I already said this when I wrote about the Google Page Experience Update but it is important to say again. If you have an AMP version and your site is on mobile-first indexing, which all sites should be by the end of this year, then Google’s Page Experience update will measure your AMP page, not your mobile or desktop page.

John Mueller of Google explained this clearly in a Google webmaster video from last week at the 43:50 mark.

In short, he said that Google will use the page experience scores based on what the searcher will see after they click over from Google to the web page. And if you have AMP, Google serves the AMP version to users on mobile. Thus the AMP page is what Google will use for measuring with core web vitals and such.

Here is the video embed at the start time:

Here is the transcript:

Google also said, generally, AMP pages do extremely well with the Page Experience scores. So stick with AMP?

Forum discussion at YouTube Community.