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 across my portfolio and client projects.