Google Lighthouse: what it is and how it works

Google Lighthouse is an open-source web page optimization tool. A simple, intuitive, and complete tool to improve the quality and performance of a site.

Periodically analyzing a website is essential to make it more visible and usable for the user. For this purpose, Google has made the Lighthouse, available to webmasters and SEO experts, capable of measuring and optimizing the online performance of sites, such as loading speed and user experience.

Want to learn more about the Google Lighthouse? Then read on, I will explain:

  • what is Google Lighthouse used for;
  • why it is important to use it;
  • how Lighthouse works;
  • what checks it can perform.

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What is Google Lighthouse and what is it for

Google Lighthouse is a free and automatic tool that allows you to measure and improve the performance of an Internet site in terms of speed, quality, and usability.

In a single simple and intuitive interface, it solves various needs: SEO analysis, HTML, graphics, performance, and website construction quality. It is a useful tool for carrying out personalized checks through which to monitor and optimize the functioning of sites and blogs.

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Why the Google Lighthouse tool is important

A website is visible on search engines when it is well SEO-optimized, has good loading times, and is usable by the user. To guarantee these conditions it is essential to analyze them periodically. Having a tool like Lighthouse available which, free of charge and in a completely automatic way, scans the site and identifies its deficiencies and aspects for improvement, is a considerable help.

So, this Google platform is important because it allows you to improve the efficiency of your web project, which is even more relevant when it comes to local SEO.

How Lighthouse works

For each resource analyzed, the Google Lighthouse service provides a report containing various useful information, divided according to the tests performed. The tests, called audits, are grouped into five categories:

  1. Performance,
  2. Best Practices,
  3. SEO,
  4. Accessibility,
  5. Progressive Web Apps.

For each analysis category, the Lighthouse tool returns an overall score, ranging from 0-100. The scores are indicative of the state of health of the website. If they are low it means that the website is of poor quality and that work must be done to improve it. Conversely, if they are high it means that the site is:

  • Fast and performing,
  • Safe,
  • SEO optimized,
  • Designed according to user experience guidelines,
  • Mobile-friendly.

Together, all these factors improve the site’s ranking on search engines, increase its visibility and trigger many other benefits.

Using the software is very simple; keep following me, I’ll explain step by step how to use it to the fullest!

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Log in to the platform

The ways to access the Google Lighthouse platform and take advantage of the audits are different; you can do this through Chrome DevTools, Chrome Extension, PageSpeed Insights, or Google’s WebDev.

Do you want to understand which is the most suitable solution for you? Let’s see them together! Before doing so, however, know that the prerequisite for being able to view the report generated by the Google Lighthouse is to have Google Chrome installed on the browser.

Chrome DevTools

The easiest way to activate the Lighthouse suite is through the Developer Tools or Chrome DevTools. To access it, follow these steps:

  1. Type in the browser (Chrome) the URL of the site you want to analyze;
  2. Press the right mouse button on the screen and select the “Inspect” item;
  3. Click on “Lighthouse” to open commands in Chrome DevTools.

Alternatively, after typing the URL of the resource, you can type the combination CTRL+SHIFT+I on the keyboard. This will directly open the Lighthouse panel.

google lighthouse in chrome devtools

Chrome Extensions

You can run Google Lighthouse audits using the Lighthouse Chrome Extension, a Google extension. Here’s how to proceed:

  1. Go to the Chrome Webstore and install the Lighthouse Google Extension;
  2. Type the URL of the site you want to analyze into your browser;
  3. Press the icon at the top of the Chrome bar.

platform lighthouse chrome extensions

PageSpeed Insights

Previously, Google PageSpeed Insights did not provide comprehensive results when analyzing a site’s performance; now this tool has integrated Google Lighthouse functions. To use the tool:

1. Log into PageSpeed Insights
2. Enter the URL of the site to be tested into the browser.

pagespeed insight tool

WebDev by Google

Google Lighthouse audits can also be performed through a Google online portal: WebDev. To access it:

  1. Enter web. dev
  2. Enter the URL of the site you want to analyze into your browser.

webdev by google

Run the Google Lighthouse website test

Have you chosen how to access the Lighthouse suite? If you are in doubt, I suggest you do it using the first method I told you about, i.e. Chrome DevTools. So you can start the audits directly from the site of your interest.

