Google has begun testing its mobile-first index, which 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.

Most of Google searches are mobile, but Google’s index is desktop

Google explained that it sees more mobile searches than desktop searches on a daily basis. But when Google looks to evaluate a page’s ranking in Google, it currently looks at the desktop version of the site — an issue we pointed out over a year ago. To fix this, Google will look at the content, links and structured data of the mobile version of your site if one is available.

Google wrote:

To make our results more useful, we’ve begun experiments to make our index mobile-first. 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. 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.

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. Effectively, if you’re not mobile-friendly, that will have an impact even on how you appear for desktop searchers

Google is testing this but hopes to roll it out to all

Google said it has started this experiment and will “continue to carefully experiment over the coming months on a small scale.” Google will “ramp up this change when we’re confident that we have a great user experience.”

No mobile site? Don’t worry

Those who do not have a mobile version of their website do not need to worry. Google will just use the desktop version to rank the site. Google wrote, “[I]f you only have a desktop site, we’ll continue to index your desktop site just fine, even if we’re using a mobile user agent to view your site.” This also means that if you have a responsive site, one that dynamically changes content depending on desktop or mobile device, there’s nothing special you need to do.

Of course, if you do not have a mobile site, you won’t benefit from the mobile-friendly ranking boost. But that is separate from this mobile index news.

How can you prepare?

Here are some recommendations Google is giving webmasters to prepare for the change:

If you have a responsive site or a dynamic serving site where the primary content and markup is equivalent across mobile and desktop, you shouldn’t have to change anything.

If you have a site configuration where the primary content and markup is different across mobile and desktop, you should consider making some changes to your site. Make sure to serve structured markup for both the desktop and mobile version. Sites can verify the equivalence of their structured markup across desktop and mobile by typing the URLs of both versions into the Structured Data Testing Tool and comparing the output. When adding structured data to a mobile site, avoid adding large amounts of markup that isn’t relevant to the specific information content of each document. Use the robots.txt testing tool to verify that your mobile version is accessible to Googlebot. Sites do not have to make changes to their canonical links; we’ll continue to use these links as guides to serve the appropriate results to a user searching on desktop or mobile.

If you are a site owner who has only verified your desktop site in Search Console, please add and verify your mobile version.

We will keep you posted

As we see changes to the Google results and index, we will report back to you with any issues. When this mobile-first index fully rolls out, we will let you all know.