Responsive design: complete guide
Principles and best practices for building sites that work on all devices.
Responsive design is the practice of creating websites that adapt gracefully to all devices: mobiles, tablets, laptops and large screens.
Today, it is no longer optional – most web traffic comes from smartphones, and search engines penalise sites that are not mobile‑friendly.
The principles of responsive design
Flexible layouts
Instead of fixed pixel widths, responsive sites use:
- Percentages and relative units
- Flexbox and CSS Grid
- Breakpoints to change layout at certain screen sizes
Adapted typography
On small screens:
- Font sizes must remain readable
- Line length should not be too long
- Spacing must be generous enough to avoid clutter
Touch‑friendly interactions
Buttons and links need:
- Enough size and spacing for fingers
- Clear visual feedback on tap
- Avoidance of tiny “tap targets” next to each other
Responsive design, performance and accessibility
A good responsive design also:
- Avoids loading massive images on mobile
- Maintains sufficient colour contrast in all versions
- Keeps navigation simple and consistent
These aspects are crucial for both accessibility and SEO.
I explore this further in my articles on web accessibility and UX/UI and conversion.
How I approach responsive design in my projects
When I build a custom site, I design for mobile and desktop from the beginning:
- Wireframes include both mobile and desktop layouts
- Component systems are designed to be reusable at different breakpoints
- I test on real devices, not just in the browser’s responsive mode
You can see the result on my own portfolio and other client projects.