Mobile-first indexing means Google primarily uses your website’s mobile version for ranking and indexing. Since a large majority of people browse on phones and tablets, Google looks at how your site performs on mobile devices before desktop computers. This makes it essential to ensure your website works well on small screens, loads quickly on mobile networks, and offers a smooth experience for mobile users.
See also: Responsive design, Performance testing
Further reading: What Are the Key Principles of Good Web Design?
