Mobile-first indexing will be enabled by default for all new websites as of July 1, 2019.
This change applies to, in Google’s words, websites previously unknown to Google Search.
Google says the reason for this change is due to the fact that new websites are generally ready for mobile-first indexing out of the gate.
“Over the years since announcing mobile-first indexing – Google’s crawling of the web using a smartphone Googlebot – our analysis has shown that new websites are generally ready for this method of crawling.”
For older websites, it’s still business as usual. Google will monitor and evaluate pages for their readiness for mobile first indexing.
Google’s guidance on getting websites ready for mobile-first indexing remains the same:
“For existing websites we determine their readiness for mobile-first indexing based on parity of content (including text, images, videos, links), structured data, and other meta-data (for example, titles and descriptions, robots meta tags). We recommend double-checking these factors when a website is launched or significantly redesigned.”
Dynamic serving and separate URLs for mobile websites are still supported, however, Google ultimately recommends responsive web design for new sites.
Google will continue to send Search Console notifications to webmasters of older websites when they’re ready for the new method of indexing.
As mobile-first will be the default method of indexing for new sites after July 1, they will not be sent the same Search Console notifications as older sites.
Google will monitor and evaluate this change “carefully.”