In a Google webmaster hangout, Google’s John Mueller said that Google will release the mobile-first index later this year:
I don’t have any dates [but] it is not going to be years. I would guess, later this year sometime. But we will inform people as we get closer, as we have a date, so there is sufficient time for people to resolve issues that they might need to resolve.
We will try to also inform sites where we recognize issues. Such as maybe your mobile version doesn’t have all the same content and markup that your desktop version has. And we will try to let you know of that through Search Console as well. So that you are kind of aware of these issues.
I don’t know about Q1 but it is differently not like next week where we will be switching [the mobile first index] on.”
You can view the video here:
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