Google has announced that as of April 21st they will be using mobile-friendliness as a ranking signal throughout mobile search results. The new algorithm update may take up to a week to fully roll out. This change will affect worldwide mobile search results in all languages, and Google says it will have a “significant” impact. Google is working towards delivering primarily mobile-friendly sites in mobile search.
To ensure that your site still appears in Google’s mobile search results after April 21st, run your site through the mobile-friendly testing tool. If your site passes, you shouldn’t have anything to worry about. If your site doesn’t pass, then the tool will recommend the improvements you need to make.
Mobile-friendliness is not ranked on a scale – your site is either mobile-friendly or it isn’t. Your website has to fully pass Google’s criteria in order to be considered mobile-friendly.