PageSpeed ​​Insights: what is this tool?

PagesSpeed Insights performances du site AntheDesign

Google PageSpeed ​​Insights is a free and powerful tool based on analyzed technical data:

  • laboratory data,
  • and field data.

Explanations on its operation, its advantages and the corrections to be made to your site.

What is PageSpeed ​​Insights?

PageSpeed ​​Insights, also known as PSI, is a performance test tool offered by Google. The tool, for example, analyzes a URL of your web page and provides a precise report on the points to be improved to optimize the loading speed of this same page.

Google PageSpeed ​​Insights performs an analysis of the page data in order to render a detailed report. It gives a score ranging from 0 to 100:

  • from 0 to 49, the score is red;
  • from 50 to 89, the score is orange;
  • and from 90 to 100, the score is green.

google pagespeed insights tricolor barometer

It also provides statistical data and web performance data.

PageSpeed ​​Insights and Core Web Vitals

To give a performance score, it takes into account different statistics and laboratory data that are part of the Core Web Vitals.

Indeed, the tool analyzes:

  • First Contentful Paint (FCP),
  • the First Input Delay (FID),
  • Largest Contentful Paint (LCP),
  • as well as the Cumulative Layout Shift (CLS).

This is the set of Core Web Vitals, in French, the Essential Web Signals.


Expressed in seconds, it symbolizes the time elapsed between the start of loading the page and the moment when the first element appears on the page on the screen. The FCP must be less than 1.8 seconds and especially not exceed 3 seconds.


The First Input Delay measures the response time of the page between the moment when the Internet user interacts for the first time on the analyzed page and the moment when the page responds to his request. To be efficient, the time must be less than 100 ms.

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Also expressed in seconds, it measures the time required for the page to load and therefore its performance for loading the main elements of the page. The faster it is, the better. This score must be less than 2.5 seconds to be effective and must not exceed 4 seconds.


The Cumulative Layout Shift, on the other hand, measures the visual stability of the analyzed page. The CLS score is bad when you click on a link and a block appears (pop-up window, screen shift, annoying advertisement, etc.). This type of block often causes frustration for the Internet user. If the score is high, it means that the phenomenon occurs too often. This score must then be less than 0.1 and not exceed 0.25.

What other data is collected by PageSpeed ​​Insights?

Google PageSpeed ​​Insights also takes into account performance statistics (from the Lighthouse tool) and field data such as:

  • the interaction time (Time to Interactive). It is decisive for the user and his experience, it is considered good when it does not exceed 50 milliseconds;
  • the page display speed (Speed ​​Index). It is a benchmark indicator for estimating good user experience and web performance. The faster it is, the better it is for the Internet user. It is considered fast if it is between 0 and 3.4 seconds;
  • the blocking time (Total Blocking Time, TBT). It measures the time between the FCP and the interaction time (TTI). Concretely, it is determined by the execution time of a task: if it is too long, this time will be long (above 50 ms); if it is executed quickly, the time will be better (below 50 ms).

Finally, at the bottom of the page, the tool provides opportunities for areas for improvement to optimize the overall loading speed of the page.

google pagespeed insights tips for optimizing websitegoogle pagespeed insights tips for optimizing website

Since PageSpeed ​​Insights is operated by Google, the world’s largest search engine, it is obvious that the advertised score has an impact on SEO and your page’s ranking in the search results (SERP). It is therefore not to be neglected or ignored but indeed to be taken into account if you want to optimize the loading speed. However, this does not guarantee to get a top spot in the SERP because SEO is not based solely, and fortunately, on this score alone.

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What are the goals of PageSpeed ​​Insights?

The tool makes it possible to measure the performance of a web page as well on mobile and tablet as on a computer. It measures above all the loading speed of the page and offers advice to improve this time which strongly favors the bounce rate, and directly impacts SEO.

In addition to this, it also gives other elements necessary to improve the technical aspects of its web page.

These collected data give rise to an analysis of various technical points to be improved:

  • JavaScript,
  • HTML,
  • CSS,
  • image size and optimization,
  • number of redirects …

By correcting these points identified by Google PSI and following its recommendations, you improve the display speed of the analyzed page.

The advantages of PSI are to improve its loading speed

By using PageSpeed ​​Insights and taking its advice into account, you improve your loading speed. The loading speed is decisive for the user experience: the faster the page loads, the better the experience.

By reducing the loading speed:

  • the bounce rate is minimized which is, otherwise, detrimental for any website and for its web performance;
  • you increase the conversion rate: the longer the Internet user stays on the site, the more chance you have of converting him;
  • you speed up the crawl speed of crawlers;
  • the indexation rate is increased;
  • you improve your natural referencing (SEO).

How to improve your score on Google PageSpeed ​​Insights?

To improve your PSI score, several actions are possible and are recommended by the tool such as:

Reduce JavaScript and CSS resources

To improve page load time, scripts really weigh down a web page and can even block it so they should be used sparingly so as not to have a negative impact on your site.

Minify CSS

CSS is often too large; for this, you (or your webmaster) must condense the CSS files by removing duplicates, spaces, unnecessary characters.

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Choose images with better optimization

Images also require loading time: so opt for better optimization and a better format to reduce their impact on loading time. Note that the WebP format is highly appreciated, unlike JPEG, and maximum compression highly recommended.

Prefer videos rather than GIFS

GIFS are original visual content but which take a long time to load, unlike video files deemed to be smaller. The MP4 format remains heavier but compatible with all browsers, while the WebM format is the most optimized for the web but unfortunately remains less compatible with certain browsers.

Reduce the number of existing redirects

Reducing redirects is essential as much as possible because the user loses precious seconds and loading delays are experienced if there are too many redirects.

Opt for the activation of GZIP text compression

This allows the browser to go to a reduced version of the pages and considerably optimize the display of a web page.

Apart from these aspects, the server response time must also be ideal, ie less than 600 ms. If the time is greater than 600ms, PSI will let you know.

The change in PageSpeed ​​Insights

Recently, Google PageSpeed ​​Insights had a clearer and more intuitive update under the URL: But that’s not all: Google, which deploys PSI, now relies on Lighthouse. This free tool aims to improve the quality of internet pages and is accessible from Chrome DevTools.

This change leads to the distinction between laboratory data and field data:

  1. the first come from Google’s servers, created under fixed conditions;
  2. seconds are based on mobile user experience and data collected from your visitors over the past 28 days and over time.

Thus, the data may be different, but it provides a better understanding of the bugs and the opportunities to be fixed.

To conclude on PageSpeed ​​Insights

Google PageSpeed ​​Insights is an excellent tool for improving the performance of your web pages. Loading speed and web performance remain, and should remain, essential elements in SEO and in the user experience. These metrics help you dramatically improve the current state of your site and how it works, don’t miss it!

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