Google updated the Core Web Vitals report in Google Search Console on March 27, 2023. The update may have resulted in a change in the number of URLs in your Core Web Vitals report, the search company wrote.

Google wrote, “You may see a change in the number of URLs in your Core Web Vitals report. This is because more URLs are now being reported on due to a new origin group that contains data for URLs that previously fell below the data threshold.”

You should see a little marker notifying you of this update in the report, here is what it looks like:

Here is more about URL Groups from the Google help document:

Note, I don’t think Core Web Vitals are that vital to SEO, so I wouldn’t get bogged down in these reports for SEO or ranking reasons.

Forum discussion at Twitter.