| name | a11y-ally |
| description | Use when running comprehensive WCAG accessibility audits with axe-core + pa11y + Lighthouse, generating context-aware remediation, or testing video accessibility. Supports 3-tier browser cascade with graceful degradation. |
| category | specialized-testing |
| priority | critical |
| tokenEstimate | 10000 |
| agents | [] |
| implementation_status | active |
| optimization_version | 7 |
| last_optimized | "2026-01-26T00:00:00.000Z" |
| dependencies | ["playwright","playwright-extra","puppeteer-extra-plugin-stealth","@axe-core/playwright","pa11y","lighthouse"] |
| quick_reference_card | true |
| tags | ["accessibility","wcag","a11y","video","captions","audiodesc","vtt","eu-compliance","context-aware","remediation","axe-core","pa11y","lighthouse","parallel","resilient","graceful-degradation","retry"] |
| trust_tier | 3 |
| validation | {"schema_path":"schemas/output.json","validator_path":"scripts/validate-config.json","eval_path":"evals/a11y-ally.yaml"} |
/a11y-ally - Comprehensive Accessibility Audit
<default_to_action>
When this skill is invoked with a URL, Claude executes ALL steps automatically without waiting for user prompts between steps.
THIS IS AN LLM-POWERED SKILL
The value of this skill is Claude's intelligence, not just running automated tools:
| Automated Tools Do | Claude (This Skill) Does |
|---|
| Flag "button has no name" | Analyze context: icon class, parent element, nearby text → generate "Add to wishlist" |
| Flag "image missing alt" | Use Vision to see the image → describe actual content |
| Flag "video has no captions" | Download video, extract frames, analyze each frame with Vision → generate real captions |
| Output generic templates | Generate context-specific, copy-paste ready fixes |
IF YOU SKIP THE LLM ANALYSIS, THIS SKILL HAS NO VALUE.
EXECUTION MODEL
CLAUDE EXECUTES ALL STEPS WITHOUT STOPPING.
Do NOT wait for user prompts between steps. Execute the full pipeline:
- Data Collection: Run multi-tool scan (axe-core, pa11y, Lighthouse) via Bash
- LLM Analysis: Read results and analyze context for each violation
- Vision Pipeline: If videos detected → download → extract frames → Read each frame → describe
- Intelligent Remediation: Generate context-specific fixes using your reasoning
- Generate Reports: Write all output files to
docs/accessibility-scans/{page-slug}/
WRONG:
Claude: "I found 5 violations. Should I analyze them?"
User: "Yes"
Claude: "I see a video. Should I run the video pipeline?"
User: "Yes"
RIGHT:
Claude: [Runs scan] → [Analyzes violations] → [Downloads video] → [Extracts frames] →
[Reads each frame with Vision] → [Generates captions] → [Writes all files]
"Audit complete. Generated 4 files in docs/accessibility-scans/example/"
STEP 1: BROWSER AUTOMATION - Content Fetching
Uses the qe-browser fleet skill as the browser engine. qe-browser wraps Vibium (WebDriver BiDi, 10MB Go binary) and provides the QE primitives we rely on. See .claude/skills/qe-browser/SKILL.md.
1.1: PRIMARY — qe-browser via Vibium CLI
vibium go "$TARGET_URL"
vibium wait load
vibium a11y-tree --json > /tmp/a11y-work/tree.json
vibium screenshot -o /tmp/a11y-work/page.png --full-page
If Vibium MCP tools are registered (mcp__vibium__*), prefer them; otherwise shell out to the vibium binary installed by aqe init.
1.2: Run axe-core + WCAG assertions via qe-browser
vibium eval --stdin <<'EOF'
const s = document.createElement('script');
s.src = 'https://cdnjs.cloudflare.com/ajax/libs/axe-core/4.10.2/axe.min.js';
document.head.appendChild(s);
await new Promise(r => s.onload = r);
const results = await axe.run();
JSON.stringify({ violations: results.violations.length, issues: results.violations });
EOF
node .claude/skills/qe-browser/scripts/assert.js --checks '[
{"kind": "no_console_errors"},
{"kind": "no_failed_requests"},
{"kind": "selector_visible", "selector": "main, [role=main]"}
]'
1.3: FALLBACK — pa11y + Lighthouse (when axe alone is insufficient)
pa11y "$TARGET_URL" --reporter json > /tmp/a11y-work/pa11y.json
lighthouse "$TARGET_URL" --only-categories=accessibility --output=json --output-path=/tmp/a11y-work/lighthouse.json --chrome-flags="--headless"
Why we dropped playwright-extra + puppeteer-extra-plugin-stealth from the primary path:
- 300MB+ of Node deps vs Vibium's 10MB binary
- Redundant: Vibium uses WebDriver BiDi which is less fingerprintable than raw CDP
- Simpler: one tool instead of a cascade
1d: PARALLEL MULTI-PAGE AUDIT (Optional)
For auditing multiple URLs simultaneously, use parallel execution:
const { chromium } = require('playwright-extra');
const stealth = require('puppeteer-extra-plugin-stealth')();
const { AxeBuilder } = require('@axe-core/playwright');
chromium.use(stealth);
const MAX_CONCURRENT = 6;
async function auditUrl(browser, url) {
const context = await browser.newContext();
const page = await context.newPage();
try {
await page.goto(url, { waitUntil: 'domcontentloaded', timeout: 60000 });
await page.waitForTimeout(2000);
const axeResults = await new AxeBuilder({ page })
.withTags(['wcag2a', 'wcag2aa', 'wcag21a', 'wcag21aa', 'wcag22aa'])
.analyze();
return { url, success: true, violations: axeResults.violations };
} catch (error) {
return { url, success: false, error: error.message };
} finally {
await context.close();
}
}
async function parallelAudit(urls) {
