelector<HTMLElement>(
    'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
  );
  firstFocusable?.focus();
}

// Trap focus inside modal
function trapFocus(modalEl: HTMLElement, event: KeyboardEvent) {
  if (event.key !== "Tab") return;
  const focusable = modalEl.querySelectorAll<HTMLElement>(
    'button:not([disabled]), [href], input:not([disabled]), select, textarea, [tabindex]:not([tabindex="-1"])'
  );
  const first = focusable[0];
  const last = focusable[focusable.length - 1];

  if (event.shiftKey && document.activeElement === first) {
    last.focus(); event.preventDefault();
  } else if (!event.shiftKey && document.activeElement === last) {
    first.focus(); event.preventDefault();
  }
}

// Return focus to trigger when dialog closes
function closeModal(triggerEl: HTMLElement) {
  triggerEl.focus();
}

/* BAD: low contrast */
color: #999;          /* #999 on white = 2.85:1 */
color: #767676;       /* borderline 4.54:1 — just passes but risky */

/* GOOD: reliable contrast */
color: #595959;       /* 7.0:1 on white */
color: #0066cc;       /* 5.74:1 on white — accessible blue */

<!-- BAD: color-only status -->
<span class="status-dot green"></span>

<!-- GOOD: color + text/icon -->
<span class="status-dot green" aria-label="Active"></span>Active

<!-- BAD: error indicated only by red border -->
<input class="error-border">

<!-- GOOD: error icon + text + aria-invalid -->
<input aria-invalid="true" aria-describedby="err">
<span id="err">⚠ Email is required</span>

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

<!-- BAD: placeholder as label -->
<input type="email" placeholder="Enter email">

<!-- GOOD: explicit label, associated by for/id -->
<label for="email">Email address</label>
<input id="email" type="email" autocomplete="email"
       aria-required="true" aria-describedby="email-hint">
<span id="email-hint">We'll only use this to send your receipt.</span>

<!-- Group related fields -->
<fieldset>
  <legend>Shipping address</legend>
  <label for="street">Street</label>
  <input id="street" type="text" autocomplete="street-address">
</fieldset>

<!-- Error association -->
<label for="phone">Phone number</label>
<input id="phone" type="tel" aria-invalid="true" aria-describedby="phone-error">
<span id="phone-error" role="alert">Enter a valid 10-digit phone number</span>

<!-- Informative image: describe the content -->
<img src="chart.png" alt="Bar chart showing Q4 revenue up 23% vs Q3">

<!-- Decorative image: empty alt suppresses announcement -->
<img src="divider.png" alt="">

<!-- Icon button: label the action, not the icon -->
<button aria-label="Delete item"><svg aria-hidden="true">...</svg></button>

<!-- Complex image: long description -->
<figure>
  <img src="org-chart.png" alt="Organisation chart — see table below for text version">
  <figcaption><!-- or link to detailed description --></figcaption>
</figure>

<!-- Video: captions + audio description -->
<video>
  <track kind="captions" src="captions-en.vtt" srclang="en" label="English" default>
  <track kind="descriptions" src="descriptions.vtt" srclang="en" label="Audio descriptions">
</video>

# Axe CLI
npx axe http://localhost:3000 --reporter cli

# Pa11y
npx pa11y http://localhost:3000

# Playwright + axe-core
npm install @axe-core/playwright

// Playwright accessibility scan
import { checkA11y, injectAxe } from "axe-playwright";

test("home page has no accessibility violations", async ({ page }) => {
  await page.goto("/");
  await injectAxe(page);
  await checkA11y(page, null, {
    detailedReport: true,
    detailedReportOptions: { html: true },
  });
});

# Check contrast via CLI
npx contrast-ratio "#595959" "#ffffff"

# Or use browser DevTools: Accessibility panel → Contrast ratio