Google announced this morning that starting on July 1, 2019 they will begin to index new web sites, not yet discovered by Google, using mobile-first indexing by default. Old web sites not yet in mobile-first indexing still won't be switched until they are ready but brand new sites, not yet indexed by Google, will come right out of the gate as using mobile-first indexing.
Google said that their "analysis has shown that new websites are generally ready for this method of crawling." That being said, "mobile-first indexing will be enabled by default for all new, previously unknown to Google Search, websites starting July 1, 2019," Google added. If you launch a web site that doesn't work on mobile - then you will be out of luck and have issues.
Google won't send notifications to these new sites that they are being indexed using mobile-first indexing because that will be the default behavior. So don't expect to be notified when you launch a new site after July 1st that your site is using mobile-first indexing.
With older sites that have not yet moved, which is less than 50% of the sites Google said some time ago, those will continue to be using desktop-first indexing until they are ready. Google wrote "For older websites, we'll continue monitoring and evaluating pages for their readiness for mobile first indexing." And when those sites are moved over, Google said they "will notify them through Search Console once they're seen as being ready." Just note, that last half will be hard for Google to move.
Google is highly recommending that new sites go with a responsive design. Google wrote "While we continue to support responsive web design, dynamic serving, and separate mobile URLs for mobile websites, we recommend responsive web design for new websites. Because of issues and confusion we've seen from separate mobile URLs over the years, both from search engines and users, we recommend using a single URL for both desktop and mobile websites."
Again, mobile-first indexing is not a ranking factor - it is just how Google indexes. Being mobile-friendly is a ranking factor and those are two different things.
Mobile-first indexing isn't a ranking factor -- it's just how we crawl & index the content.
— 🍌 John 🍌 (@JohnMu) May 28, 2019
And Google does not determine a site is ready for mobile-first indexing by traffic. It is more about if the site is technically ready:
Mobile-first indexing doesn't go by traffic proportions.
— Martin Splitt @ 🇨🇭🏡 (@g33konaut) May 28, 2019
Gary Illyes from Google said Google put a ton of testing into this and they seem confident with the July 1st date for this change:
This has been in the works for so long, so many tests and experiments, I'm super happy to see this go live!
— Gary "鯨理" Illyes (@methode) May 28, 2019
Official Google Webmaster Central Blog: Mobile-First Indexing by default for new domains https://t.co/jXezJtitVw
Forum discussion at Twitter.