const browser = await chromium.launch({ headless: true });
const results = [];
for (let i = 0; i < urls.length; i += MAX_CONCURRENT) {
const chunk = urls.slice(i, i + MAX_CONCURRENT);
console.log(`Auditing batch ${Math.floor(i/MAX_CONCURRENT) + 1}: ${chunk.length} URLs`);
const chunkResults = await Promise.all(
chunk.map(url => auditUrl(browser, url))
);
results.push(...chunkResults);
}
await browser.close();
return results;
}
const urls = process.argv.slice(2);
if (urls.length > 0) {
parallelAudit(urls).then(results => {
console.log(JSON.stringify(results, null, 2));
});
}
Usage for multi-page audit:
node parallel-audit.js https://example.com https://example.com/about https://example.com/contact
1e: SITE CRAWL MODE (Optional)
For comprehensive site audits, crawl and audit all pages:
async function crawlAndAudit(startUrl, maxPages = 50) {
const browser = await chromium.launch({ headless: true });
const visited = new Set();
const toVisit = [startUrl];
const results = [];
const baseUrl = new URL(startUrl).origin;
while (toVisit.length > 0 && results.length < maxPages) {
const url = toVisit.shift();
if (visited.has(url)) continue;
visited.add(url);
console.log(`[${results.length + 1}/${maxPages}] Auditing: ${url}`);
const context = await browser.newContext();
const page = await context.newPage();
try {
await page.goto(url, { waitUntil: 'domcontentloaded', timeout: 30000 });
const links = await page.evaluate((base) => {
return [...document.querySelectorAll('a[href]')]
.map(a => a.href)
.filter(href => href.startsWith(base) && !href.includes('#'))
.filter(href => !href.match(/\.(pdf|jpg|png|gif|css|js)$/i));
}, baseUrl);
links.forEach(link => {
if (!visited.has(link) && !toVisit.includes(link)) {
toVisit.push(link);
}
});
const axeResults = await new AxeBuilder({ page })
.withTags(['wcag2a', 'wcag2aa', 'wcag22aa'])
.analyze();
results.push({ url, violations: axeResults.violations });
} catch (e) {
results.push({ url, error: e.message });
}
await context.close();
}
await browser.close();
return { pagesAudited: results.length, results };
}
const [startUrl, maxPages] = process.argv.slice(2);
crawlAndAudit(startUrl, parseInt(maxPages) || 50).then(r => console.log(JSON.stringify(r, null, 2)));
STEP 2: COMPREHENSIVE WCAG SCAN (Multi-Tool, Parallel, Resilient)
IMPORTANT: This step uses THREE accessibility testing tools for maximum coverage:
- axe-core: Industry standard, excellent for ARIA and semantic issues
- pa11y: Strong on contrast, links, and HTML validation
- Lighthouse: Google's accessibility scoring with performance correlation
Combined detection rate is ~15% higher than any single tool.
2.0: RESILIENCE ARCHITECTURE (v7.0 Enhancement)
Key improvements over v6.0:
| Feature | v6.0 (Old) | v7.0 (New) |
|---|
| Tool execution | Sequential | Parallel (Promise.allSettled) |
| Timeout handling | Global 60s | Per-tool (60s/60s/90s) |
| Failure mode | All-or-nothing | Graceful degradation |
| Retry logic | None | Exponential backoff (3 retries) |
| Output style | Wait for all | Progressive (stream as ready) |
| Minimum tools | 3 required | 1 of 3 sufficient |
Coverage by tools succeeded:
- 3/3 tools: ~95% detection (optimal)
- 2/3 tools: ~85% detection (good)
- 1/3 tools: ~70% detection (acceptable)
- 0/3 tools: FAIL - retry with different strategy
2.1: Run Multi-Tool Analysis (PARALLEL + RESILIENT)
Create and run /tmp/a11y-work/multi-tool-scan.js:
const { chromium } = require('playwright-extra');
const stealth = require('puppeteer-extra-plugin-stealth')();
const { AxeBuilder } = require('@axe-core/playwright');
const pa11y = require('pa11y');
const lighthouse = require('lighthouse').default || require('lighthouse');
const { launch: launchChrome } = require('chrome-launcher');
const fs = require('fs');
chromium.use(stealth);
const TARGET_URL = process.argv[2] || 'TARGET_URL';
const OUTPUT_FILE = '/tmp/a11y-work/scan-results.json';
const SYSTEM_CHROMIUM = '/usr/bin/chromium';
function withTimeout(promise, ms, name) {
return Promise.race([
promise,
new Promise((_, reject) =>
setTimeout(() => reject(new Error(`${name} timed out after ${ms}ms`)), ms)
)
]);
}
async function withRetry(fn, name, maxRetries = 3, baseDelay = 2000) {
for (let attempt = 1; attempt <= maxRetries; attempt++) {
try {
return await fn();
} catch (error) {
const isLastAttempt = attempt === maxRetries;
console.log(`[${name}] Attempt ${attempt}/${maxRetries} failed: ${error.message}`);
if (isLastAttempt) throw error;
const delay = baseDelay * Math.pow(2, attempt - 1);
console.log(`[${name}] Retrying in ${delay}ms...`);
await new Promise(r => setTimeout(r, delay));
}
}
}
const sleep = (ms) => new Promise(r => setTimeout(r, ms));
function progressiveOutput(tool, data) {
console.log(`\n=== ${tool.toUpperCase()} COMPLETE ===`);
console.log(JSON.stringify(data, null, 2));
try {
let results = {};
if (fs.existsSync(OUTPUT_FILE)) {
results = JSON.parse(fs.readFileSync(OUTPUT_FILE, 'utf8'));
}
results[tool] = data;
results.lastUpdated = new Date().toISOString();
fs.writeFileSync(OUTPUT_FILE, JSON.stringify(results, null, 2));
} catch (e) { }
}
async function runAxeCore(url) {
console.log('[axe-core] Starting...');
const browser = await chromium.launch({
headless: true,
executablePath: SYSTEM_CHROMIUM,
args: [
'--no-sandbox',
'--disable-setuid-sandbox',
