The talk for a long time now is that Google is placing more importance on mobile. Specifically, Google realizes that now over 50% of all web searches take place through mobile devices such as phones and tablets. In light of this fact, Google is returning results that favor mobile-optimized sites over non-mobile-optimized sites. These sites are known as “Responsive” meaning they automatically adapt to the resolution of the device displaying the site.
Not only is responsiveness a factor, but the speed with which it loads on mobile is as important. If your site loads slowly on a mobile platform, the search engines will downgrade your site in the rankings.
There are a couple of simple tools to test your site for both mobile-friendlyness and speed.
Google’s Mobile-Friendly tester. Enter your site’s URL and it will analyze your site for its ability to convert from desktop resolution to mobile resolution.
Google’s Page Insights. Enter your site’s URL to test if your site loads quickly enough. It will give you suggestions for what to fix based on level of importance.