Compared to other solutions, which provide you with test scores for all five categories, you can customize the analyzes by selecting only the items of your interest. Furthermore, you can have the reports for both the desktop and mobile versions of the site, obtaining a complete, clear, and detailed overview of its performance.

If you decide to opt for this solution, after typing the URL of the resource you want to analyze, open Lighthouse by following the steps described above. Once you have decided whether to generate the report in full or in part, for the desktop and/or mobile version, press the “Generate report” button.

Even in other cases, the procedure for obtaining the report is simple: whether you open the tool before or after typing in the address of the resource to be analyzed, to start the audits you must always click on the analysis start button.

Analyze the results

The Google Lighthouse report returns overall scores for each of the 5 categories (Performance, Best practices, SEO, Accessibility, and Progressive Web App) ranging from 0-100, as well as specific evaluations for the various audits performed.

These scores are important for website optimization and are awarded based on the satisfaction of the parameters (audits).

google lighthouse report


In this category, Google Lighthouse analyzes the website loading speed; in particular, there are 6 parameters that it takes into account:

  1. First Contentful Paint (FCP): The time before text or images appear;
  2. Speed Index – the loading speed of the page content;
  3. Largest Contentful Paint – The loading time of the largest content;
  4. Time to Interactive: the time that passes before the user can interact;
  5. Total Blocking Time: The sum between FCP and Time Interaction must not exceed 5 seconds;
  6. Cumulative Layout Shift: measures the movement of visible elements within the window.

The report also includes tips to help you speed up your site and other performance information that doesn’t have a direct effect on your score.

devtools report lighthouse performance

Best Practices

This entry looks at the security aspects of the site. The report returns 16 audits in total. Among the most important we find information regarding:

  • the use of the protocols used (HTTPS and HTTP/2);
  • database security;
  • mistakes;
  • the libraries;
  • unsafe links.

lighthouse best practices


These checks ensure that your web page was built following search engine optimization best practices. The SEO category in Lighthouse returns 14 audits; among the most important information we find:

  • Mobile friendly;
  • Title and Meta Description;
  • Text size;
  • The Alt attribute in images;
  • Internal links (Anchor text);
  • The correct Robots.txt file instructions;
  • Canonical and Hreflag optimization.

seo category in lighthouse


Google Lighthouse focuses on the usability of the site by the user. A website must be optimized for search engines, but also designed according to user experience guidelines.

Aspects such as color contrast between colors, the presence of tags, buttons, links, and more are analyzed. In summary, the report provides a snapshot of all those good practices that make a site always consultable and in the best possible way.

accessibility google lighthouse report

Progressive Web Apps

The Progressive Web App (PWA) category analyzes site scalability, accessibility, and mobile navigation.

Users can download web pages on their mobile devices and access them even offline; once downloaded, they act like applications. The final report contains information aimed at improving and speeding up behavior on the web, as well as aspects concerning the quality of mobile navigation.

google information progressive web apps

Conclusions and request more information

As you may have understood, Google Lighthouse is a tool that offers important information on aspects for optimizing web pages. In this article, I have tried to explain to you what it is, why it is important, and how it works. The main features of the tool, those for which it should be used, can be summarized in 4 points:

  1. it’s free;
  2. offers an immediate understanding, the analysis is divided into audits (specific areas);
  3. allows you to understand the main difficulties underlying the positioning;
  4. allows you to measure and improve the performance of an Internet site in terms of speed, quality, and usability.

What are you waiting for? Start testing this analysis tool on the sites of your interest so you can realize how useful it can be. But remember that it is not enough to analyze the website once; the analysis must be done constantly to allow continuous optimization.

You understand how to use Google Lighthouse, take another step forward and start studying digital marketing



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