Core Web Vitals - Google New Performance Indicators

Core Web Vitals - Google New Performance Indicators

It wasn't long ago that Google added new indicators to help improve the internet browsing experience. If you track or work with SEO and Web Performance, you're probably already aware of metrics called Core Web Vitals, and that's exactly what we're going to talk about in this article.

If you are a publisher, you should pay close attention to the next paragraphs. After all, we are talking about something that can greatly affect your revenues, which is the browsing experience of users. If the visitor to your site like what they see, the chance of them coming back and staying longer is higher.

So stay tuned for what we are going to present next!

The first question to be answered is: what are Core Web Vitals?

This term represents a set of indicators linked to three aspects of a web page:

  • Loading speed
  • Response time
  • Visual stability

According to Google, these three Key Performance Indicators (KPIs) will help websites evaluate the user experience in the best – and the most appropriate way possible.

However, that is not all!

Over time, these new indicators will have to be combined with existing factors, such as the existence of a web page compatible with mobile browsing (what we call a responsive website), providing a secure experience using the HTTPS protocol, and even not imposing intrusive interstitials – more about interstitial ads at this link.

The following image perfectly summarizes Google's willingness to integrate its Core Web Vitals into its existing KPIs as future metrics to evaluate the user experience:

Note that Core Web Vitals is currently composed of three indicators. Next, we will explain how each of them works in more detail.

Largest Contentful Paint (LCP)

The so-called LCP (Largest Contentful Paint) is the indicator that parameters the loading speed perceived by the user. This is a metric that takes into account the display time of the most important element seen on the screen.

LCP replaces other existing indicators, such as Load or DOMContentLoaded, that failed to have this concept of screen visibility. Thus, it is easier to understand how Google's metric works, especially if we take into account indicators such as First Meaningful Paint (FMP) and Speed Index (SI), two very complex indicators that, however, we can still find in the Lighthouse tool.


Google believes that a web page should show the most important element on the screen in the first 2.5 seconds to provide a good user experience.

For the analysis of the LCP, the following elements are evaluated:

  • The elements
  • The elements within a
  • The elements
  • Elements with an image loaded in the background using a url(_)
  • The Blocks of text

First Input Delay (FID)

The second metric of Core Web Vitals is First Input Delay (FID). This indicator takes the time it takes for the user to interact with the presented content. In this sense, Google recommends that the FID be less than 100 milliseconds.

The FID is the indicator that represents, in fact, the first impression that the site offers as a response to the user. And, as the saying goes, "the first impression is the last impression." Therefore, working the response time is crucial to perform well on Core Web Vitals and provide a good experience for those who visit the site.

This metric especially takes into account actions such as clicks, keystrokes, and touches on mobile screens.

Cumulative Layout Shift (CLS)

The last important indicator within Core Web Vitals is called cumulative layout shift (CLS). This metric is used to measure the visual stability of your site. But what does that mean?

Have you ever visited a page that had unexpected changes to the content format or started reloading without you asking? This behavior shows instability in the look of the site.

For CLS, the lower the score the nicer (and stable) the user's navigation. The indicator represents the sum of all individual scores for changes in page format for each unanticipated variation that occurs during the life of the page. This score must be less than 0.1 to represent a good metric in Core Web Vitals.

To calculate individual scores, Google uses the following formula:

layout shift score = impact fraction * distance fraction

How to improve these Core Web Vitals indicators?

That's the kind of question we might call a million-dollar question. After all, everyone wants to know how to improve the site, and make it faster and more attractive to users – so that they can come back more often and stay longer.

However, it is not easy to give a clear answer to this question.

The right thing is to say that it is possible to work with these indicators (and others) intentionally so that they improve. This is the scope of much of the work of those who act as Web Performance Testers or SEO, two professions that are gaining importance each day.

We intend to do specific articles on these issues soon and so we will not delve too much deeper here. However, the initial tip is: Learn how to monitor these metrics on your site and understand how each of them behaves with each change made to the page.

To do this, Google offers several developer tools, some more comprehensive than others, to keep track of your page's Core Web Vitals.


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