In a recent SEO Office-hours session, John Mueller answered a query concerning why the core web vitals scores keep changing even when the web pages themselves haven’t changed.

What exactly are the Core Web Vitals?

Three indicators that rate a user’s experience loading a webpage are known as Core Web Vitals. These metrics rate the speed with which page content loads, the speed with which a browser loading a webpage can respond to a user’s input, and the stability with which the content loads in the browser. These three indicators will be combined with Mobile Friendliness, Safe Browsing, HTTPS, and Intrusive Interstitials to form the “Page Experience Signal,” according to Google.

The question asked by john Mueller was,

“When does the core web vitals give steady and correct information?

It keeps changing without changing any data on the website.”

John Mueller answered:

“So, I think this is probably a side effect of how the core web vitals and the page experience update is processed.

And that’s something where I would try to look up those details to understand a little bit more about how the field data, …the data that users actually see, kind of plays a role in this.

And that is something where if users from a wide variety of backgrounds and different locations and different device types access your pages, you will probably see some fluctuations over time there as well.”

 Network latency 

As John Mueller pointed out, there are other aspects that affect the core web vitals scores, many of which are outside our control.

A fast server and a quick website are only one component of achieving a high core web vitals score, and it’s the only one that the SEO or site publisher can manage.

Even if a website is maintained on a fast dedicated server, network congestion, a visitor’s old cell phone, and poor mobile data connectivity can all have a major impact on the core web vital performance.

Web.dev says:

“The most important thing to understand about field data is that it is not just one number, it’s a distribution of numbers. That is, for some people who visit your site, it may load very quickly, while for others it may load very slowly.

The field data for your site is the complete set of all performance data collected from your users.

As an example, CrUX reports show a distribution of performance metrics from real Chrome users over a 28-day period. If you look at almost any CrUX report you can see that some users who visit a site might have a very good experience while others might have a very poor experience.”

Source – Search engine journal