Google announced today that any new sites/domain names it indexes will be on a mobile-first basis. This means its Googlebot will crawl a mobile version of the site for indexing rather than a desktop version.
The search giant already does this for many websites, but for existing websites, it determines if they are ready for mobile first before using the mobile Googlebot. Not so with new websites; they must be ready to go out of the gate.
Of course, almost all new websites are mobile friendly and this is why Google is making the change.
In a blog post about the change, it noted that it still supports dynamic serving and mobile URLs but it advises against it. Instead, site owners should use responsive design. (Can we just get rid of .mobi already?)
I find Google’s desire for fully responsive sites to be somewhat in conflict with its AMP program, which uses separate URLs for fast-loading mobile pages.