Mobile-First: The Smartphone is the Planet's Main Screen

If you open the analytics of any modern website (except maybe B2B services for accountants), you'll see that 70-85% of traffic comes from mobile phones. Google realized this, and in 2019 made a fundamental shift by implementing Mobile-First Indexing.

What does this mean? Previously, the robot looked at your site through the eyes of a desktop user. Now, Googlebot pretends to be a mobile phone. Google evaluates your site EXCLUSIVELY based on its mobile version. The desktop version has become secondary.