Google controls the online world. The company’s global search market penetration is nearly 60 percent, so when the search giant speaks it’s natural that marketers listen—especially when Google announces sweeping changes to its mobile SEO rankings system as it just did. Beginning April 21, Google will start ranking websites optimized for mobile users, partly via responsive web design, higher than sites it deems as unfriendly to mobile users.

A majority of digital media consumption and local web searches occurs via smartphones and tablets. Between August 2013 and August 2014, mobile web usage grew by 67 percent. In a recent blog post, Google stated that as more people use mobile devices to access the Internet, its algorithms have to adapt to upcoming usage patterns to ensure quality control for all of its users.

That’s why Google is expanding on its previous changes where it ensured a website is configured properly and viewable on modern devices. The company’s SEO team also made it easier for users to find mobile-friendly web pages, and they introduced App Indexing to snag any useful content from apps during web searches.

Google’s expansion of its mobile-friendly ranking system is going to have significant changes for any websites that fails to adapt. Companies without mobile or responsive websites are going to be slammed with up to a 20 percent or even a 30 percent decrease in their web traffic.

“This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results,” Google stated in its blog. “Consequently, users will find it easier to get relevant, high quality search results that are optimized for their devices.”

Google’s web crawler determines mobile-friendliness on a page-by-page basis and considers a website mobile-friendly if and when that site: avoids software that is not common on mobile devices, like Flash, uses text that is readable without zooming, sizes content to the screen so consumers do not have to scroll horizontally or zoom, and places links far enough apart so that the correct one can be easily tapped.

These algorithm changes make the need for companies to have a responsive site design absolutely necessary, rather than a nice commodity. While Google isn’t initializing a penalty on websites that fail to be mobile-friendly, ones that do will certainly receive a ranking boost. And businesses that fail to adapt to this change will rank far below those that do adapt. Although a responsive design site won’t improve a website’s ranking, it should prevent any major drops in ranking power.

In the video below Google’s Matt Cutts explains some of the benefits of responsive design over unique mobile pages. Learn more about optimizing your website for mobile with responsive design to increase visibility and engagement in our education center.