Google will be bringing its upcoming mobile-first indexing for search results to sites that have prepared for the change before any others, according to a recent hangout with Googler John Mueller. During the Hangout, Mueller talked over the upcoming change in some detail, announcing that not only would some sites be indexed before others, but that webmasters could go uninformed about their sites having been indexed, making search engine optimization a bit harder than it would otherwise be. Though Mueller explained at length the rollout of mobile-first indexing, he was tight-lipped on when exactly the change would take place or how webmasters could tell that their sites have been indexed or where they ranked, aside from extensive searching of their usual keywords.
While this means that webmasters who do the work of preparing their websites for the rollout of Google's new indexing method will get a boost in traffic for a little while among mobile users, the indexing will come to all sites with mobile pages eventually. At that point, the advantage will lie with those whose sites please Google's algorithm for search, just as it has always been. The only difference at that point, of course, will be that sites with a mobile component will appear before non-mobile friendly sites in the search rankings for anybody searching from a mobile device.
Google began experimenting with mobile-first indexing back in 2016, but will not begin to roll it out to the public until at least 2018, according to previous word from the company on that subject. While the point of mobile-first indexing is to help mobile users find content suited to their devices, sites without a mobile component will not be wiped off of the map entirely by this change. Instead, sites with a mobile-friendly or dynamic version will get a fixed ranking boost, and will be ranked on both their desktop and mobile site. As with search ranking before the change, content, how well-made the site is, and relevance to the search at hand will all factor into where a site gets placed in the rankings. While this theoretically means that mobile users will always see mobile results first, that may not always be the case when it comes to extremely niche searches, or searches for specific sites that don't have a mobile component. Google started the march toward massive changes to its searching service by optimizing the indexing of "modern" sites back in 2014.