Site Performance: Understanding PageSpeed Insights

9 min read
Google PageSpeed Insights is a tool that tests your site page's performance for both desktop and mobile. This tool uses the Chrome User Experience (CrUX) report to analyze real visitor performance and Google Lighthouse to give your page a performance score.
Want to access PageSpeed Insights?
Click here to enter your page's URL and view your performance report.

Understanding your PageSpeed Insights score

When reviewing your PageSpeed Insights score, you can view different types of data depending on your site and needs. Your site's pages have separate Mobile and Desktop reports because the experience of your visitors may differ based on the device they use to view the site.

Google PageSpeed Insights has two distinct sections, each serving a unique purpose:
  • Discover what your real users are experiencing - Core Web Vitals Assessment: This section uses Field data to monitor the experience of your real site visitors. It is only available on pages that have a sufficient amount of traffic from real visits and interactions. 
A screenshot of the Discover what your real users are experiencing - Core Web Vitals Assessment metrics.
  • Diagnose Performance Issues - Performance score: This section uses Lab data to estimate the experience of your potential visitors. Google simulates a low-end mobile device with a slow internet connection to estimate the score.
A screenshot showing the Diagnose Performance Issues performance score metrics.

About the Core Web Vitals Assessment

The Core Web Vitals Assessment enables you to view the average metrics for the past 28-day period. Any modifications to your site will gradually influence the metrics each day until the full impact can be measured within 28 days. 

Field data offers the most accurate measure of your site's performance and pinpoints performance improvements you can take on your site. The Discover what your real users are experiencing section presents performance metrics gathered from actual visitors to your stie. 

The Core Web Vitals Assessment is released on a monthly basis, so improvements can take time to appear within the PageSpeed Insights. The field data is gathered from every Chrome session by visitors who have not opted out of reporting to Google.

Google's Core Web Vitals Assessment includes the following metrics:

  • Largest Contentful Paint (LCP): An indication of a site's loading time - more specifically, how long it takes for the largest content element in the site's viewport to load.
  • Interaction to Next Paint (INP): An assessment of your site's responsiveness to all click, tap, and keyboard interactions that occur throughout each visit on every page. The final INP value is the longest interaction observed. 
  • Cumulative Layout Shift (CLS): A measurement of unexpected movements of elements that change the layout of the page.
A screenshot showing Google's Core Web Vitals Assessment metrics.

Results of the Core Web Vitals Assessment

The results of your Core Web Vitals Assessment, gathered from the latest 28-day collection period, can vary based on the devices used and network connection. 

Click below to learn about each possible result:

SEO and Core Web Vitals Assessment

Core Web Vitals are an important indication of your site's performance, and one of the many measurements used to determine your site's SEO ranking. 

The performance SEO boost is applied to mobile and desktop pages separately. Each mobile page, and each desktop page can receive up to three boosts, one for each Core Web Vital:
  • Good: Metric scores receive a Full SEO boost (green)
  • Needs Improvement: Metric scores receive a Partial SEO boost (yellow)
  • Poor: Metric scores receive No SEO boost (red) 

For instance, a mobile page might get a partial SEO boost for LCP and INP, but a full boost for CLS.
A screenshot showing a partial SEO boost for LCP and INP, but a full boost for CLS.
While the desktop version of the same page gets a full SEO boost for each metric: LCP, INP and CLS. 
A screenshot showing how the desktop version of the same page might receive a full SEO boost for each metric.
Your Core Web Vitals Assessment will show as ‘Failed’ unless you receive a ‘Good’ score for all three Core Web Vital metrics. This does not mean the page hasn’t received a boost, as each metric contributes a boost independently.

Google Search always seeks to show the most relevant content, even if the page experience is sub-par. For most queries, there is a lot of helpful content available, so having a great page experience can contribute to success in search ranking.

Content remains the most important factor in maintaining your SEO score. We recommend optimizing your site's content, as well as updating your page's meta tags. Learn more SEO best practices.

Lab data and the performance score

To generate your performance score, Google uses Lighthouse, which is an open-source, automated tool for improving the quality of your web pages. Every time a page is analyzed in PageSpeed Insights, Google estimates the score based on simulated environments:
  • Desktop: Simulates a desktop Chrome browser with Google Lighthouse V11. 
  • Mobile: Simulates a Motorola “Moto G Power” mobile device, using a slow 4G internet connection.
If your page has sufficient traffic, we recommend focusing your efforts on the Core Web Vitals Assessment metrics. Real user data always offers a better understanding of your site visitors' experience during loading and navigation.

Your performance score is calculated using the following metrics:

  • First Contentful Paint (FCP)
  • Total Blocking Time (TBT)
  • Speed Index (SI)
  • Largest Contentful Paint (LCP)
  • Cumulative Layout Shift (CLS)
A screenshot showing the performance score metrics.

Mobile and desktop variations

Google Lighthouse, the tool that calculates the performance score, simulates mobile loading with the conditions of a mid-tier device (Moto G4) on a slow network (4G). For desktop, it simulates an emulated-desktop computer with a wired connection.  

The different scores on mobile and desktop are due to the simulated environments' varying processing power. 
PageSpeed also runs in a Google datacenter that can vary based on network conditions. You can find out where the test was done by checking the location in the Lighthouse Report's environment block.
A screenshot showing the location of a simulated environment.

Understanding Google's suggestions

In addition to presenting your Core Web Vital metrics and a Performance Score, the report also offers recommendations for improving your site's performance. These insights are divided into two sections:
  • Opportunities: This section provides suggestions for enhancing your site's performance. Each suggestion includes an estimate of how much faster the page will load if the recommendation is applied.
  • Diagnostics: This section displays extra information on how well a page is following best practices. 

Keep in mind that not all suggestions are applicable to your Wix site, such as removing unused JavaScript files. To optimize your site's performance and loading time, we recommend following our SEO best practices


Click below for answers to common questions about PageSpeed Insights reports. 

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