Google has made it official. As of April 21, mobile-friendly will now be a ranking factor for web pages. The company says this will help users get relevant, high quality search results that are optimized for their devices.

We knew this was coming. As you remember, Google hinted of this change when it announced mobile-friendly labels a couple of months ago. They are now following through on that suggestion.

Don’t panic and rush into your SEO’s office and shout the sky is falling. Google will be ranking for mobile-friendly on a page-by-page basis in “real time”.   That likely means that once Google crawls the page again, it will pick up the mobile-friendly changes and the page will benefit from being considered mobile-friendly now. The catch is that it may take some time for Google to re crawl your page, especially if it is one that doesn’t change on a regular basis. If this is the case with your pages, you may want to start sooner rather than later.

The fact it is done on a page-by-page basis rather than the entire website is significant. This means that if you have a 15 page website and 8 of the pages are mobile-friendly and the rest are not yet, then the 8 mobile-friendly pages will benefit. You may have sub-sections of your website that are more difficult to make mobile-friendly. At this point these will not drag down the entire site if they are not mobile-friendly by April 21.

However, from a holistic search engine optimization standpoint, you want to make your entire website user friendly. Being mobile-friendly is important as the world is going mobile and Google just gave you a huge incentive to do so.