'--disable-dev-shm-usage',
'--disable-blink-features=AutomationControlled'
]
});
const context = await browser.newContext({
userAgent: 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
locale: 'en-US',
viewport: { width: 1920, height: 1080 }
});
const page = await context.newPage();
try {
await page.goto(url, { waitUntil: 'domcontentloaded', timeout: 30000 });
await sleep(2000 + Math.random() * 2000);
try {
const cookieSelectors = [
'button:has-text("Accept")', 'button:has-text("Akzeptieren")',
'button:has-text("Alle akzeptieren")', '[data-testid="cookie-accept"]',
'#onetrust-accept-btn-handler', '.cookie-consent-accept'
];
for (const selector of cookieSelectors) {
const btn = await page.$(selector);
if (btn) { await btn.click(); await sleep(500); break; }
}
} catch (e) { }
const axeResults = await new AxeBuilder({ page })
.withTags(['wcag2a', 'wcag2aa', 'wcag21a', 'wcag21aa', 'wcag22aa'])
.analyze();
const pageInfo = await page.evaluate(() => ({
title: document.title,
url: window.location.href,
lang: document.documentElement.lang,
images: {
total: document.querySelectorAll('img').length,
withAlt: document.querySelectorAll('img[alt]').length,
withoutAlt: document.querySelectorAll('img:not([alt])').length,
emptyAlt: document.querySelectorAll('img[alt=""]').length
},
headings: {
h1: Array.from(document.querySelectorAll('h1')).map(h => h.textContent.trim().slice(0,60)),
h2: document.querySelectorAll('h2').length,
h3: document.querySelectorAll('h3').length,
total: document.querySelectorAll('h1,h2,h3,h4,h5,h6').length
},
forms: {
total: document.querySelectorAll('form').length,
inputs: document.querySelectorAll('input, select, textarea').length,
buttons: document.querySelectorAll('button').length
},
links: { total: document.querySelectorAll('a').length },
aria: {
ariaLabels: document.querySelectorAll('[aria-label]').length,
roles: document.querySelectorAll('[role]').length
},
landmarks: {
main: document.querySelectorAll('main').length,
nav: document.querySelectorAll('nav').length,
header: document.querySelectorAll('header').length,
footer: document.querySelectorAll('footer').length
},
media: {
videos: document.querySelectorAll('video').length,
iframes: document.querySelectorAll('iframe').length,
videoUrls: Array.from(document.querySelectorAll('video')).map(v => {
const src = v.src || (v.querySelector('source') ? v.querySelector('source').src : '');
return {
src: src,
hasCaptions: !!v.querySelector('track[kind="captions"]')
};
})
}
}));
const violations = axeResults.violations.map(v => ({
tool: 'axe-core',
id: v.id,
impact: v.impact,
description: v.description,
help: v.help,
helpUrl: v.helpUrl,
tags: v.tags,
nodeCount: v.nodes.length,
nodes: v.nodes.slice(0, 5).map(n => ({
html: n.html.slice(0, 200),
target: n.target,
failureSummary: n.failureSummary
}))
}));
return {
success: true,
pageInfo,
violations,
passesCount: axeResults.passes.length
};
} finally {
await context.close();
await browser.close();
}
}
async function runPa11y(url) {
console.log('[pa11y] Starting...');
const results = await pa11y(url, {
standard: 'WCAG2AA',
timeout: 45000,
wait: 2000,
chromeLaunchConfig: {
executablePath: SYSTEM_CHROMIUM,
args: ['--no-sandbox', '--disable-setuid-sandbox', '--disable-dev-shm-usage']
}
});
const violations = results.issues.map(issue => ({
tool: 'pa11y',
id: issue.code,
impact: issue.type === 'error' ? 'serious' : issue.type === 'warning' ? 'moderate' : 'minor',
description: issue.message,
selector: issue.selector,
context: (issue.context || '').slice(0, 200)
}));
return { success: true, violations, total: results.issues.length };
}
async function runLighthouse(url) {
console.log('[lighthouse] Starting...');
const chrome = await launchChrome({
chromePath: SYSTEM_CHROMIUM,
chromeFlags: ['--headless', '--no-sandbox', '--disable-gpu', '--disable-dev-shm-usage']
});
try {
const result = await lighthouse(url, {
port: chrome.port,
onlyCategories: ['accessibility'],
output: 'json'
});
const lhr = result.lhr;
const score = Math.round(lhr.categories.accessibility.score * 100);
const violations = Object.values(lhr.audits)
.filter(audit => audit.score !== null && audit.score < 1)
.map(audit => ({
tool: 'lighthouse',
id: audit.id,
impact: audit.score === 0 ? 'critical' : audit.score < 0.5 ? 'serious' : 'moderate',
score: audit.score,
description: audit.title
}));
return { success: true, score, violations };
} finally {
await chrome.kill();
}
}
(async () => {
console.log('=== MULTI-TOOL ACCESSIBILITY SCAN (v7.0 PARALLEL + RESILIENT) ===');
console.log('Target:', TARGET_URL);
console.log('Strategy: Promise.allSettled with per-tool timeouts\n');
const startTime = Date.now();
const [axeResult, pa11yResult, lighthouseResult] = await Promise.allSettled([
withTimeout(
withRetry(() => runAxeCore(TARGET_URL), 'axe-core', 2, 3000),
60000, 'axe-core'
),
withTimeout(
withRetry(() => runPa11y(TARGET_URL), 'pa11y', 2, 3000),
60000, 'pa11y'
),
withTimeout(
withRetry(() => runLighthouse(TARGET_URL), 'lighthouse', 2, 3000),
90000, 'lighthouse'
)
]);
const results = {
url: TARGET_URL,
timestamp: new Date().toISOString(),
duration: `${((Date.now() - startTime) / 1000).toFixed(1)}s`,
toolsSucceeded: 0,
toolsFailed: 0,
pageInfo: null,
violations: [],
byTool: {}
};
if (axeResult.status === 'fulfilled') {
results.toolsSucceeded++;
results.pageInfo = axeResult.value.pageInfo;
