GOOGLE MOBILE-FIRST INDEXING
According to Google “We continue to have one single index that we use for serving search results. We do not have a “mobile-first index” that’s separate from our main index. Historically, the desktop version was indexed, but increasingly, we will be using the mobile versions of content.”
Mobile-first indexing means that we’ll use the mobile version of the page for indexing and ranking, to better help our – primarily mobile – users find what they’re looking for.