Google has taken a great step ahead to rank websites based on the compatibility support for mobile users, usability factors and app indexing. This will affect only for users browsing google search on mobile devices. The algorithm for desktop/laptop users remains the same.
Google also said that mobile ranking factors will not only label your websites as mobile-friendly, but will also use that to determine if your website should rank higher in the search results.
This algorithmic change will have a “significant impact” in the mobile search results, impacting all languages worldwide. But this change is not done abruptly or as a earthquake. Google has been constantly providing hints to users from last October about “Mobile friendly” algorithm when it had launched mobile specific labels last year.
The android applications that are indexed by Google with the help of app indexing mechanism will begin to rank better in mobile search. Obviously, this will work only for signed-in users who have the app installed on their mobile devices.
What does this algorithm will actually do?
You must be knowing about GoogleBot. It will look at the UI of your website and not just see specific font sizes but see how a user would see the fonts on different mobile devices. This is not just about viewing website UI but about functioning too i.e. It also checks how a user will see page scrolling on a mobile interface. It checks buttons, labels are large enough for better UI and can click on.
GoogleBot renders the website page and finds out flaws like tiny fonts, big headers etc as a user would. To showcase an example, if HTML page has a 24px font size, then GoogleBot render it with JS and CSS, it might have new font size size to 10 px which leads to a bad user experience. Similar is the case when user tries to zoom and pan the website. GoogleBot will correlate it to a view port of the mobile device and would calculate the impact for the user.
To summarize, GoogleBot sees what a normal user see when browsing the website on mobile.
I have seen a lot of people talking about this change as harmful for business and search rankings. According to me, this change has a positive mindset towards the effectiveness of “Mobile Friendly” internet. This will make sure that companies provide a good UI support to its mobile users and help to grow mobile only users (who used to view websites as desktop view earlier.)