Why do web pages drop out of Search Console reports?

• We're having a problem with some of our web pages showing up and then dropping out of Search Console reports.

  Especially in regards to the Core Web Vitals report, we're seeing a steady decline in the number of pages reported from month to month.

  Do you have any idea why our pages are dropping out of that report?

Answer:

It's actually a matter of how Search Console reports on web pages. Rather than attempt to include every page in the report, they use a sample of the URLs from your site. The number of pages they use to sample your site can vary from month to month in exactly the way that you're reporting.

Google's John Mueller recently addressed this issue in an office hours segment where he said,

...it's something where having fewer URLs in these reports doesn't mean that the other URLs are bad or problematic. It's just we didn't check them. So especially for the aggregate reports, which is for the Core Web Vitals to some extent, the AMP report, the Structured Data report, mobile friendliness ... for those reports we only take a look at a sample ... and that sample can change over time.

He goes on to say they might look at 200 URLs in one month and then in the next they'll look at maybe 100 URLs or something like that. It doesn't mean that anything bad is happening, it's just that Google is looking at a smaller sample of pages from your site.

So, instead of stressing out about the changing sample size you should focus on what is actually being reported – specifically the relationship between the bad pages that are reported and the good ones.

If you see that all of the URLs in the report are without errors, then you're good to go. Nothing to worry about. ...