results.violations.push(...axeResult.value.violations);
results.byTool['axe-core'] = {
success: true,
count: axeResult.value.violations.length,
passes: axeResult.value.passesCount
};
progressiveOutput('axe-core', axeResult.value);
} else {
results.toolsFailed++;
results.byTool['axe-core'] = { success: false, error: axeResult.reason.message };
console.log('\n[axe-core] FAILED:', axeResult.reason.message);
}
if (pa11yResult.status === 'fulfilled') {
results.toolsSucceeded++;
results.violations.push(...pa11yResult.value.violations);
results.byTool['pa11y'] = {
success: true,
count: pa11yResult.value.violations.length
};
progressiveOutput('pa11y', pa11yResult.value);
} else {
results.toolsFailed++;
results.byTool['pa11y'] = { success: false, error: pa11yResult.reason.message };
console.log('\n[pa11y] FAILED:', pa11yResult.reason.message);
}
if (lighthouseResult.status === 'fulfilled') {
results.toolsSucceeded++;
results.violations.push(...lighthouseResult.value.violations);
results.byTool['lighthouse'] = {
success: true,
score: lighthouseResult.value.score,
count: lighthouseResult.value.violations.length
};
progressiveOutput('lighthouse', lighthouseResult.value);
} else {
results.toolsFailed++;
results.byTool['lighthouse'] = { success: false, error: lighthouseResult.reason.message };
console.log('\n[lighthouse] FAILED:', lighthouseResult.reason.message);
}
const seen = new Set();
const uniqueViolations = [];
for (const v of results.violations) {
const key = (v.description || '').toLowerCase().slice(0, 50);
if (!seen.has(key)) {
seen.add(key);
uniqueViolations.push(v);
}
}
results.uniqueViolations = uniqueViolations;
results.totalUnique = uniqueViolations.length;
console.log('\n' + '='.repeat(60));
console.log('=== SCAN COMPLETE ===');
console.log('='.repeat(60));
console.log(`Tools succeeded: ${results.toolsSucceeded}/3`);
console.log(`Tools failed: ${results.toolsFailed}/3`);
console.log(`Duration: ${results.duration}`);
console.log(`Total unique violations: ${results.totalUnique}`);
if (results.toolsSucceeded === 0) {
console.log('\n⚠️ ALL TOOLS FAILED - Consider:');
console.log(' 1. Site may have strong bot protection');
console.log(' 2. Try Vibium MCP browser instead');
console.log(' 3. Check network connectivity');
} else if (results.toolsSucceeded < 3) {
console.log(`\n⚠️ Partial coverage (${results.toolsSucceeded}/3 tools) - Results still usable`);
} else {
console.log('\n✅ Full coverage achieved (3/3 tools)');
}
console.log('\n=== PAGE INFO ===');
console.log(JSON.stringify(results.pageInfo, null, 2));
console.log('\n=== VIOLATIONS BY TOOL ===');
console.log(JSON.stringify(results.byTool, null, 2));
console.log('\n=== UNIQUE VIOLATIONS ===');
console.log(JSON.stringify(results.uniqueViolations, null, 2));
fs.writeFileSync(OUTPUT_FILE, JSON.stringify(results, null, 2));
console.log(`\nResults saved to: ${OUTPUT_FILE}`);
})();
2.2: Read Scan Results
After running the scan, read the results file:
cat /tmp/a11y-work/scan-results.json
The results include:
- pageInfo: Page structure, images, headings, media
- violations: All violations from all tools (deduplicated)
- byTool: Success/failure status per tool
- toolsSucceeded: Number of tools that completed (1-3)
2.3: Graceful Degradation Decision Tree
| Tools Succeeded | Action |
|---|
| 3/3 | ✅ Full coverage - proceed with all results |
| 2/3 | ⚠️ Good coverage - note which tool failed in report |
| 1/3 | ⚠️ Basic coverage - proceed but flag limited confidence |
| 0/3 | ❌ Retry with Vibium MCP, or document failure |
2.4: MANDATORY - Check for Videos and Trigger Pipeline
After reading scan results, check pageInfo.media.videoUrls:
const results = JSON.parse(fs.readFileSync('/tmp/a11y-work/scan-results.json'));
if (results.pageInfo && results.pageInfo.media.videoUrls.length > 0) {
console.log('=== VIDEOS DETECTED - TRIGGERING VIDEO PIPELINE ===');
for (const video of results.pageInfo.media.videoUrls) {
console.log(`Video: ${video.src}`);
console.log(` Has captions: ${video.hasCaptions}`);
}
}
IF videos detected AND hasCaptions=false → STEP 7 is MANDATORY before generating reports.
STEP 3: CONTEXT-AWARE REMEDIATION (LLM-POWERED)
THIS IS WHERE CLAUDE'S INTELLIGENCE MATTERS.
Generic tools output: aria-label="[DESCRIPTION]"
You output: aria-label="Add to shopping cart" because you understand context.
3.1: Context Analysis (Use Your Reasoning)
For EACH violation, Claude must:
-
READ THE HTML CONTEXT - Don't just see <button class="btn">, see:
<div class="product-card" data-product="Adidas Superstar">
<img src="superstar.jpg" alt="White sneakers">
<span class="price">$99</span>
<button class="btn add-to-cart">
<svg class="icon-cart">...</svg>
</button>
</div>
-
INFER PURPOSE from:
- Class names:
add-to-cart, wishlist, menu-toggle
- Parent context: Inside
.product-card with product data
- Icon classes:
icon-cart, icon-heart, icon-search
- Nearby text: Product name, price, "Add to bag"
- Page section: Header nav vs product grid vs checkout
-
GENERATE SPECIFIC FIX:
<button aria-label="[DESCRIPTION]">
<button aria-label="Add Adidas Superstar to cart - $99">
3.2: Confidence Scoring
Rate your confidence in each fix:
- 0.9+: Clear context (class="add-to-cart" near product name)
- 0.7-0.9: Reasonable inference (icon-cart class alone)
- <0.7: Needs human review (ambiguous context)
