Google says mobile-first indexing is now used for over half the web pages in its search results

Google announced today it’s now using mobile-first indexing for over half the web pages shown in its search results globally – a significant milestone in Google’s move to favor mobile sites over desktop sites in its search results.

The plans for the project have been in the works for years.

The company had first detailed its efforts around mobile-first indexing back in 2016, where it explained the impacts to how its search index operates. It said it would shift over to using the mobile version of a website’s content to index its pages, as well as to understand its structured data and show snippets from the site in Google’s search results.

Its reasoning behind the change is simple: most people today search Google from a mobile device, not a desktop computer. But Google’s ranking systems for the web were originally built for the desktop era. They still typically look at the desktop version of the page’s content to determine its relevance to the user.

This, obviously, causes problems when the desktop site and the mobile site are not in sync.

Before responsive web design became more commonplace, many site owners built a separate, simpler and sometimes less informative version of their site for their mobile web visitors. These users may have been guided to the site because of Google Search. But once there, they couldn’t find what they were looking for because it was only available on the desktop version of the web page.

In December 2017, Google said it had begun to transition a small handful of sites to mobile-first indexing.

Earlier this year, Google announced it had begun to officially roll out its “mobile-first” indexing of the web, following a year and a half of testing and experimentation. At the time, it said it would first move over the sites already following the best practices for mobile-first indexing. It also noted it would favor the site’s own mobile version of its webpage over Google’s fast-loading AMP pages.

Sites who are shifted are notified through a message in Search Console and then see increased visits from the smartphone version of Googlebot, which crawls the mobile version of their site. Site owners can also check their server logs, where they can track the increased requests from Googlebot Smartphone.

Google additionally offers a URL inspection tool, which site owners can use to check how a URL from their site – like the homepage – was last crawled and indexed.

Google today notes that sites that don’t use responsive web design are seeing two common problems when Google tries to move them over to mobile-first indexing.

Some don’t use structured data on their mobile sites, even though they use it on the desktop. This is important because it helps Google to understand the website’s content and allows it to highlight pages’ content in its search results, through its “fancier” features like rich results, Knowledge Graph results, enhanced search results, carousels and more – basically any time you see more engaging search results that offer more than just a list of blue links.

The company also said that some mobile sites were missing alt-text for images, which makes it harder for Google to understand the images’ content.

At the time of the initial wave of sites being shifted over, Google had said that the mobile-friendly index wouldn’t directly impact how content is ranked, but it did say that a site’s mobile-friendly content will help it “perform better” in mobile search results. Mobile-friendliness has also long been one of many factors in determining how a site is ranked, but it’s not the only one.

Google didn’t say what it will do to sites that are never properly updated for the mobile web, but it seems that – at some point – their ranking could be impacted.