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How to Optimize Website Performance with Google Lighthouse

Lighthouse is a free and open-source tool by Google that measures the quality of web pages. The tool runs tests for website performance, accessibility, and search engine optimization. It is mainly developed to help web developers but can be helpful for SEO specialists and even website owners with no technical skills as well.

How to Optimize Website Performance with Google Lighthouse article image

All Lighthouse metrics are an indication of how fast a site performs for actual users – mobile and desktop. And if you run a business that is online, you should definitely care about performance. Well performing sites are profitable sites.

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What is Google Lighthouse?

Google developers team has created Lighthouse with the intent to enable web developers and site owners to receive clear and actionable site performance reports. All data in Lighthouse is prioritized in accordance with its level of importance. A considerable advantage is that the data generated in Google Chrome is powered by the performance recorded on the machines of real users around the globe (all collected metrics are aggregated anonymously).

Lighthouse is designed to run site tests for the following categories:

  • Performance
  • Accessibility
  • Best Practices
  • SEO
  • Progressive Web Apps
  • Publisher Ads

Each audit generated by Lighthouse has a reference doc that explains why the audit is important, as well as how to fix it.

Google Lighthouse Metrics

Analysing all Google Lighthouse metrics can be a very overwhelming process, especially for non-tech savvy users. That’s why we decided to take a look at the major categories which reveal all metrics that need to be fixed or improved in order that a website can run faster, be optimized and easy to navigate:


In general, the Performance category tracks your website’s loading speed as it is one of the most important ranking factors. You can see the speed progression of your website load in a frame by frame format. When Lighthouse finds that the loading speed has to be improved it provides solutions on the Opportunities section of the report.


This review section presents you with different opportunities to make your website more accessible to your users. When metrics under the Accessibility section are optimized it means that your website has a solid and presentable structure with well-defined attributes. With Google shifting to a mobile-first approach, the optimization of these factors ensures that the mobile version of your website would bring you the best results.

Best Practices

The Best practices section shows the best methods to optimize your website’s performance. It also highlights the positive points that you have already accomplished. No matter how negligible these technical factors may seem, they are crucial in providing a solid online experience. The category reveals recommendations for prominent security practices as well as proper ways for image representation. These recommendations eliminate some performance issues and provide for a smoother website that SEO optimized.


The SEO section audits how your website performs in search engines. Lighthouse uses Google’s ranking factors to evaluate the optimization level of your website. Some of the most important search rankings factors are getting into account including crawling and indexing, mobile-friendliness, and content quality. However, there are additional factors Lighthouse does not check that may affect your search ranking.

Lighthouse Updated to Version 6.0

The online giant Google has announced an update of its Lighthouse engine earlier this year. The SEO test tool is now running version 6.0. Lighthouse 6.0 introduced three new metrics to the report. Two of these new metrics – Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS) – are lab implementations of Core Web Vitals. Without going any further we will say that as described on Google Web Dev site:

LCP provides a signal to developers about how quickly a user is actually able to see the content of a page. While CLS quantifies how much a page’s content visually shifts around.

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How to Test Website Performance with Google Lighthouse (Speed, SEO, Accessibility)

With site speed becoming one of the most important ranking factors testing how fast a site needs to load appears to be an essential optimization process. Various researches reveal that nowadays it is a matter of one-second delay in load time for a user to leave a given website. The longer it takes for a site to load its content, the less traffic it is likely to gain. The less traffic a website gains, the fewer customers it will have. Site speed and performance can have a direct impact on business success.

So the question is now whether you need to test your site performance or not, but how to do it as soon as possible. The current status of a web page/website is very important to be measured. Is it performing well, good or poor? You can understand a number of important details about how well your website performs by using Google Lighthouse.

Test Website Performance with Google Lighthouse

With Google Lighthouse you can reveal data that regards not only to your site speed but its performance, accessibility and SEO as well. To get a report on all these and even more site metrics you should have a Chrome browser installed on your device.

One way to use the Lighthouse engine is to access it through the Chrome Dev Tools. This can happen directly in your Chrome browser – you just need to open the page you want analysis for, press Command+Option+C (Mac) or Control+Shift+C (Windows, Linux, Chrome OS).

Important note! In order that the tool can generate a proper report about a web page/website performance, you need to perform the test via add-ons free web browser or via Incognito mode.

open lighthouse in chrome web browser

On the left side, you will see a viewport of the page that will be audited. On the right will appear the Audits panel of Chrome DevTools, which is powered by Lighthouse.

lighthouse categories desktop mobile reports

When you see the list of audit categories check the ones you need and Run audit. From 30 to 60 seconds later, Lighthouse will display you a report on the page.

google lighthouse website performance report in chrome

Every Lighthouse audit is detailed enough to help you improve metrics or add what is missing. Next to every metric you can see a learn more link that will open a descriptive page on the given metric.

performance metrics stats and descriptions

Google Lighthouse Extension

For people’s convenience Lighthouse can be used as a browser extension as well. Lighthouse extension is available for both Chrome and Firefox web browsers.

google lighthouse extension chrome

So if you are one of the users who want to run speed tests with Lighthouse extension you just need to find it in Chrome Web Store respectively Firefox Add-ons, add it to the selected browser, and navigate to its interface.

firefox add-ons google lighthouse test speed

The Lighthouse extension is designed to appear in a very similar way to its browser look. So you can monitor website metrics and consider fixes by following the website performance steps for Chrome listed above.

Test Site Speed With Google PageSpeed Insights

PageSpeed Insights is another online based tool that lets you run performance tests for every URL you want. It generates Lab and Field data on the page’s crucial speed elements. The Field data is based on Chrome users’ experience. While the Lab data presents both performance metrics and suggests opportunities and further diagnostics on website speed optimization. It is noteworthy that all metrics shown under the Lab data are powered by Lighthouse. Reports can be again performed for mobile and desktop website versions.

One of the first things you are going to see in a report by PageSpeed Insights is the score indication metrics. It is the same score users will find in the Google Lighthouse project.

pagespeed insights website performance report

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Final Thoughts

The practical knowledge about website optimization guarantees higher customer satisfaction. Those who know how to optimize website performance with tools like Google Lighthouse are happy to gain higher conversion rates, record more time spent on pages and earn a lot of money.

If you have questions about SEO tools or want to share your experience with website development and optimization, leave a comment below and let’s talk.

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