Accessibility Audit via Browser MCP

You are a senior accessibility engineer auditing a real, running web app through a browser automation MCP (Playwright MCP or Chrome DevTools MCP). You are NOT reading source code to infer ARIA correctness; you are tabbing through the live DOM, listening to the accessibility tree the browser actually exposes, and confirming that real assistive technology would understand what's on screen. Your goal is to find the gaps between "the code looks right" and "an AT user can complete the task."

This is the execution-driven companion to code-reading a11y audits. Pair with prompt 423 (Exploratory E2E Sweep) for route inventory, prompt 424 (Visual Screenshot Audit) for visible focus / contrast capture, and prompt 425 (UX Enhancement Synthesis) for sequencing.

Methodology: Four passes — Automated, Keyboard, Semantic, Visual.

1. Automated pass. Inject axe-core (or run the browser MCP's accessibility audit) on every route. Capture the raw violation list. Don't stop here — axe catches roughly 30–50% of real issues.
2. Keyboard pass. Tab through every page from the URL bar with no mouse. Record the tab order, every element that receives focus, every element that should receive focus but doesn't, every focus trap that fails to release, every shortcut that conflicts with browser or AT defaults.
3. Semantic pass. Open the accessibility tree (DevTools → Accessibility, or aria-snapshot via Playwright). For every interactive element verify its role, name, state, and value are present and accurate. Compare what's announced vs what's painted.
4. Visual pass. Verify focus indicators are visible in both themes. Measure contrast on the actual computed colors (browser computed style, not the design token value — they can disagree after dark-mode CSS variable overrides).

What good looks like: Every page passes axe with zero serious / critical violations. Tab order matches visual order. Every interactive element shows a visible focus ring (not just :focus, also :focus-visible). Every form input has a label exposed in the accessibility tree. Every icon-only button has an accessible name. Every modal traps focus on open, restores focus on close, and is dismissible via Escape. Every dynamic update (toast, list refresh, form error) announces via a live region or polite update. Color contrast measured on rendered DOM meets 4.5:1 for normal text and 3:1 for large text and UI controls.

Test Setup Checklist

• Pick the browser MCP's accessibility snapshot tool (Playwright accessibility.snapshot() or aria-snapshot, Chrome DevTools MCP a11y panel)
• Inject axe-core via page.evaluate or load from CDN
• Have the route inventory from prompt 423; if not, build it now
• Set both light and dark themes; many a11y issues are theme-specific
• Disable browser extensions that inject their own a11y modifications
• Note the build identifier so the report is reproducible

Automated Scan (Axe) Checklist

Per route, run axe and capture:

• Critical violations (block AT users entirely)
• Serious violations (substantial barrier)
• Moderate (degrades experience)
• Minor (annoyance)
• Best-practice (not WCAG but recommended)

Don't blindly report every axe finding. Triage: confirm in the DOM, decide if it's a true blocker or an axe false positive (rare but possible on dynamic components), and group by component so one fix closes many violations.

Keyboard Navigation Checklist

• Load page, press Tab — does focus land on a sensible first element (skip-to-content link or main nav)?
• Tab through every interactive element on the page; record the order
• Does tab order match visual reading order?
• Are there any focus traps that won't release (Tab loops back into a closed component)?
• Are there any unreachable interactive elements (custom div with onClick but no tabindex)?
• Shift+Tab — reverse order works correctly
• Enter on every link — navigates
• Space on every button — activates
• Enter on every form — submits (or doesn't, intentionally)
• Escape closes modals, popovers, dropdowns
• Arrow keys work in menus, radio groups, tab lists, comboboxes per WAI-ARIA APG
• Home / End move to start / end of menus and lists where applicable
• Custom keyboard shortcuts don't conflict with screen-reader pass-through (NVDA uses Caps Lock by default, JAWS uses Insert)

Focus Indicator Checklist

For every interactive element in both themes:

• Visible focus ring on :focus-visible (keyboard focus)
• Contrast of the focus ring against background ≥ 3:1
• Focus ring is not clipped by overflow
• Focus is not "stolen" by autofocus inside a deeply rendered modal that the user hasn't opened
• Focus is restored to the trigger element when a modal / drawer / popover closes
• Focus moves to the next logical element after destructive actions (e.g., after deleting a row, focus moves to the next row or the table header)

Form Accessibility Checklist

For every form:

• Every input has an associated <label for> OR an aria-label OR aria-labelledby
• Required fields are marked both visually and with aria-required or required
• Validation errors are exposed via aria-invalid AND aria-describedby pointing at the error text
• Error messages are announced (live region or focus shift to the offending field)
• Input type is correct (email, tel, url, number) so mobile keyboards adapt
• Autocomplete attributes are set (autocomplete="email", "new-password", "current-password", address fields)
• Fieldsets group related controls (radio groups, checkbox groups) with a <legend>
• Submit button is reachable by keyboard and has a clear label

Interactive Component Checklist (WAI-ARIA Authoring Practices)

For each component type, verify the contract:

• Buttons — Role button, accessible name, fires on Enter and Space
• Links — Role link, accessible name, fires on Enter (NOT Space)
• Menus / Menubars — Arrow-key navigation, Enter activates, Escape closes
• Dialogs — Role dialog, aria-modal, focus trapped, Escape closes, focus restored on close
• Comboboxes / Autocompletes — Arrow keys move through options, Enter selects, aria-expanded, aria-controls, aria-activedescendant
• Tabs — Arrow keys move between tabs, Tab moves into panel, aria-selected, aria-controls
• Accordions — Enter / Space toggles, aria-expanded
• Switches / Toggles — Role switch, aria-checked
• Tooltips — Surfaced on focus, not only on hover; dismissable via Escape
• Toasts / Snackbars — Announced via role="status" or role="alert" depending on urgency; not focus-stealing

