It’s still being called and ‘experiment,’ but it’s actually the beginning of Google’s planned shift to looking primarily at mobile content, rather than desktop, when deciding how to rank results.

What is Mobile-First indexing? Google will primarily look at the mobile version of your website for its ranking signals and fall back on the desktop version when there is no mobile version.

We expected this was coming and even heard about it over a year ago, but this is the first time Google has posted details about the mobile-first index on their own blog.

While more of Google searches are now mobile, it’s index is still currently desktop. With this change, Google will primarily index mobile content and use that to decide how to rank its results, regardless of whether you’re on desktop or mobile. There will no longer be any type of “mobile-friendly” adjustment done just for mobile users.

Read More: Google begins mobile-first indexing, using mobile content for all search rankings