Mobile-First... losing pages from index, but no traffic losses

[vegasrick]

I don't seem to be losing traffic, but week by week I've been losing indexed pages (in search console) since mobile-first was activated for the site.

I have very few mobile usability issues.

I see a ton of pages under "Crawled - currently not indexed"

Not sure if this is just a process that everyone is going through, the site is being re-indexed, or something else is wrong.

[wavingdave]

We're also seeing oddness in GSC, with a load of pages "Crawled - currently not indexed" too.

There was a 4-month gap between our massive Mobile Googlebot surge and us getting the MFI message, and in that time the number of "Valid" URLs (Coverage report) dropped about 25%. A couple of days after getting the MFI message (2 weeks ago), the Valid URLs total jumped up about 15% and has stayed there.

We have pruned a fair amount of dead content in that time, which might explain some of that, but...

Oddly, under "Mobile Usability" we have zero errors but the number of reported Valid pages (which itself is < 10% of the number of Valid URLs from the Coverage report) has dropped 50% in the 4 months, with a notable step down coinciding with the MFI message.

That makes no sense to me.

Has anyone else had vagaries in GSC, around Mobile indexing, that they've been able to drill down into and find a cause?

[magician]

I am also witnessing significant increase in "Crawled - currently not indexed" number. Not much change in traffic but significant portion of the site is now not being indexed. This is a new website.

One of the things which I have noticed in the report (new search console) for these non-indexed URLs is that google is able to find these URLs only in my sitemap but the 'Referring page' is 'None detected'. This report for all indexed URLs, highlights both the Sitemap and Referring Page.

All my non-indexed URLs are mostly 4th level links. It's possible google hasn't indexed 3rd level link as of now and hence not indexing 4th level links until it indexes the corresponding 3rd level links.

This is just a theory. In the past google used to index pages which is not even linked from any other page if submitted in sitemap. Probably some change in the algo there.