Google tries to enhance mobile website owners understanding of what their site delivers into the mobile experience.
Google warns site owners their site is not mobile-friendly in mobile search results
A month before the Google mobile-friendly algorithm boost, they start issuing new warnings to site owners.
Google is now issuing a new type of warning to site owners if their site is not mobile-friendly. The new warnings show directly in the mobile search results, but only to the site owner, when Google knows that the searcher is the owner of the site.
Jennifer Slegg has an old site that is not mobile-friendly, and she reported that when she views the site in the mobile search results, it says to her in the snippet, “Your page is not mobile-friendly.” That message is a hyperlink to a Google help page about mobile-friendly.
Here is what Jenn sees as the site owner of a non-mobile-friendly website:
Here is what anyone else would see for this site — no warning:
This new warning comes a month prior to Google boosting the mobile-friendly algorithm.
John Mueller of Google confirmed this is an experiment they are trying out to see if it helps boost mobile-friendliness.