Include confidence in remediation.md:
### Button: `.product-card .btn` (Confidence: 0.95)
**Context:** Inside product card for "Adidas Superstar", has cart icon
**Fix:** `aria-label="Add Adidas Superstar to cart"`
3.2: Remediation Templates by Violation Type
Form Labels (WCAG 1.3.1, 3.3.2, 4.1.2)
<input type="text" name="cardNumber" placeholder="1234 5678 9012 3456">
<label for="card-number">Credit Card Number</label>
<input type="text"
id="card-number"
name="cardNumber"
placeholder="1234 5678 9012 3456"
aria-describedby="card-hint"
autocomplete="cc-number"
inputmode="numeric"
pattern="[0-9\s]{13,19}">
<span id="card-hint" class="visually-hidden">Enter 16-digit card number</span>
- Visible label aids all users
- aria-describedby provides additional context
- autocomplete enables autofill
- inputmode shows numeric keyboard on mobile
- pattern enables browser validation
Icon Buttons (WCAG 4.1.2)
<button class="menu-toggle">
<svg>...</svg>
</button>
<button class="menu-toggle"
type="button"
aria-expanded="false"
aria-controls="main-menu"
aria-label="Open navigation menu">
<svg aria-hidden="true" focusable="false">...</svg>
</button>
- aria-label describes action, not icon
- aria-expanded communicates state
- aria-controls links to menu element
- SVG hidden from assistive tech (decorative)
Color Contrast (WCAG 1.4.3)
.low-contrast { color: #767676; background: #ffffff; }
.accessible { color: #757575; background: #ffffff; } /* 4.6:1 - PASSES AA */
.high-contrast { color: #595959; background: #ffffff; } /* 7.0:1 - PASSES AAA */
| Original | AA Pass | AAA Pass | Notes |
|----------|---------|----------|-------|
| #767676 | #757575 | #595959 | Gray text |
| #0066cc | #0055b3 | #003d82 | Link blue |
| #cc0000 | #b30000 | #8b0000 | Error red |
Heading Hierarchy (WCAG 1.3.1)
<h1>Welcome</h1>
<h1>Products</h1>
<h4>Shoes</h4>
<h1>Contact</h1>
<h1>Site Name - Main Page Title</h1>
<main>
<section aria-labelledby="products-heading">
<h2 id="products-heading">Products</h2>
<h3>Shoes</h3>
<h3>Clothing</h3>
</section>
<section aria-labelledby="contact-heading">
<h2 id="contact-heading">Contact</h2>
</section>
</main>
h1: Site Name - Main Page Title
├── h2: Products
│ ├── h3: Shoes
│ └── h3: Clothing
└── h2: Contact
Skip Links (WCAG 2.4.1)
<body>
<a href="#main-content" class="skip-link">Skip to main content</a>
<a href="#main-nav" class="skip-link">Skip to navigation</a>
<header>
<nav id="main-nav" aria-label="Main navigation">...</nav>
</header>
<main id="main-content" tabindex="-1">
</main>
</body>
<style>
.skip-link {
position: absolute;
top: -100%;
left: 16px;
background: #000;
color: #fff;
padding: 12px 24px;
z-index: 10000;
text-decoration: none;
font-weight: bold;
border-radius: 0 0 4px 4px;
transition: top 0.2s;
}
.skip-link:focus {
top: 0;
outline: 3px solid #ffcc00;
outline-offset: 2px;
}
</style>
Focus Indicators (WCAG 2.4.7)
*:focus { outline: none; }
:focus-visible {
outline: 3px solid #005fcc;
outline-offset: 2px;
}
:focus:not(:focus-visible) {
outline: none;
}
a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible,
[role="button"]:focus-visible {
outline: 3px solid #005fcc;
outline-offset: 2px;
box-shadow: 0 0 0 6px rgba(0, 95, 204, 0.2);
}
.dark-bg :focus-visible {
outline-color: #ffffff;
box-shadow: 0 0 0 6px rgba(255, 255, 255, 0.3);
}
Keyboard Navigation (WCAG 2.1.1, 2.1.2)
<div class="dropdown" onclick="toggleMenu()">
Menu
</div>
<button type="button"
class="dropdown-trigger"
aria-expanded="false"
aria-controls="dropdown-menu"
onclick="toggleMenu()"
onkeydown="handleKeydown(event)">
Menu
</button>
<ul id="dropdown-menu" role="menu" hidden>
<li role="none"><a role="menuitem" href="/page1">Page 1</a></li>
<li role="none"><a role="menuitem" href="/page2">Page 2</a></li>
</ul>
<script>
function handleKeydown(event) {
switch(event.key) {
case 'Enter':
case ' ':
event.preventDefault();
toggleMenu();
break;
case 'Escape':
closeMenu();
break;
case 'ArrowDown':
event.preventDefault();
focusFirstMenuItem();
break;
}
}
</script>
Modal Focus Trap (WCAG 2.4.3)
function trapFocus(modal) {
const focusable = modal.querySelectorAll(
'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
);
const first = focusable[0];
const last = focusable[focusable.length - 1];
first?.focus();
modal.addEventListener('keydown', (e) => {
if (e.key === 'Tab') {
if (e.shiftKey && document.activeElement === first) {
e.preventDefault();
last.focus();
} else if (!e.shiftKey && document.activeElement === last) {
e.preventDefault();
first.focus();
}
}
if (e.key === 'Escape') {
closeModal();
}
});
}
function closeModal() {
modal.hidden = true;
triggerButton.focus();
}
iframe Titles (WCAG 4.1.2)
<iframe src="map.html" title="Store location map showing 5 nearby stores"></iframe>
<iframe src="video.html" title="Product demonstration video with captions"></iframe>
<iframe src="chat.html" title="Customer support chat window"></iframe>
STEP 4: USER IMPACT ANALYSIS
For each violation, calculate user impact:
4.1: Affected User Groups
| Violation Type | Affected Groups | % of Users |
|---|
| Missing alt text | Blind, low-vision | 7-10% |
| Missing form labels | Blind, screen reader users | 5-8% |
| Low color contrast | Low-vision, color blind | 8-12% |
| No keyboard access | Motor impaired, power users | 10-15% |
| Missing captions | Deaf, hard-of-hearing | 5-7% |
