Google today said that over time it will switch to using the mobile versions of websites, instead of desktop versions, in order to rank them for search results, thus making its search index more mobile-first.

So far, the company has started experimenting; the shift could take some time.

“Although our search index will continue to be a single index of websites and apps, our algorithms will eventually primarily use the mobile version of a site’s content to rank pages from that site, to understand structured data, and to show snippets from those pages in our results,” Google product manager Doantam Phan wrote in a blog post. “Of course, while our index will be built from mobile documents, we’re going to continue to build a great search experience for all users, whether they come from mobile or desktop devices.”

This comes after Google has taken several steps to improve the experience of search on mobile devices. In November 2014 Google started marking pages as mobile-friendly in mobile web search results. In February 2015, Google said that within two months it would start using mobile-friendly as a ranking signal (aka Mobilegeddon). Most recently, in March, Google said that in May it would start ranking mobile-friendly sites even higher.

This is going further because it goes across the board, on mobile and desktop.

“We understand this is an important shift in our indexing and it’s one we take seriously,” Phan wrote. “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.”