What are the Core Web Vitals

Google introduced in 2021 a new ranking factor for its search engine: The Core Web Vitals.

The goal of Core Web Vitals is to measure the actual user experience. These signals include loading performance, interactivity and visual stability of the page.

Core Web Vitals consist of three main signals:

Largest Contentful Paint (LCP)
First Input Delay (FID)
Cumulative Layout Shift (CLS)

Let’s discover what the Core Web Vitals are, how they are measured, and if they are essential for your SEO.

Table of Contents

What are Core Web Vitals, and what do they measure?

In a nutshell, the three metrics of the Core web vital are:

LCP: The time to see the first elements of the page. It gives a feeling of speed.
FID: The time for the first interaction (like a click). It indicates potential user frustration if it is too slow.
CLS: Visual stability to avoid any “Where is the paragraph I was reading? S*** I have to scroll down again” feeling by your visitor

Your website will pass the Core Web Vitals if you score green. Green is good.

Let’s take a closer look at what’s behind Largest Contentful Paint (LCP), First Input Delay (FID) and Cumulative Layout Shift (CLS) and how Google measures them.

Largest Contentful Paint (LCP)

Largest Contentful Paint (LCP) measures page loading performance. To be more precise, LCP measures the perceived loading speed, i.e. how long it takes for your page to display the first elements that are important to the user.

The first element could be the title of an article and its banner image.

LCP does not measure the complete loading of the page but only the loading of time of what you see on the screen. You need to understand this difference.

To provide a good user experience, sites should strive to display the first “frame” of the content within 2.5 seconds.

It is Google’s standard. But we all agree that it’s more pleasant to have content that displays directly – no one likes to see blank pages.

A web page is displayed in stages. So in the early stages, the top of your page loads. Once the main elements are displayed, the LCP will be reached. That’s it!

A fast LCP allows you to “convince” the user about the interest of your page. The first few seconds are crucial to avoid a “bounce back”.

Keep in mind: Google considers the dwell time as a ranking signal, so it is better to keep visitors on your site.

First Input Delay (FID)

The First Input Delay (FID) measures the “responsiveness” of a page. It measures the time between when a user first interacts with your page (i.e., when they click on a link or button) and when the browser can respond to that interaction.

You have an excellent FID if the interaction with your page (like clicking a button) takes less than 100ms to trigger the next action.

The FID can be seen as measuring user frustration. Indeed, nothing is more frustrating than sending a form or clicking a button that takes seconds to trigger the next step.

Zero frustration equals a near-zero FID. Or the other way around…

Cumulative Layout Shift (CLS)

The Cumulative Layout Shift (CLS) measures visual stability, and the frequency users experience unexpected layout changes.

A visual change occurs every time an element on your page changes its position unexpectedly.

Here is an example of a visual change: You are reading a paragraph, and suddenly it disappears. The section is replaced by a button (which has just finished loading). You need to scroll down to resume reading.

The CLS calculation is based on various examinations and movements of elements within the browser while the page is loading.

You have to have a score close to zero to be considered excellent.

How Google measures the Core Web Vitals

Yes! The Core Web Vitals data are coming from real users.

It’s not lab data emulated by a computer somewhere in a data centre.

The Chrome User Experience Report provides user experience metrics

The “real data from the real users” is based on statistics collected by Google via its web browser Chrome.

Google collect the data only for opt-in users in the Chrome User Experience Report or CRUX.

Each time someone visits a website, data are sent to Google about the performance and other metrics of the webpage.

Also, if your website is not generating enough traffic or if your audience is not using Chrome for some reason, you might not have any information collected about the Core Web Vitals.

The CRUX data are public and various tools testing the Core Web Vitals, including the one from Google, leverage this data to offer a report.

Core Web Vitals data aggregated over 28 days

Keep in mind that the data aggregated by Google in the CRUX report are not instantly available.

It is not real-time data.

There is a time span of 28 days. If you make some changes to your website, the report will only show you the impact 28 days later.

Google has no plan for the moment to speed up the process.

The impact of Core Web Vitals on SEO

Google does use Core Web Vitals in its search algorithm.

These signals have been a ranking factor since May 2021 and apply to mobile Search. The Core Web Vitals are also a Desktop Search ranking factor since February 2022.

Having a fast loading website and a great user experience will always be a plus for your website users.

But will the Core Web Vitals dramatically changes the SEO Game?

We can develop some aspects of their impact on search engine optimization.

Only 30% of websites passing the Core Web Vitals

In a study from February 2022, Ahref indicates that nearly 33% of websites are passing the Core Web Vitals threshold.

The graphic below shows as well an increase of 10% since the Core Web Vitals are part of the SEO game in 2021.

We could also read the graphic the other way and say that: 70% of websites do NOT pass the Core Web Vitals.

I assume two reasons why websites do not pass the Core Web Vitals (or why website owners do not invest in passing the Core Web Vitals:

Reason 1: It is hard to pass the threashold, especially if your audience is comming from a country with bad internet connection
Reason 2: Website owners invest their time and ressources on other aspect of SEO such as content, building link and generating brand awareness that could be more impactful for their website performance.

70% of websites do NOT pass the Core Web Vitals.

A tied factor

Google will never tell its secret recipe and reveal the exact weight of a ranking factor. We could have learned from various sources at Google that the Core Web Vitals are more tie-breaker ranking signals.

What does this mean?

If two pages are more or less equal in terms of ranking, the most performant page will get an advantage. So the page with the best Core Web Vitals will win over the other. In theory.

So we could consider that Core Web Vitals are not the most critical ranking factor, and other factors that make your page or website a good experience for a user is when you offer great content.

The most relevant content will always be the first

Google indicates that the pages with the best information, even if the experience of the pages is lower, will have a better ranking.

The quality of the content (and the number of backlinks) will for have priority over the page performance.

John Mueller himself said, “relevance is still by far much more important.” (Source)

However, as said previously, in cases where pages may be similar in terms of relevance, the pages with the best experience will rank first.

The most relevant content will always be the first

In our world of information in constant competition and copycat content, the user experience could be the differentiating factor in the future.

More Business Impact than SEO Impact

There is not a lot of study showing drastic ranking changes of websites with improved Core Web Vitals.

It is hard to isolate the metrics and identify that they impact ranking changes on the SERP, as other factors are always involved in ranking.

However, on-site impact and conversation rates can be better measured, and some studies show an increase in sales or conversion once the Core Web Vitals metrics are improved.

For instance, thanks to an A/B Testing and an improved LCP, Vodafone achieved 8% more sales. (Find more details here and other case studies.)

It seems evident that a better page experience and a fast-loading website generate more sales than a slow website.

Go Further with the Core Web Vitals

Tools Measuring Core Web Vitals: Now that you understand these new performance metrics, you can check out the tools to measure the Core Web Vitals.

Step by Step optimization with Google Search Console: The Google Search Console (GSC) gives all the information you need about the Core Web Vitals for your website. You must understand to take advantage of this information.

Tips to improve Core Web Vitals: Start optimizing your website by following best practices.