Is There A Difference Between Core Web Vitals And PageSpeed Insights?

Many SEOs and webmasters have asked the question – “Why are page speed results on Google Search Console’s Core Web Vitals different to PageSpeed Insights?” Google’s John Mueller explains the difference in the scores:

“I think maybe first of all, to get the obvious answer out the door, where is no correct number when it comes to speed, when it comes to understanding how your website is performing for your users.

In PageSpeed Insights, by default, I believe we show a single number that kind of is a score from 0 to 100, something like that, which is based on a number of assumptions, where we assume that different things are a little bit faster or slower for users.

And based on that we calculate a score.

In Search Console we have the Core Web Vitals information which is based on three numbers for speed, responsiveness and interactivity.

And these numbers are slightly different, of course, because it’s three numbers not just one number.”

“But also there’s a big difference in the way that these numbers are determined.

Namely there’s a difference between so-called field data and the lab data.

Field data is what users have actually seen when they go to your website. And this is what we use in Search Console.

That’s what we use for search as well.

Whereas lab data is kind of a theoretical view of your website, like where our systems have certain assumptions where they think, well the average user is probably like this, using this kind of device and with this kind of a connection perhaps.

And based on those assumptions, we will estimate what those numbers might be for an average user.

And obviously you can imagine those estimations will never be a hundred percent correct.”

“And similarly, the data that users have seen, that will change over time as well, where some users might have a really fast connection or a fast device and everything goes really fast on their website, or when they visit your website.

And others might not have that.

And because of that, this variation can always result in different numbers.

Our recommendation is generally to use the field data, the data you would see in Search Console, as a way of understanding what is kind of the current situation for a website.

And then to use the lab data, namely the individual tests that you can run directly yourself, to optimize your website and try to improve things.

And when you are pretty happy with the lab data that you’re getting with your new version of your website, then over time you can collect the field data, which happens automatically and double-check that users actually see it as being faster or more responsive as well.

So in short, again, there is no absolutely correct number when it comes to any of these metrics.

There is no kind of like absolutely correct answer where you’d say, this is what it should actually be.

But rather, there’s different assumptions and different ways of collecting data and each of these are subtly different.

In summary:

  • The Google Search Console tool provides granular snapshots of real-world site performance.
  • PageSpeed Insights is a diagnostic tool, to identify problems and offer suggestions for improvement.