This is the part where those word vectors and are put to good use. This is also the part where most likely comes into play. Hummingbird too (I think - not that it matters.) Ranking is the part that obsesses us the most. This is where they rank the results based on the number of factors we are discussing today. Much of this likely happens during the recovery phase. However, some factors (like penalties, speed, and even mobile compatibility) are likely to occur after recovery. At least, that's how I would code it - but I'm not as smart of an engineer as some people at Google. Alright, what does any of this have to do with the Mobile First Index? I'm getting there, but the WordPress plugin says I need a few hundred more words, so be patient. (Just kidding, I swear this is helpful.) So what is Mobile First indexing?
Currently, Google only has one index based on the desktop site. It creates signals based on Googlebot with desktop user agent. Google hair masking service then crawls with its mobile Googlebot to collect mobile and other signals, but they don't create a new index based on the mobile site. Currently, when a user searches Google (desktop or mobile), the retrieval part of the algorithm looks at the desktop index created by the Googlebot desktop crawler. It finds relevant results based on the desktop index, then ranks them based on the desktop index and even shows the searcher a snippet based on the desktop index. The Ranker then reviews the mobile signals collected by the mobile crawler and adjusts the ranking accordingly. This caused some problems.
There are way too many cases where a user sees something in a snippet, clicks on the results, gets redirected to the site's mobile homepage (which probably spawns an app store or newsletter popup ), then realizes that the content he saw in the search snippet isn't available on the mobile-clean version of the site. It's a bad user experience, but it's pretty much the norm on too many sites. With this new change, Google is looking to stop that. The general theory (I'm not talking about Google or Gary) is that if the content isn't important enough to be on your mobile site, then maybe you're not the most relevant result or the most relevant to this content. Ok… what does this mean? Most of the conversations and blog posts I see lately are all about ranking. While it's true that indexing can affect rankings, that shouldn't be our primary concern.