Q: How do I know if my site is mobile friendly?
A: There are a few ways but the only way to know if your site is already indexed by Google as mobile friendly is to see if your site has the mobile friendly label in the mobile search results. Using the mobile friendly testing tool will show if you pass the test, but Google may still need some time to update their index to pick up on the fact that your web pages are mobile friendly. You can also the mobile usability reports within Google Webmaster Tools, but those can be fairly delayed.
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Google AMP and Facebook's Instant Articles info - late Jan 2016 - Jan 26, 2016
Have tablets jumped the shark? - Mar 19, 2014
Decline of the Mobile Web - April 2014 - Apr 10, 2014