Mobile-first

The argument is simple. A phone screen cannot hold everything, so designing for it first forces the question of what matters most. Once that is settled, the desktop version is the mobile version with more room, rather than the desktop version being a full page that has to be squeezed. Squeezing is where mobile experiences go bad.

Mobile-first is also a technical convention. Styles are written for the narrow layout by default and then extended at wider breakpoints, which tends to produce smaller stylesheets and fewer overrides. Webflow works the other way round by default, cascading from desktop downward, which is worth knowing when a design was conceived mobile-first.

Whether to work this way depends on the audience. For most business sites the majority of visitors are on a phone and the buyers are often on a desktop, which means neither can be the afterthought. The useful discipline is deciding the priority order once and applying it at every width.