After a year and a half of testing, Google is rolling out its mobile-first indexing of the web. According to TechCrunch, Google first detailed its plan in 2016, aiming to “change the way its search index operates, explaining how its algorithms would eventually be shifted to use the mobile version of a website’s content to index its pages, as well as to understand its structured data and to show snippets from the site in the Google search results.” The move caters to Google Search users, the majority of whom search via mobile devices.

As TechCrunch reports, Google started actually transitioning to the use mobile-first indexing in December 2017, kicking things off with a small number of sites, which they declined to name. According to a company blog post, the goal of mobile-first indexing is to use the mobile version of a web page “for indexing and ranking, to better help our — primarily mobile — users find what they’re looking for.”

Google explains that it won’t have two separate indexes — one for mobile and another for desktop. Rather, “it will start to look to the mobile web pages to index the web, not the desktop version,” according to TechCrunch. However, the company isn’t shifting all sites to mobile-first right away. Instead, it will roll out over time (no official time frame was provided), starting with sites “already following the best practices for mobile-first indexing.”

Mobile-friendliness is only going to get more important for companies and individuals on the web as time goes on. Google prioritizes mobile in a few ways, including boosting “the rank of mobile-friendly webpages on mobile search results” and “adding a signal that uses page speed to help determine a page’s mobile search ranking.”

The company claims the new mobile-first indexing won’t directly impact content rank, and that companies who only have desktop content as of now will continue to be represented in the index.

However, “it does note that having a site’s mobile-friendly content indexed in this new fashion will likely help the site ‘perform better’ in mobile search results. And it will favor the mobile version of the webpage over its own fast-loading AMP pages,” reports TechCrunch. (AMP is Google’s open-source Accelerated Mobile Pages publishing tech.)