This week, Google rolled out its “mobile-friendly” label to its mobile search results. To quickly test your site to see if it meets Google’s criteria for mobile-friendly, just stick your URL here:
Did your site pass? Yea! If not, there are a few simple things you can do. Google gives all sorts of handy tips about how to make your site mobile-friendly. One solution is to switch your site to an open-source CMS that uses a responsive template. But that’s not absolutely necessary.
You can read more in their developers blog