There are now more searches being done through mobile devices than desktop PCs, prompting the move to mobile first indexing. In the following years, Google started giving a search ranking boost to sites with mobile versions, but only in Google Search Mobile, leaving its Desktop Search unaltered.
To fix this issue, the company has begun experimenting with a "mobile-first" approach to indexing web pages.
Google also said "site owners will see significantly increased crawl rate from the Smartphone Googlebot".
There's been some confusion in the past few weeks about the possibility of there being two indexes, with mobile being the primary one, but I haven't been able to find any official word on this happening.
The company did not specify when the rollout of the mobile-first index would complete.
According to Google, there will be only one index for search results that means a mobile-first index will be separated from its main index.
In its press release, Google said that while the change will not affect rankings, developers and businesses are encouraged to make their websites more mobile-friendly.
To check whether a page is mobile-friendly, you can check out Google mobile-friendliness test here.
Today's announcement will have a huge impact on search engine rankings, as mobile content will now actually matter. And it wouldn't be a good user experience for Google to exclude or devalue those searchers because the site is not mobile friendly, when the majority of the searchers still want to go to the site. We do evaluate all content in our index - whether it is desktop or mobile - to determine how mobile-friendly it is.