| Flashing content | Seizure sensitive | 0.5-1% |
| Complex language | Cognitive impairment | 10-15% |
4.2: Impact Severity Classification
BLOCKS-USAGE: User cannot complete task at all
- Missing form labels on required fields
- Keyboard traps
- Critical buttons without accessible names
IMPAIRS-USAGE: User can complete task with difficulty
- Low contrast (can read with effort)
- Missing skip links (tedious navigation)
- Incorrect heading structure (confusing)
MINOR-INCONVENIENCE: Suboptimal but functional
- Empty alt on decorative images
- Redundant ARIA
- Non-semantic HTML that works
STEP 5: ROI-BASED PRIORITIZATION
Calculate priority for each remediation:
5.1: Priority Formula
PRIORITY_SCORE = (IMPACT_WEIGHT × USERS_AFFECTED) / EFFORT_HOURS
Where:
- IMPACT_WEIGHT: Critical=10, Serious=7, Moderate=4, Minor=1
- USERS_AFFECTED: Estimated % of users impacted
- EFFORT_HOURS: Estimated fix time (0.25 to 8 hours)
5.2: Effort Estimation Guide
| Fix Type | Effort | Complexity |
|---|
| Add aria-label | 0.25h | Trivial |
| Add alt text | 0.25h | Trivial |
| Add form label | 0.5h | Simple |
| Fix color contrast | 0.5h | Simple |
| Add skip links | 1h | Simple |
| Fix heading structure | 2h | Medium |
| Add keyboard navigation | 4h | High |
| Implement focus trap | 4h | High |
| Add video captions | 8h | High |
5.3: Priority Output Format
| Rank | Violation | Impact | Users | Effort | ROI Score |
|------|-----------|--------|-------|--------|-----------|
| 1 | Form labels missing | Critical | 15% | 0.5h | 300 |
| 2 | Keyboard trap | Critical | 12% | 4h | 30 |
| 3 | Low contrast | Serious | 10% | 0.5h | 140 |
| 4 | Missing alt text | Serious | 8% | 0.25h | 224 |
STEP 6: PRODUCTION READINESS ASSESSMENT
6.1: Compliance Scoring
COMPLIANCE_SCORE = (PASSED_CRITERIA / TOTAL_CRITERIA) × 100
Production Ready if:
✓ Score ≥ 85%
✓ Zero critical violations
✓ Fewer than 3 serious violations
✓ All user journeys keyboard accessible
6.2: POUR Analysis (Perceivable, Operable, Understandable, Robust)
| Principle | Guidelines | Pass | Fail | Score |
|-----------|-----------|------|------|-------|
| Perceivable | 1.1-1.4 | 12 | 3 | 80% |
| Operable | 2.1-2.5 | 18 | 2 | 90% |
| Understandable | 3.1-3.3 | 8 | 1 | 89% |
| Robust | 4.1 | 4 | 1 | 80% |
| **TOTAL** | | **42** | **7** | **86%** |
STEP 7: VIDEO ACCESSIBILITY PIPELINE
Execute for EACH video detected on page.
7.1: Detect and Extract Video URLs (MANDATORY)
This step MUST be integrated into STEP 2 multi-tool scan.
Add this to the page.evaluate() in the multi-tool scan:
videos: {
elements: [...document.querySelectorAll('video')].map(v => ({
src: v.src || v.querySelector('source')?.src,
fullUrl: new URL(v.src || v.querySelector('source')?.src || '', window.location.href).href,
poster: v.poster,
hasCaptions: v.querySelector('track[kind="captions"]') !== null,
hasDescriptions: v.querySelector('track[kind="descriptions"]') !== null,
duration: v.duration || 'unknown',
autoplay: v.autoplay,
muted: v.muted
})),
iframes: [...document.querySelectorAll('iframe')].map(iframe => {
const src = iframe.src;
const isVideo = /youtube|vimeo|dailymotion|wistia/.test(src);
return isVideo ? { src, platform: src.match(/(youtube|vimeo|dailymotion|wistia)/)?.[1] } : null;
}).filter(Boolean)
}
MANDATORY OUTPUT: Log all video URLs found:
=== VIDEOS DETECTED ===
Video 1: https://example.com/promo.mp4 (no captions, no descriptions)
YouTube iframe: https://youtube.com/embed/xxx
7.2: Download and Extract Frames (MANDATORY for each video)
For EACH video URL found in 7.1:
mkdir -p /tmp/a11y-work/frames
curl -L -A "Mozilla/5.0" --retry 3 -o /tmp/a11y-work/video.mp4 "FULL_VIDEO_URL"
if [ -f /tmp/a11y-work/video.mp4 ] && [ -s /tmp/a11y-work/video.mp4 ]; then
echo "Video downloaded successfully"
ffmpeg -i /tmp/a11y-work/video.mp4 -vf "fps=1/3" -frames:v 10 /tmp/a11y-work/frames/frame_%02d.jpg 2>/dev/null
echo "Extracted $(ls /tmp/a11y-work/frames/*.jpg 2>/dev/null | wc -l) frames"
else
echo "VIDEO DOWNLOAD FAILED - Document this in audit-summary.md"
fi
IF VIDEO DOWNLOAD FAILS:
- Document the failure reason in audit-summary.md
- Still create video-captions violation in violations.json
- Add remediation instructions WITHOUT generated captions
- Mark video pipeline as "blocked" not "skipped"
7.3: Analyze Each Frame with Claude Vision (MANDATORY)
USE THE READ TOOL ON EACH FRAME IMAGE.
Claude Code has native vision capabilities. When you Read an image file, you SEE it.
Read /tmp/a11y-work/frames/frame_01.jpg
Read /tmp/a11y-work/frames/frame_02.jpg
Read /tmp/a11y-work/frames/frame_03.jpg
... (continue for all frames)
For EACH frame, describe:
- SCENE: Setting, environment, lighting, location
- PEOPLE: Who appears, what they're doing, expressions, clothing
- PRODUCTS: Items shown (for e-commerce: product names, colors, styles)
- TEXT: Any visible text, logos, signs, prices
- ACTION: Movement, transitions, what's happening
Example output after reading frame_01.jpg:
Frame 1 (0:00-0:03): A woman in white Adidas sneakers running on a forest trail.
Morning light filters through trees. She wears black athletic leggings and a
gray tank top. The Adidas three-stripe logo is visible on her shoes.
THIS IS THE LLM VALUE. Generic tools output "[DESCRIBE CONTENT]".
You output actual descriptions because you can SEE the image.
