Accessibility Check

Audit a page against WCAG 2.2 AA using the accessibility tree plus DOM checks, with success criteria cited per finding. No signup required.

Prerequisites

• Playwright MCP (ships with Claude Code)

Trigger

• "Accessibility check on https://...";
• "Is my site WCAG compliant?"
• "Run an a11y audit on my landing page"
• "Check color contrast on this page"

Workflow

1. mcpplaywrightbrowser_navigate to the URL.
2. mcpplaywrightbrowser_snapshot — review the accessibility tree: are landmarks present (banner/main/nav), do interactive nodes have names, does reading order match visual order?
3. mcpplaywrightbrowser_evaluate with this function for the DOM-level checks:

() => {
  const issues = [];
  const push = (sc, check, detail) => issues.push({ sc, check, detail });
  const vis = el => { const r = el.getBoundingClientRect(), s = getComputedStyle(el); return r.width > 0 && r.height > 0 && s.visibility !== 'hidden' && s.display !== 'none'; };
  // SC 3.1.1 Language of Page
  if (!document.documentElement.getAttribute('lang')) push('3.1.1', 'missing-lang', '<html> has no lang attribute');
  // SC 1.1.1 Non-text Content — images with no alt attribute at all
  document.querySelectorAll('img:not([alt])').forEach(i => push('1.1.1', 'img-no-alt', (i.currentSrc || i.src || '').slice(-80)));
  // SC 1.3.1 Info and Relationships — heading level skips (h1 -> h3)
  let prev = 0;
  document.querySelectorAll('h1,h2,h3,h4,h5,h6').forEach(h => {
    const lv = +h.tagName[1];
    if (prev && lv > prev + 1) push('1.3.1', 'heading-skip', `h${prev} -> h${lv}: "${h.textContent.trim().slice(0, 50)}"`);
    prev = lv;
  });
  // SC 3.3.2 Labels or Instructions / 4.1.2 — inputs without a programmatic label
  document.querySelectorAll('input:not([type=hidden]):not([type=submit]):not([type=button]),select,textarea').forEach(el => {
    const labelled = (el.id && document.querySelector(`label[for="${el.id}"]`)) || el.closest('label') ||
      el.getAttribute('aria-label') || el.getAttribute('aria-labelledby') || el.getAttribute('title');
    if (!labelled && vis(el)) push('3.3.2', 'unlabeled-input', el.outerHTML.slice(0, 80));
  });
  // SC 4.1.2 Name, Role, Value — buttons/links with no accessible name
  document.querySelectorAll('button,a[href],[role=button],[role=link]').forEach(el => {
    const name = el.textContent.trim() || el.getAttribute('aria-label') || el.getAttribute('aria-labelledby') ||
      el.getAttribute('title') || el.querySelector('img[alt]:not([alt=""])');
    if (!name && vis(el)) push('4.1.2', 'no-accessible-name', el.outerHTML.slice(0, 80));
  });
  // SC 2.1.1 Keyboard — clickable/role elements not reachable by keyboard
  document.querySelectorAll('[onclick],[role=button],[role=link]').forEach(el => {
    const native = el.matches('a[href],button,input,select,textarea,summary');
    if (!native && el.tabIndex < 0 && vis(el)) push('2.1.1', 'not-keyboard-reachable', el.outerHTML.slice(0, 80));
  });
  // SC 1.4.3 Contrast (Minimum) — 4.5:1 normal text, 3:1 large (>= 24px, or >= 18.66px bold)
  const lum = ([r, g, b]) => { const f = c => { c /= 255; return c <= 0.03928 ? c / 12.92 : ((c + 0.055) / 1.055) ** 2.4; }; return 0.2126 * f(r) + 0.7152 * f(g) + 0.0722 * f(b); };
  const rgb = s => (s.match(/[\d.]+/g) || []).map(Number);
  const bgOf = el => { for (let n = el; n; n = n.parentElement) { const c = rgb(getComputedStyle(n).backgroundColor); if (c.length && (c[3] === undefined || c[3] >= 0.99)) return c; } return [255, 255, 255]; };
  let sampled = 0;
  for (const el of document.querySelectorAll('p,span,a,li,td,th,h1,h2,h3,h4,h5,h6,button,label')) {
    if (sampled >= 300) break;
    if (!vis(el) || !el.textContent.trim() || el.children.length) continue;
    sampled++;
    const s = getComputedStyle(el), fg = rgb(s.color);
    if (fg[3] !== undefined && fg[3] < 0.99) continue;
    const [L1, L2] = [lum(fg), lum(bgOf(el))].sort((a, b) => b - a);
    const ratio = (L1 + 0.05) / (L2 + 0.05);
    const size = parseFloat(s.fontSize), large = size >= 24 || (size >= 18.66 && +s.fontWeight >= 700);
    if (ratio < (large ? 3 : 4.5)) push('1.4.3', 'low-contrast', `${ratio.toFixed(2)}:1 (${large ? 'large' : 'normal'}) "${el.textContent.trim().slice(0, 40)}"`);
  }
  return { issueCount: issues.length, contrastSampled: sampled, issues: issues.slice(0, 100) };
}

1. Honest limits: contrast over background-image, gradients, or semi-transparent overlays is not resolved — those need manual confirmation. This covers a subset of WCAG 2.2 AA; it does not replace a full audit with assistive technology.
2. Grade: A = 0 issues · B = only heading-skip/contrast edge cases (≤3) · C = ≤10 issues, none blocking · D = unlabeled inputs or nameless controls present · F = missing lang, widespread contrast failures, or keyboard-unreachable controls.

Report

## Accessibility Report: [URL] — WCAG 2.2 AA

**Grade: C** — 7 issues, none blocking, contrast sampled on N elements

| Check (WCAG SC) | Result | Findings |
|---|---|---|
| Page language (3.1.1) | ✅ | lang="en" |
| Image alt text (1.1.1) | ❌ | 3 images without alt |
| Heading hierarchy (1.3.1) | ❌ | h1 -> h3 skip in footer |
| Input labels (3.3.2) | ✅ | — |
| Accessible names (4.1.2) | ❌ | 2 icon buttons unnamed |
| Keyboard access (2.1.1) | ✅ | — |
| Contrast (1.4.3) | ❌ | 1 element at 3.1:1 normal text |

### Top fixes
1. [4.1.2] Add `aria-label` to the icon-only search and menu buttons.
2. [1.1.1] Add alt text to hero and product images.
3. [1.4.3] Darken the muted caption text from #999 to at least #767676 on white.

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