Mobile-first design means creating apps or websites with phones in mind first....

https://ricardosinterestingwords.swiftnestly.com/posts/how-to-reduce-friction-for-mobile-users-who-are-commuting

Mobile-first design means creating apps or websites with phones in mind first. It’s all about fast loading, easy-to-tap buttons, and simple menus that make finding what you need quick and hassle-free