Since April 21, 2015, Google has been using mobile-friendliness as a significant ranking factor.
This means that sites that are not properly optimized for mobile devices will achieve lower rankings in mobile search results. Given that we are now in the mobile age, this is pretty big deal.
If you noticed a drop in your search rankings, this is a clue that you site is probably not properly optimized for mobile. However, if you want to be completely sure, there are online tests you can use to determine the mobile-friendliness of your site.
Google’s mobile-friendly test is the most accurate tool to use. One thing to remember though is that this tool checks via web page, not domain. This means that even if one page “passes”, it does not mean every page on your site will. Google provides guidance on how to fix any mobile issues.
The speed a page loads is also a critical ranking factor. Google’s PageSpead insights tool goes into greater detailed instructions on how to speed up your page. The tool provides you with two separate scores: one for speed and one for user-experience.
mobiReady is a tool that shows you how your page displays on various platforms — desktop, higher-tier phones, mid-tier phones, and low-tier phones. This tool provides your site with a score between 1 and 5. mobiReady also gives you a detailed listing of CSS elements and whether each is a pass, minor, or major fail.