Google Lighthouse

An open-source, automated tool built into Chrome DevTools for auditing web page quality. Lighthouse provides comprehensive reports on accessibility, performance, SEO, and best practices.

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Tool Overview

Attribute Details
Developer Google Chrome Team
Tool Type Automated web quality auditing tool
Platforms Chrome DevTools, CLI, Node.js, PageSpeed Insights
Pricing Completely free and open source
Accessibility Engine Powered by axe-core
Website developer.chrome.com/docs/lighthouse
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What is Lighthouse?

Google Lighthouse is a comprehensive web page auditing tool that analyzes websites across multiple dimensions: performance, accessibility, progressive web app compliance, SEO, and general best practices. Originally launched in 2016, it has become one of the most widely used tools for assessing website quality.

Lighthouse runs a series of automated tests against a page and generates a report with scores from 0-100 in each category. For accessibility, Lighthouse uses the axe-core testing engine to check for WCAG violations and other accessibility issues.

Because Lighthouse is built into Chrome DevTools and available through Google's PageSpeed Insights, it's easily accessible to developers, designers, and stakeholders alike without requiring any installation.

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Key Features & Capabilities

Audit Categories

  • Accessibility: WCAG compliance checks powered by axe-core
  • Performance: Core Web Vitals, loading speed, interactivity metrics
  • Best Practices: Security, modern web standards, browser compatibility
  • SEO: Search engine optimization fundamentals
  • PWA: Progressive Web App requirements

Accessibility Checks

Lighthouse tests for common accessibility issues including:

  • Missing alt text on images
  • Insufficient color contrast ratios
  • Missing form labels and ARIA attributes
  • Incorrect heading hierarchy
  • Missing document language
  • Keyboard accessibility issues
  • ARIA attribute validity
  • Focus management problems

Report Features

  • Numeric scores (0-100) for each category
  • Detailed issue descriptions with impact level
  • Links to learn more about each issue
  • Opportunities for improvement with estimated impact
  • Passed audits confirmation
  • Export to JSON, HTML, or PDF
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How to Use Lighthouse

Chrome DevTools (Easiest)

  1. Open Chrome and navigate to the page you want to test
  2. Open DevTools (F12 or Right-click > Inspect)
  3. Click on the "Lighthouse" tab
  4. Select the categories you want to audit (check "Accessibility")
  5. Choose device type (Mobile or Desktop)
  6. Click "Analyze page load"
  7. Review the generated report

PageSpeed Insights

  1. Go to pagespeed.web.dev
  2. Enter the URL you want to test
  3. Click "Analyze"
  4. Review results for both mobile and desktop

Command Line Interface

# Install Lighthouse CLI
npm install -g lighthouse

# Run an audit
lighthouse https://example.com --output html --output-path ./report.html

# Run only accessibility audit
lighthouse https://example.com --only-categories=accessibility

Node.js Integration

const lighthouse = require('lighthouse');
const chromeLauncher = require('chrome-launcher');

async function runLighthouse(url) {
  const chrome = await chromeLauncher.launch();
  const options = {
    port: chrome.port,
    onlyCategories: ['accessibility']
  };
  const result = await lighthouse(url, options);
  console.log(result.lhr.categories.accessibility.score);
  await chrome.kill();
}
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What Lighthouse Tests For

WCAG Category Issues Detected
Perceivable Image alt text, color contrast, video captions requirements
Operable Keyboard navigation, skip links, focus indicators
Understandable Page language, form labels, error identification
Robust Valid ARIA usage, duplicate IDs, parsing errors

Understanding Scores

90-100: Good - Minor issues only
50-89: Needs Improvement - Several issues to address
0-49: Poor - Significant accessibility barriers present

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Quick Facts

Best For: Quick accessibility audits and ongoing monitoring

Skill Level: Beginner-friendly

Time to Learn: 5-10 minutes

Output: Detailed HTML/JSON reports with scores

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Pricing

100% Free

  • Built into Chrome (no installation)
  • PageSpeed Insights is free
  • CLI tool is free
  • Open source on GitHub
  • No usage limits
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Pros & Cons

Advantages

  • Free and built into Chrome
  • Easy to use, no setup required
  • Comprehensive multi-category audits
  • Uses proven axe-core engine
  • CI/CD integration options
  • Great for stakeholder reports

Limitations

  • Cannot detect all accessibility issues
  • Only tests single page states
  • Scores can vary between runs
  • Doesn't test authenticated pages easily
  • No guided manual testing
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Best Practices for Using Lighthouse

Getting Accurate Results

  1. Use Incognito Mode: Prevents extensions from affecting results
  2. Run Multiple Times: Scores can vary; average several runs
  3. Test on Staging: Production CDNs and caching can affect results
  4. Test Key Pages: Don't just test the homepage

Integrating into Workflow

  1. Set Baselines: Establish minimum acceptable scores
  2. Automate with CI: Fail builds that drop below thresholds
  3. Track Over Time: Monitor score changes across releases
  4. Combine with Manual Testing: Lighthouse is just the first step

Important Limitation

A score of 100 does not mean your site is fully accessible. Lighthouse can only detect about 30-40% of accessibility issues. Always complement automated testing with manual testing and screen reader evaluation.

Need Help Interpreting Lighthouse Results?

Our experts can help you understand and prioritize accessibility findings.

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