Google Search begins mobile-first indexing for all new websites starting on July 2019. The search engine has previously taken into account the quality and availability of the mobile version of the website, but from July this will be a priority.
This is not surprising since the mobile-first indexing initiative has come a long way since Google first announced its plans back in 2016.
The new system means that the position of the pages in the search will depend on their mobile version, and not for desktop computers one, as it was before.
Mobile-first indexing will be enabled by default for all new, previously unknown to Google Search, websites starting July 1, 2019