Google Lighthouse: What Is It & How to Use It?

Google Lighthouse: What Is It & How to Use It?

As a site owner, you would have tried various tools to improve your site’s performance and ranking. You may have conducted multiple audit checks that focused on content type, keywords, and so on. But what if you were told that there is a tool that allows you to see your site in the same way that Google does? Meet Google’s most effective tool—Lighthouse.

If you are unfamiliar with this tool, or have never used it, here are some things you should know.

What is Google Lighthouse? 

Google Lighthouse can help you improve the website’s responsiveness, performance, speed, and overall experience. The reports generated by this tool can help you identify the areas in which your website needs the most fixing. 

Since it is a Google tool, it is one of the finest and most reliable ways to figure out how Google perceives your page. Recently, Google introduced Core Web Vitals signals. Use the Googel Lighthouse tool in conjunction with Core Web Vitals to gain a better understanding of your page’s performance.

You can run this tool in one of these ways.

  • Chrome Developer Tools
  • A Chrome extension
  • A Node module
  • A Web User Interface (UI)

Core Web Vitals 

Core Web vitals include certain aspects that Google thinks is important for improving the user experience on your Web page. It consists of three key components:

  • Largest Contentful Paint (LCP): 

It analyses how long your page takes to load from the user’s standpoint.

  • Cumulative Layout Shift (CLS):

It measures page stability. If the CLS score is high, it indicates that the elements on your page move a lot while loading.

  • First Input Delay (FID):

It measures the time the user takes to interact with your page. Interaction includes clicking links, scrolling down the page, and so on.

What to check with Google Lighthouse?

Google Lighthouse is the ideal tool to measure your site’s Core Web Vitals. It performs a site audit and reviews the responsiveness of your website by taking into account the average user’s device and Internet connection speed. The report generated by this tool gives you an idea of where better user experience needs to be created. 

Using Google Lighthouse

Using Google Lighthouse is not difficult. This tool is available in three distinct workflows:

Chrome Developer tools 

Here’s how you can use Google Lighthouse in Chrome Developer Tools.

  • Install Google Chrome. Always remember that the Lighthouse function is exclusively for desktop computers and not for smartphones.
  • Next, open Google Chrome and go to the page on your site that needs to be audited.
  • Click the right button on the mouse and select Inspect from the menu.
  • Clicking Inspect displays a panel at the bottom of the page. Click the Lighthouse icon on the toolbar of the panel. If you are having trouble finding this tool, simply click the two arrows at the bottom of the toolbar.
  • The panel takes you to the Google Lighthouse tool. There, you can click Generate Report. 

Here are the three basic steps you may follow to make it easier for you to access the Google Lighthouse Tool.

  • In the address bar of the Google Chrome browser, right-click the three vertical dots to assess the menu. 
  • From the menu displayed, select  ‘More Tools.’
  • Then select ‘Developer Tools.’

Chrome Extension 

  • Download Google Chrome and go to the Google Chrome Web Store.
  • Download the Google Lighthouse extension from the Web Store and install it.
  • Once the installation is complete, restart the browser.
  • Click the Google Lighthouse icon which has appeared on the address bar.
  • Select ‘Generate Report’ from the menu displayed.

Following the report generation, you can plan the strategy for improving the performance of the Web page.

Lighthouse vs PageSpeed Insights 

The key difference between Google’s PageSpeed Insights and Google Lighthouse is the data they use to evaluate page performance. Lighthouse evaluates a page’s user-friendliness by utilising only the lab data. On the other hand, the reports generated by PageSpeed Insights are based on real-world data from lab and the Chrome User Experience report.

Real-world data is more relevant because it is sourced from actual Google Chrome users. Using this information, you can quickly determine how long it takes for your website to load on a real user’s device. Lab data, on the other hand, is prepared using specific device specs and a predetermined network.

Performance Metrics Used by Google Lighthouse 

These are the parameters that Google Lighthouse uses to evaluate page performance.

  • Largest Contentful Paint (LCP)

LCP accounts for 25% of the total Lighthouse score. It calculates how long it takes for your Web page’s largest text block or image to load and appear within the viewport. The key elements that LCP considers are background images, videos, regular images, and texts. If you are a site owner, try to achieve an LCP of fewer than 2.5 seconds. If your LCP score is poor, focus on the following.

  • Server optimisation
  • Cache assets
  • Routing your users to the nearest content delivery network (CDN)
  • Total Blocking Time (TBT)

TBT accounts for 30% of the total score. It measures the time duration between Time to Interactive and First Contentful Paint (FCP). As a site owner, make sure that your TBT score is below 300 milliseconds. It usually measures tasks that take more than 50 milliseconds. You can resolve TBT issues by breaking up the long tasks, using Web workers, and so on.

  • First Contentful Paint (FCP):

The time it takes for the very first image on your screen is what FCP measures. It accounts for 10% of Google Lighthouse’s total score. Having an FCP score of fewer than two seconds is considered good. 

Four Speed Tips from Google Lighthouse

1) Eliminate Render Blocking

Render blocking is one of the major reasons for your site visitors’ annoyance. When someone visits your website or clicks a page, their browser follows a specific pattern. It starts by sending queries, then downloads the JavaScript and external CSS files, and finally processes them. This entire process is regarded as render blocking. Once the render blocking process is completed, visitors can explore your website or buy goods from it. CSS and JavaScript files are also known to slow down your site speed. The scenario contributes to the rise in the bounce rate. 

Therefore, for JavaScript, add important pieces to HTML inline. You may also go for a sync of non-critical aspects to help with easing out loading delays. In the case of CSS files, you can parse the file using a media query string. Under this method, each HTML style sheet link has its own media file. It assists in the execution of specific tasks that are needed by the user’s device.

2) Deliver Smaller Payloads 

You may also compress or minify the file size to get better results. For example, when you choose minification, the file’s code characters are shrunk such that it remains unaffected by how the browser processes it. On the other hand, compression reduces the file size in the same way that zipping does.

3) Optimise Images 

Many site owners believe optimisation means compromising on image quality. This is not true. Image formats such as WebP, JPEG 2000, and JPEG XR are noted for high-quality visuals at higher compression ratios. If you are using such formats in your content, the page load time will improve significantly.

You may also opt for responsive images. The load time for such photos is well-defined in advance. You can create different responsive images for each image. By selecting the one that is best for your page, you may reduce load time while also enhancing customer satisfaction.

4) Extend Browser Caching 

The browser your site user uses stores the data/file for a temporary period. Regular storage is advantageous for repeat visits because it improves user experience. When the same visitor returns to your site, their browser loads the cached copy until the cache period for these files expires. After that, the Web browser requests a newer version to start the caching process again. However, if you update your entire site, there is a high chance that your company’s development team invalidates the old cache. Therefore, it is advisable to extend browser caching.


To summarise, Google Lighthouse is the tool to utilise if you want to improve the user-friendliness of your website. It can assist in identifying faults in page performance, image optimisation, video optimisation, and other areas. You may also use this tool to prepare a search engine optimisation (SEO) strategy for the future. 

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Google Lighthouse: What Is It & How to Use It?