As you know, Google said they have begun the mobile-first indexing rollout a couple weeks ago and SEOs and webmasters are a bit nervous about it. But Google keeps telling folks to relax and not worry too much about it.
Google's John Mueller said on Twitter yesterday that before Google moves a site from desktop-first indexing to mobile-first indexing, they do look to see the links on the desktop version and compare that to the mobile version. If those links in the content and source code of the pages are not equivalent enough, I suspect the site will not yet move over to mobile-first indexing.
John said "We do check for things like links before switching sites over, so I'm not too worried." "If your site has insufficient links on mobile, you should be fixing that regardless," he added.
We do check for things like links before switching sites over, so I'm not too worried. If your site has insufficient links on mobile, you should be fixing that regardless (I hate it when sites don't provide the normal functionality everywhere).
— John ☆.o(≧▽≦)o.☆ (@JohnMu) April 10, 2018
The plan is not to switch sites over until they're ready, but fixing issues is always good.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) April 10, 2018
FYI - I have yet to see a site that has moved over to the mobile-first indexing process yet. I am watching like a hawk and I see zero cases of anyone reporting their site has moved over. If you know of any sites, do let me know.
In short, make sure your desktop and mobile pages are equivalent, this is something Google has been saying repeatedly for a while.
Forum discussion at Twitter.