Mobile First Index

Google’s Mobile First Index is a change in the search engine’s indexing approach, in which the mobile version of a website becomes the primary version for indexing and ranking in search results, in the wake of the fact that most users access Google Search via a mobile device.

As of July 1, 2019, indexing prioritizing mobile content is enabled by default for all new websites discovered by Googlebot.

With the Mobile First Index, Google predominantly launches Googlebot in smartphone agent mode to determine a site’s relevance and usefulness to the user. However, this does not mean that there is a separate index for mobile devices and desktop sites-Google Search continues to use only one Index.