If your site is already “responsive” then you don’t need to make a panicked call to your web designer. You should not be negatively affected by this rollout.
But if you want to double check to see if your site is mobile-friendly – then just go here and type in the url.
John Mueller, Webmaster Trends Analyst at Google made the announcement on Twitter.
Please note that because this algorithm is a page-by-page ranking signal. You probably won’t notice any difference right away – it’s going to take time for the Google Gods to crawl through and index your entire site.
Which means that if you don’t have a mobile-friendly site you might want to get busy.