It was announced at PubCon (a webmaster conference) by Gary Illyes that Google is planning to roll more sites into the mobile-first index over the next several weeks.

The following tweet was posted by Marie Haynes, who was in the crowd, on Twitter:

Jesse McDonald, who was also in the crowd, posted this on Twitter as well:

Google’s mobile-first index is their attempt at looking at the web and indexing and ranking the web from a mobile-first perspective.  So if you have a mobile-friendly website, rather than indexing the desktop version, Google will index that website’s mobile version first.

There is a large FAQ for everything we know about the Google mobile-first index on Search Engine Land.

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