How to use Google Lighthouse to diagnose and fix website performance issues

Google Lighthouse is a free, open-source tool designed to diagnose and improve various aspects of a website, including performance, accessibility, SEO, and best practices. By running an audit, Lighthouse provides actionable insights that help developers and site owners enhance their websites for speed, usability, and search engine rankings. In a world where page load speed and mobile usability significantly impact user retention and rankings, Lighthouse serves as an indispensable tool for ongoing website optimization.

Using Lighthouse effectively helps:

• Improve page load speed – Identify bottlenecks causing slow performance and apply fixes.
• Boost SEO rankings – Google prioritizes fast, well-optimized websites in search results.
• Enhance user experience – Optimize accessibility and best practices for usability.
• Ensure mobile-friendliness – Assess how well your site performs on different devices.
• Monitor Core Web Vitals – Track crucial performance indicators like Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS).
• Diagnose security and compliance issues – Ensure HTTPS implementation and prevent vulnerabilities.

Step 1: Run a Google Lighthouse audit

Lighthouse audits evaluate five key areas: Performance, Accessibility, SEO, Best Practices, and Progressive Web App (PWA) compliance. Running an audit allows you to pinpoint weak spots and optimize accordingly.

How to run a Lighthouse audit:

• Via Chrome DevTools:
  1. Open Google Chrome and navigate to the webpage you want to analyze.
  2. Press F12 or Ctrl + Shift + I to open Chrome DevTools.
  3. Click on the Lighthouse tab.
  4. Choose the categories to analyze (Performance, Accessibility, SEO, Best Practices, etc.).
  5. Select the device type (Mobile or Desktop) to simulate different browsing experiences.
  6. Click Generate Report and wait for the results.
• Via PageSpeed Insights:
  1. Visit Google PageSpeed Insights.
  2. Enter your website URL and click Analyze.
  3. Review the Lighthouse-powered performance report, with detailed recommendations.
• Via CLI (Command Line Interface):
  1. Install Node.js and Lighthouse using: npm install -g lighthouse
  2. Run an audit using: lighthouse https://yourwebsite.com --view
  3. View detailed performance data in your terminal or browser.

Step 2: Analyze the performance audit results

Lighthouse assigns scores between 0 and 100 for each category, with higher scores indicating better optimization. Focus on the following key areas:

Core Web Vitals and load performance:

• Largest Contentful Paint (LCP) – Measures how quickly the main content loads.
• First Input Delay (FID) – Assesses responsiveness and interactivity.
• Cumulative Layout Shift (CLS) – Evaluates unexpected content shifts that disrupt user experience.
• Time to Interactive (TTI) – Determines when a page becomes fully interactive.
• Speed Index – Measures how quickly visible content appears during load.

Opportunities for improvement:

• Reduce render-blocking resources – Minimize CSS and JavaScript files that delay page rendering.
• Enable text compression – Use Gzip or Brotli compression to reduce file sizes.
• Optimize images – Convert images to WebP format, resize appropriately, and enable lazy loading.
• Leverage browser caching – Store assets locally to improve repeat visit performance.
• Minimize third-party scripts – Reduce dependency on external resources that slow load times.
• Improve server response time – Optimize hosting, database queries, and backend performance.

Step 3: Apply fixes to enhance website performance

Once Lighthouse identifies problem areas, apply targeted optimizations to improve site efficiency.

How to improve page speed and loading times:

• Minify CSS, JavaScript, and HTML – Reduce file sizes by eliminating unnecessary characters and whitespace.
• Defer JavaScript execution – Load JavaScript only after critical content is rendered.
• Enable lazy loading for images and videos – Load media files only when they become visible in the viewport.
• Use a Content Delivery Network (CDN) – Distribute content across multiple servers for faster global access.
• Enable HTTP/2 and HTTPS – Improve data transfer speeds and enhance security.
• Reduce main-thread work – Optimize JavaScript execution and minimize long tasks that block interactivity.

How to improve accessibility:

• Ensure text contrast meets WCAG standards – Improve readability for visually impaired users.
• Use descriptive alt text for images – Make visual elements accessible to screen readers.
• Optimize keyboard navigation – Ensure users can navigate via keyboard commands.
• Use semantic HTML – Structure content properly for assistive technologies.
• Ensure form fields have labels – Improve usability for users relying on screen readers.

How to enhance SEO and best practices:

• Optimize meta tags – Ensure title tags and meta descriptions are keyword-rich and engaging.
• Implement structured data (Schema Markup) – Help search engines better understand your content.
• Ensure mobile responsiveness – Test layouts across different screen sizes to maintain usability.
• Fix broken links – Remove or update dead links to improve user experience and search rankings.
• Secure your website – Implement HTTPS, update security policies, and avoid outdated libraries.

Step 4: Monitor ongoing performance and re-test regularly

Website performance is dynamic, requiring continuous monitoring and testing to ensure optimal efficiency.

Best practices for ongoing optimization:

• Schedule monthly Lighthouse audits – Regular testing ensures consistent improvements.
• Use real user monitoring (RUM) – Google Search Console’s Core Web Vitals report provides real-world data.
• Integrate automation tools – Use WebPageTest, GTmetrix, or New Relic for automated monitoring.
• Update assets and frameworks – Regularly optimize themes, plugins, and scripts to maintain efficiency.
• Optimize hosting and caching strategies – Upgrade hosting plans and fine-tune cache policies for better performance.
• Monitor third-party integrations – Limit excessive use of tracking scripts and advertising pixels.

Final thoughts

Google Lighthouse is a powerful, easy-to-use tool that provides deep insights into a website’s performance, accessibility, and SEO. By running regular audits, applying recommended fixes, and maintaining best practices, you can create a fast, efficient, and user-friendly website. Continuous monitoring and proactive improvements will ensure your site meets evolving web standards and remains competitive in search rankings.