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How Google Lighthouse Helps Optimize Website Performance (2023)

A smooth, responsive, fast-loading site enhances user experience and bolsters trust and credibility. Missing out on these attributes could result in revenue loss and handing over potential customers to competitors with better-performing websites. 

Google Lighthouse has emerged as a crucial tool for businesses in their quest for website optimization. The following sections cover everything you need to know about Lighthouse and how it can help take your website’s speed, user experience, and overall quality to the next level.

What is Google Lighthouse?

Google Lighthouse is an open-source, automated tool designed to help web developers, SEO professionals, and website owners audit web pages and improve web page quality. It’s built into Google Chrome DevTools and is also available as a Node command line tool and Chrome extension.

Lighthouse auditsweb pages, providing performance scores and suggestions for faster loading. It analyzes page load speed, accessibility, search engine optimization (SEO), and more, equipping you with actionable feedback to improve key site performance indicators.

How does Google Lighthouse improve website performance?

Here are the performance metrics that Google Lighthouse uses to improve your website: 

Page load speed

Lighthouse provides Speed Insights, a measure of web pages’ loading speed and performance, and opportunities to improve.

Mobile performance

With Google prioritizing mobile sites, Lighthouse checks page speed on mobile devices and provides mobile-specific suggestions.

Core Web Vitals

Lighthouse measures and provides recommendations to improve Core Web Vitals, Google’s key metrics for user experience, which include loading, interactivity, and visual stability.

Progressive web apps

Lighthouse checks if your site’s web applications meet progressive web app (PWA) criteria, which facilitate features like offline browsing and fast load times.


Lighthouse analyzes accessibility, helping you optimize site usage for all users, including those with disabilities. 

SEO optimization

Lighthouse verifies on-page SEO, providing insights that can help you keep your web pages optimized for discoverability and ranking in search engines.

How does Google Lighthouse work?

Google Lighthouse works by simulating real user experiences. Here’s how Google Lighthouse analyzes pages:

  1. Lighthouse is run on a page URL on local sites or live sites. 
  2. The tool first visits the page as an anonymous user, checking factors like network reliability and processing capabilities.
  3. As the page loads, Lighthouse observes and collects data about the page experience, including metrics like resource and page load times.
  4. Lighthouse analyzes the data against predefined standards covering web performance, accessibility, SEO, progressive web apps, and more.
  5. Each audit gets a score from 0 to 100. The overall performance score calculated is based on a combination of the individual audit scores, which are all weighted differently in importance.
  6. Lighthouse repeats this process for mobile user experiences.
  7. Finally, Lighthouse generates a report with the page’s overall scores, individual audit scores, performance metrics, and improvement recommendations. The analysis provides objective metrics and actionable suggestions for creating the optimal site experience on all devices.

How to use Google Lighthouse

  1. Run Google Lighthouse reports
  2. Interpret Google Lighthouse reports
  3. Use Google Lighthouse audit feedback

Assessing and enhancing web page quality can be challenging, but there are three ways you can use Google Lighthouse to optimize your site for user experience and search engine visibility.

1. Run Google Lighthouse reports

You can install Lighthouse and run it through Chrome DevTools, Chrome extensions, or the Node.js command line. Here are the steps for these various options:

Run a Lighthouse report in Chrome DevTools

1. Open the web page you want to audit in Chrome.

2. Click on the three vertical dots in the top right corner and select “More tools.”

3. Select the “Lighthouse” tab.

4. Check the box for the categories you want to audit, like performance, accessibility, SEO, etc.

5. Click “Analyze page load.” Lighthouse audits the page and provides a report with scores and suggestions.

    Run a Lighthouse report in Chrome Extension

    1. Install the Lighthouse Chrome extension.

    2. With the Lighthouse extension enabled, click on its icon in Chrome to launch Lighthouse and audit any open tab.

    3. Use the configuration settings to select desired categories and device types.

    4. Click “Generate report” to run the Lighthouse audit.

      Run a Lighthouse report using a Node.js command line

      1. Install Lighthouse globally via “npm install -g lighthouse.”

      2. Run “lighthouse <url>” in the terminal to audit a site.

      3. Additional CLI flags can be used to select categories, output type, device type, and more.

      4. Lighthouse audits the page and prints the report in the terminal.

        2. Interpret Google Lighthouse reports

        Google Lighthouse splits comprehensive reports into various categories, each with valuable insights into different aspects of your website. Let’s break down the metrics and how to interpret them for each category:


        The performance section highlights how your website performs in terms of loading speed, interactivity, and stability. You’ll find scores for metrics like First Contentful Paint (when the first text or graphic is rendered) and Cumulative Layout Shift (the visual stability of a web page). A high performance score (90 to 100) indicates optimal performance. Lower scores (50 or below) indicate areas requiring significant improvement in loading and interactivity.


        Accessibility evaluates how user-friendly and accessible your website is—especially for users with visual impairments. It includes checks for image alt attributes (image descriptions for accessibility), contrast ratios, and screen reader capabilities. A high score implies your site is broadly accessible, while a lower score signifies potential barriers for some users, risking non-compliance with web accessibility standards.

        Best practices

        The best practices category assesses standard best practices in web development, covering areas like HTTPS usage, image aspect ratios, and avoiding deprecated APIs. A high score means you’re following recommended web standards. A lower score indicates some areas could benefit from updated practices or technologies.


        Lighthouse checks how well your website is optimized for search engines. This can include metadata presence, legible font sizes, and HTTP status codes. A high score suggests your website is optimized for search engine visibility, whereas a lower score points to missed SEO opportunities that, if implemented, could enhance your online visibility as a business.

        Progressive web apps (PWA)

        This section evaluates your website’s ability to offer app-like experiences on mobile devices or desktops. PWA combines the best of web and mobile apps by making web applications function offline and load instantly. The PWA section checks your site for characteristics like responsive design. A high PWA score signifies a seamless app-like experience. Lower scores indicate the area needs improvement to align with PWA standards.

        3. Use Google Lighthouse audit feedback

        You can go one step deeper with the metrics provided in the report. Within the categories outlined above, Lighthouse further breaks down its feedback into these sections:


        This section suggests potential fixes to improve your category score. For instance, reducing image sizes can improve your site’s performance.


        This section provides more detailed information about your web page performance and why certain items may be causing slowdowns or issues.

        Passed audits

        This section lists what your website is already doing well.

        Additional items to manually check

        Automated testing has its limits. Lighthouse sometimes suggests manual checks to ensure all aspects are covered.

        Google Lighthouse FAQ

        How do I enable Lighthouse in Chrome DevTools?

        Lighthouse is built into Chrome DevTools, under the “Lighthouse” tab. Make sure you have the latest version of the Chrome browser for the tool to operate properly.

        Should I run Google Lighthouse in incognito mode?

        Yes. Run Google Lighthouse audits in Chrome’s incognito mode to emulate a first-time user’s experience on the site. Extensions and cookies can modify page behavior.

        Can you use Google Lighthouse for mobile performance analysis?

        Yes. Lighthouse provides a mobile performance audit for analysis on mobile devices. You can also choose device types when running Lighthouse.

        What are some common issues Google Lighthouse can detect?

        Some common problems include excessive HTTP requests, unused JavaScript, insecure connections, improper SEO tags and meta descriptions, and inaccessible elements.

        Is Google Lighthouse only for performance analysis?

        No. Google Lighthouse also audits for SEO, accessibility, best practices, and progressive web app criteria. Performance and user experience optimization are its primary focus areas.

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