FALLBACK: If Read tool fails on images
Try Anthropic API directly:
const Anthropic = require('@anthropic-ai/sdk');
const fs = require('fs');
const client = new Anthropic();
const imageData = fs.readFileSync('/tmp/a11y-work/frames/frame_01.jpg').toString('base64');
const response = await client.messages.create({
model: 'claude-sonnet-4-6',
max_tokens: 500,
messages: [{
role: 'user',
content: [
{ type: 'image', source: { type: 'base64', media_type: 'image/jpeg', data: imageData } },
{ type: 'text', text: 'Describe this video frame for accessibility captions.' }
]
}]
});
LAST RESORT: Context-Based Inference (No Vision)
If vision completely unavailable, infer from:
- Video filename: "product-demo.mp4" → product demonstration
- Page context: product page → product showcase
- Surrounding text: nearby headings and descriptions
Document for each frame:
- SCENE: Setting, environment, lighting
- PEOPLE: Who, actions, expressions, clothing
- OBJECTS: Products, props, equipment
- TEXT: Visible text, logos, signs
- ACTION: Movement, transitions
- COLORS: Dominant colors, accessibility-relevant
7.4: Generate WebVTT Captions
WEBVTT
Kind: captions
Language: {detected-language}
00:00:00.000 --> 00:00:03.000
[Description from frame_01 analysis]
00:00:03.000 --> 00:00:06.000
[Description from frame_02 analysis]
7.5: Generate Audio Descriptions
WEBVTT
Kind: descriptions
Language: en
00:00:00.000 --> 00:00:03.000
SCENE: [Detailed scene for blind users]
VISUAL: [What's on screen]
TEXT: [Any readable text]
ACTION: [What's happening]
STEP 8: GENERATE COMPREHENSIVE REPORTS
8.1: Required Output Files
Save ALL files to docs/accessibility-scans/{page-slug}/:
| File | Contents |
|---|
audit-summary.md | Executive summary, scores, top issues, user impact |
remediation.md | ALL copy-paste code fixes with context |
violations.json | Machine-readable violation data |
implementation.md | Video integration guide (if videos) |
*.vtt | Caption and audio description files |
8.2: audit-summary.md Template
# Accessibility Audit Report: {Site Name}
**URL:** {url}
**Date:** {date}
**Standard:** WCAG 2.2 Level AA
## Executive Summary
| Metric | Value |
|--------|-------|
| **Compliance Score** | {score}% |
| **Production Ready** | {Yes/No} |
| **Critical Issues** | {count} |
| **Total Violations** | {count} |
| **Estimated Fix Time** | {hours}h |
## POUR Analysis
{table}
## Top 10 Issues by Priority
{priority table with ROI scores}
## User Impact Summary
{affected user groups and percentages}
## Recommendations
{prioritized action items}
8.3: remediation.md Template
# Accessibility Remediation Guide: {Site Name}
## Quick Wins (Copy-Paste Ready)
### 1. Form Labels ({count} issues)
{For EACH unlabeled input: context, before/after code, rationale, confidence}
### 2. Heading Structure ({count} issues)
{Current structure visualization, fixed structure, code changes}
### 3. Color Contrast ({count} issues)
{For EACH: current colors, ratio, suggested colors, CSS fixes}
### 4. Missing Alt Text ({count} issues)
{For EACH image: context-inferred alt text suggestions}
### 5. Keyboard Navigation ({count} issues)
{For EACH: element, issue, fix code, test instructions}
### 6. Focus Indicators
{Global CSS to add}
### 7. Skip Links
{Full HTML + CSS to add}
### 8. ARIA Fixes ({count} issues)
{For EACH: context, specific aria attributes to add}
### 9. iframe Titles ({count} issues)
{For EACH: suggested title based on content}
### 10. Video Accessibility ({count} videos)
{Links to generated VTT files, implementation code}
## Testing Checklist
- [ ] Tab through entire page - all interactive elements reachable
- [ ] Screen reader announces all content correctly
- [ ] Color contrast passes (use axe DevTools)
- [ ] Works without mouse
- [ ] Works at 200% zoom
- [ ] Video captions synchronized and accurate
STEP 9: LEARNING PROTOCOL (When MCP Available)
Integrate with the learning system to improve over time.
9.1: Query Previous Patterns BEFORE Audit
Check if similar sites were audited before:
ToolSearch("select:mcp__claude-flow_alpha__memory_retrieve")
ToolSearch("select:mcp__claude-flow_alpha__hooks_intelligence_pattern_search")
mcp__claude-flow_alpha__memory_retrieve({
key: `accessibility/patterns/${domain}`,
namespace: "learning"
})
mcp__claude-flow_alpha__hooks_intelligence_pattern_search({
query: "accessibility remediation",
type: "accessibility-fix",
limit: 10
})
9.2: Store Successful Patterns AFTER Audit
Store patterns that worked for future reuse:
ToolSearch("select:mcp__claude-flow_alpha__memory_store")
ToolSearch("select:mcp__claude-flow_alpha__hooks_intelligence_pattern_store")
mcp__claude-flow_alpha__memory_store({
key: `accessibility-audit/${domain}-${Date.now()}`,
namespace: "learning",
value: {
url: auditedUrl,
timestamp: new Date().toISOString(),
violationsFound: violations.length,
criticalCount: violations.filter(v => v.impact === 'critical').length,
toolsUsed: ['axe-core', 'pa11y', 'lighthouse'],
patterns: {
commonViolations: extractTopViolationTypes(violations),
effectiveFixes: extractFixesThatWorked(remediations)
}
}
})
mcp__claude-flow_alpha__hooks_intelligence_pattern_store({
pattern: "form-label-contextual-fix",
confidence: 0.92,
type: "accessibility-remediation",
metadata: {
wcagCriteria: "1.3.1, 3.3.2, 4.1.2",
violationType: "missing-form-label",
codeTemplate: "<label for=\"{id}\">{inferredLabel}</label>",
contextSignals: ["placeholder", "nearby-text", "field-name"]
}
})
9.3: Calculate Audit Quality Score
Self-assess audit completeness (for learning feedback):
| Criteria | Points | Your Score |
|---|
| Multi-tool testing used (3 tools) | 20 | |
| All WCAG 2.2 AA criteria checked | 15 | |
| Context-aware fixes generated | 20 | |
| Confidence scores included | 10 | |