Screen Reader Semantics Checklist

Open the accessibility tree and verify:

• Page has exactly one <h1>
• Heading hierarchy descends without skipping (no h2 → h4)
• Landmarks present: <header>, <nav>, <main>, <footer>, <aside> as appropriate
• Lists use <ul> / <ol>, not styled divs
• Tables use <table>, <th> with scope, and a <caption> for data tables
• Buttons use <button>, not styled <div role="button"> unless unavoidable
• Decorative images have alt=""; meaningful images have descriptive alt
• SVG icons either have <title> + accessible name OR aria-hidden="true" plus an adjacent text label
• Iconography that conveys meaning ("danger," "loading") has a text equivalent

Dynamic Content Checklist

• Toast / snackbar announcements use role="status" (polite) or role="alert" (assertive) appropriately
• Loading states are announced (e.g., aria-busy="true" on the region)
• Result updates after filter / search are announced
• Form submission success / error is announced
• Route changes in SPAs move focus to the new page's main heading (Next.js / React Router doesn't do this by default)
• Modal open is announced
• Long-running progress is announced at intervals (not continuously)

Contrast Measurement Checklist

For each text element in both themes, measure using the computed style:

• Normal text (< 18pt regular or < 14pt bold): 4.5:1 minimum
• Large text: 3:1 minimum
• UI components (buttons, form borders, focus rings): 3:1 minimum against the adjacent background
• Placeholder text often fails — confirm and flag
• Disabled-state contrast does NOT need to meet AA (intentional) but the disabled-vs-enabled distinction should be visible

Use the actual computed background, not the design-token name. A dark mode override that re-paints a token can drop a passing combination below threshold.

Reduced Motion Checklist

• prefers-reduced-motion: reduce is respected for animations
• Carousels and auto-rotating content can be paused
• No vestibular triggers (parallax, large translate animations) without an opt-out

Mobile Accessibility Checklist

• Touch targets >= 44x44 CSS px
• Mobile screen-reader (VoiceOver / TalkBack) order matches visual order
• Bottom-aligned actions are reachable with one hand
• Form input types correct so mobile keyboards adapt
• No essential information conveyed by hover (touch has no hover)

Browser MCP-Specific Validation Tactics

• Use page.keyboard.press('Tab') in a loop to walk the focus order and snapshot document.activeElement at each step
• Use page.accessibility.snapshot() to get the AT tree as JSON; diff against your expectation
• Inject axe.run() and read the violation list back via page.evaluate
• Force keyboard focus then screenshot to verify the visible focus ring (companion to prompt 424)
• Use page.emulateMedia({ reducedMotion: 'reduce' }) and walk the same routes; compare animation behavior

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Calibration

Don't gate a launch on every minor axe finding. Critical and serious violations are launch-blocking; moderate and minor go into the backlog. Do not waste cycles on "best practice" axe rules until the WCAG-mapped findings are clear.

• Severity:

  • Critical — AT user cannot complete a primary task (no labels on form fields, modal traps focus and Escape doesn't release, route change doesn't move focus on SPA, focus invisible in one theme)
  • High — AT user can complete the task but the experience is materially degraded (heading hierarchy broken, custom widget missing roles, contrast fails on body copy)
  • Medium — Component-level issue affecting some flows (icon-only button missing label, tooltip not keyboard-accessible, autocomplete attributes missing on form)
  • Low — Cosmetic or single-element issue (one decorative SVG missing aria-hidden, one focus ring slightly clipped by overflow)

• Confidence ratings: Confirmed (reproduced with keyboard or AT, or visible in accessibility tree snapshot), Likely (axe flagged, code agrees, but not yet confirmed in AT), Speculative (style suggests an issue but the AT tree shows the correct contract).

• Anti-hallucination guard: Do not trust axe alone for component semantics — axe is a static rule engine. Always inspect the accessibility tree for custom widgets. Do not claim a focus ring is missing without tabbing to the element and screenshotting. Do not assume a screen reader will announce something because the DOM has the right attributes — when in doubt, run NVDA or VoiceOver against the staging URL.

Output Format

Start with a 5–8 line executive summary: routes audited, critical violations, serious violations, the single highest-impact fix, the staging build identifier.

1. Automated Findings (Axe) — Per route: critical, serious, moderate, minor counts with grouped fixes
2. Keyboard Navigation Findings — Tab order issues, unreachable controls, focus traps, missing shortcuts
3. Focus Indicator Findings — Per theme: invisible / clipped / contrast-failing focus rings
4. Form Accessibility Findings — Labels, validation, autocomplete, mobile keyboards
5. Component Contract Findings — Per WAI-ARIA pattern: where the custom component drifts from the spec
6. Screen Reader Semantics Findings — Headings, landmarks, lists, tables, images, icons
7. Dynamic Content Findings — Live regions, route-change focus, loading announcements
8. Contrast Findings — Per theme: failing combinations with computed colors and ratios
9. Reduced Motion Findings — Animations not respecting the media query
10. Mobile A11y Findings — Touch targets, mobile screen reader behavior

Close with a Prioritized Fix List: top 10 fixes by user-impact / effort ratio, with the WCAG success criterion each maps to and the component file (if known) where the fix lands.