This may go down in history as the week the mobile web became the web.

On Monday, Google began indexing and ranking pages on its search engine based on the mobile versions of websites rather than the desktop ones, the company announced. The change may seem minor, but it underscores how Google views and presents the web to the world—as mobile first.

The search giant, which fields much of the world’s search queries, said back in 2015 that mobile searches had overtaken desktop in parts of the world. The trend continued, and a year and half ago Google started experimenting with mobile-first indexing to help its majority-mobile users find what they’re looking for. Mobile and desktop versions of pages can vary widely, which can be confusing for users on mobile who expect one thing from their search results and encounter another.

Mobile-friendliness has long been played into how Google ranks webpages in its search engines, as TechCrunch pointed out. Pages that are mobile-friendly rank higher in mobile searches than those that aren’t. And the speed in which a page loads will factor into where it ranks in mobile search results starting in July.

Google has a single index that serves search results on mobile and desktop, the company said, so desktop search results will be fed by the mobile-first index, too. Webpages that only have desktop versions will continue to be included in the Google’s index based on their desktop sites. It added that content gathered through mobile-first indexing will have no ranking advantage over desktop or mobile content that’s not gathered in this way yet.