For most sites, more than half of visitors arrive on a phone. Designing for desktop first and “shrinking it down” later almost always produces a worse mobile experience than designing mobile-first from the start.
What mobile-first actually means
It’s not just a smaller layout — it’s designing the core experience for the most constrained context first, then progressively enhancing for larger screens. Constraints force you to prioritize what actually matters.
Practical habits
- Design the smallest breakpoint first, then expand
- Keep tap targets at least 44x44px
- Trim navigation to essentials on small screens
- Test on an actual device, not just a resized browser window
If a design works well on a phone, it’s usually easy to expand for desktop. The reverse is rarely true.