| ROI prioritization calculated | 10 | |
| Video pipeline completed (if applicable) | 15 | |
| EU compliance mapping included | 10 | |
| Total | 100 | |
Quality Levels:
- 90-100: Excellent (1.0 reward)
- 70-89: Good (0.8 reward)
- 50-69: Acceptable (0.5 reward)
- <50: Incomplete (0.0 reward - redo required)
STEP 10: SCREEN READER TESTING GUIDE
Manual testing instructions (cannot be fully automated):
10.1: NVDA (Windows - Free)
1. Download: https://www.nvaccess.org/download/
2. Install and start NVDA (Ctrl+Alt+N)
3. Navigate to audited page
Key Commands:
- H: Jump through headings
- F: Jump through form fields
- B: Jump through buttons
- T: Jump through tables
- K: Jump through links
- D: Jump through landmarks
- Tab: Move through focusable elements
Verify:
- [ ] All headings announced with correct level
- [ ] Form fields announce labels
- [ ] Buttons announce purpose
- [ ] Images announce alt text or "decorative"
- [ ] Dynamic content changes announced (aria-live)
10.2: VoiceOver (macOS - Built-in)
1. Enable: System Preferences → Accessibility → VoiceOver
2. Toggle: Cmd+F5
3. Navigate to audited page
Key Commands:
- VO+U: Open rotor (headings, links, forms, landmarks)
- VO+Space: Activate element
- VO+Right/Left: Move through content
- VO+Cmd+H: Jump to next heading
Verify:
- [ ] Rotor shows all headings hierarchically
- [ ] Forms are navigable and labels announced
- [ ] Focus order matches visual order
- [ ] All content is reachable
10.3: JAWS (Windows - Commercial)
1. Trial: https://www.freedomscientific.com/products/software/jaws/
2. Start JAWS and navigate to page
Key Commands:
- H: Next heading
- F: Next form field
- B: Next button
- T: Next table
- Ins+F6: Heading list
- Ins+F7: Link list
Verify:
- [ ] Virtual cursor mode works correctly
- [ ] Forms mode activates in forms
- [ ] All ARIA roles announced properly
10.4: Screen Reader Testing Checklist
| Test | NVDA | VoiceOver | JAWS |
|---|
| Headings hierarchy correct | [ ] | [ ] | [ ] |
| Form labels announced | [ ] | [ ] | [ ] |
| Button purposes clear | [ ] | [ ] | [ ] |
| Image alt text correct | [ ] | [ ] | [ ] |
| Links announce destination | [ ] | [ ] | [ ] |
| Landmarks navigable | [ ] | [ ] | [ ] |
| Focus order logical | [ ] | [ ] | [ ] |
| Dynamic updates announced | [ ] | [ ] | [ ] |
| No keyboard traps | [ ] | [ ] | [ ] |
| Skip links work | [ ] | [ ] | [ ] |
VALIDATION CHECKLIST
Before completing, verify ALL items:
Content Fetching (v7.0 Resilient)
Violation Analysis
Remediation Generation
Video Accessibility (MANDATORY if pageInfo.media.videos > 0)
BLOCKING: Cannot generate final reports until video pipeline attempted.
Output Files
Quality Checks
IF ANY CHECKBOX IS NO = TASK INCOMPLETE
</default_to_action>
Quick Reference Card
Usage
/a11y-ally https://example.com
v7.0 Resilience Features
| Feature | Description |
|---|
| Parallel Execution | All 3 tools run simultaneously via Promise.allSettled |
| Per-Tool Timeouts | axe: 60s, pa11y: 60s, Lighthouse: 90s |
| Retry with Backoff | 2 retries per tool with exponential backoff |
| Graceful Degradation | Continue if 1+ tools succeed |
| Progressive Output | Results stream as tools complete |
| Bot Protection | Stealth mode, random delays, cookie dismissal |
Expected Output Structure
docs/accessibility-scans/{page-slug}/
├── audit-summary.md # Executive summary with scores
├── remediation.md # ALL copy-paste code fixes
├── violations.json # Machine-readable data
├── implementation.md # Video integration (if videos)
├── video-*-captions.vtt # Captions (if videos)
└── video-*-audiodesc.vtt # Audio descriptions (if videos)
Compliance Thresholds
| Level | Min Score | Critical | Serious |
|---|
| A | 70% | 0 | ≤5 |
| AA | 85% | 0 | ≤3 |
| AAA | 95% | 0 | 0 |
Tool Coverage by Success
| Tools Succeeded | Detection Rate | Status |
|---|
| 3/3 | ~95% | ✅ Optimal |
| 2/3 | ~85% | ⚠️ Good |
| 1/3 | ~70% | ⚠️ Acceptable |
| 0/3 | — | ❌ Retry needed |
ROI Formula
ROI = (Impact × Users%) / Effort_Hours
EU Compliance Mapping
| WCAG | EN 301 549 | EU Accessibility Act |
|---|
| 1.1.1 | 9.1.1.1 | EAA-I.1 Perceivable |
| 1.4.3 | 9.1.4.3 | EAA-I.1 Perceivable |
| 2.1.1 | 9.2.1.1 | EAA-I.2 Operable |
| 2.4.7 | 9.2.4.7 | EAA-I.2 Operable |
| 3.3.2 | 9.3.3.2 | EAA-I.3 Understandable |
| 4.1.2 | 9.4.1.2 | EAA-I.4 Robust |
Critical Rules
Execution Rules (v7.0)
- ALWAYS run multi-tool scan with parallel execution (Promise.allSettled)
- ALWAYS continue if at least 1 of 3 tools succeeds (graceful degradation)
- ALWAYS document which tools failed and why in audit-summary.md
- ALWAYS use per-tool timeouts (60s/60s/90s) not global timeout
- ALWAYS retry failed tools with exponential backoff before giving up
Quality Rules
- ALWAYS analyze context before generating fixes
- ALWAYS include confidence scores with remediation
- ALWAYS calculate user impact and ROI
- ALWAYS generate copy-paste ready code
- NEVER generate placeholder/template fixes
- NEVER skip video pipeline if videos detected
- NEVER complete without remediation.md
- NEVER fail audit just because 1-2 tools failed (use graceful degradation)
Gotchas
- axe-core catches ~30% of WCAG issues — automated tools miss keyboard navigation, reading order, and cognitive issues
- Agent runs Lighthouse only and reports "accessible" — Lighthouse alone is insufficient, always run axe-core + pa11y too
- Screen reader testing requires actual screen reader interaction, not just ARIA attribute checks
- Video accessibility (captions, audio descriptions) is frequently skipped — check every
<video> element
- Color contrast tools disagree on gradients and transparency — test with actual low-vision simulation
- Playwright+Stealth may be blocked by some sites — fall back gracefully, don't skip the audit