Since the inception of its search engine nearly 20 years ago, Google has used the desktop version of websites to determine relevance and other ranking signals in order to populate its search index. Back in 1997, internet content consumption primarily took place on desktop and laptop computers, while mobile devices were still at least another decade away before reaching mainstream popularity.
With the realization that most people search on Google using mobile devices, the company has begun experimentation with switching to a mobile-first indexing methodology. This will be of particular interest to webmasters, depending upon the configuration of the websites under their management.
Google acknowledged the significance of the undertaking, and said:
"We understand this is an important shift in our indexing and it’s one we take seriously. We’ll continue to carefully experiment over the coming months on a small scale and we’ll ramp up this change when we’re confident that we have a great user experience."
While mobile-responsive and dynamic serving sites should not require any changes, Google has made several suggestions for sites that maintain separate markup for mobile and desktop devices. Otherwise, sites optimized only for desktop consumption will continue to be indexed as they are now.
For websites that do not currently offer a mobile-optimized experience, the news may inspire webmasters to quickly build and deploy a solution. However, Google recommended a more careful approach, as "a functional desktop-oriented site can be better than a broken or incomplete mobile version of the site."