Mobile-first design means building apps and websites starting with phones in...

https://fair-wiki.win/index.php/Why_Do_Big_Hero_Images_Make_My_Site_Feel_Slow_on_Phones%3F

Mobile-first design means building apps and websites starting with phones in mind. It focuses on making it fast to load, easy to tap buttons with your fingers, and simple to find what you need without extra clutter