John Mueller a Webmaster Trends Analyst at Google has confirmed that mobile-first only relates to how a website is indexed and does not affect how a site ranks.
The question was asked on Twitter:-
Hi John, would that [mobile first] mean that a website that has been moved would have an upper-hand on a website that hasn’t been moved?
John Mueller replied:-
No, it doesn’t change ranking, it’s just how it’s indexed.
It was a follow-on question regarding a website which hadn’t been moved to mobile-index. John Mueller’s response was not all sites have been moved yet.
You can see the live tweet here: https://twitter.com/JohnMu/status/1068561779490504704
Websites on mobile first index do not have an upperhand
Websites which have moved to the mobile first index do not have an upperhand on websites which are still on the original desktop index. Of course if the website is not mobile friendly you could run into technical issues. For instance if the content doesn’t fit within the page frame it may not be indexed.
Have all website been moved to mobile first yet?
Again, the short answer is no, not all websites have been moved although it would appear the majority are now on the mobile first index.
Will mobile first impact a website’s ranking?
John Mueller confirmed it doesn’t change ranking only how the site is indexed.
Disclaimer: We cannot guarantee the accuracy of this information. It is your responsibility to interpret the information we have provided and obtain professional help for your specific situation.