Google has added mobile-first indexing information including if you are on mobile-first indexing, if so, when you switched over and so on, to the toolsets and reporting within Google Search Console. This was announced on Twitter and aims at helping webmasters "understand how Google is crawling your website," Google said.
First you can access to see what crawler is currently indexing your site by going to Google Search Console and clicking on settings. There you can see if you are on desktop or smartphone crawler and if you are on smartphone, Google will show the date you switched over.
Here is a screen shot of a site on desktop crawling/indexing:
Here is a screen shot of a site on smartphone crawling/indexing and note it says the date it switched over:
Then in some of the reporting and tools, it will show at the top right which crawler the report is using - annotation number one. And then also if within the chart period the crawler changed, it will show the annotation of when it changed, see annotation number two:
This is obviously super useful to all of us!
Forum discussion at Twitter.
