Responsive Web Design: Building Sites That Work Everywhere

Responsive web design (RWD) ensures your website looks great and functions well on any device — from large desktop monitors to small smartphone screens. In this guide, we'll cover the essential techniques for building responsive websites.

The Foundation: Viewport Meta Tag

Always include this meta tag in your HTML:

This tells browsers to:

• Set the viewport width to the device width
• Set the initial zoom level to 100%

Without this, mobile browsers will render the page as if it were a desktop site and scale it down.

Mobile-First Design

Mobile-first means designing for small screens first, then adding styles for larger screens:

/ Base styles (mobile) /
.container {
    padding: 15px;
}
.card {
    width: 100%;
    margin-bottom: 15px;
}
/ Tablet and up /
@media (min-width: 768px) {
    .container {
        padding: 30px;
    }
    .card {
        width: 48%;
    }
}
/ Desktop and up /
@media (min-width: 1024px) {
    .container {
        padding: 50px;
        max-width: 1200px;
        margin: 0 auto;
    }
    .card {
        width: 32%;
    }
}

Why Mobile-First?

• Performance — Mobile devices receive only the CSS they need
• Progressive enhancement — Core functionality works everywhere
• Cleaner code — Start simple, add complexity as needed

Media Queries

Media queries apply styles based on device characteristics:

/ Width-based (most common) /
@media (min-width: 768px) { }
@media (max-width: 767px) { }
/ Range /
@media (min-width: 768px) and (max-width: 1023px) { }
/ Orientation /
@media (orientation: portrait) { }
@media (orientation: landscape) { }
/ Prefer reduced motion (accessibility) /
@media (prefers-reduced-motion: reduce) {
    * {
        animation: none !important;
        transition: none !important;
    }
}
/ Dark mode preference /
@media (prefers-color-scheme: dark) {
    body {
        background: #1a1a1a;
        color: #f0f0f0;
    }
}

Common Breakpoints

/ Mobile: 0 - 767px (default styles) /
/ Tablet: 768px - 1023px /
@media (min-width: 768px) { }
/ Desktop: 1024px - 1279px /
@media (min-width: 1024px) { }
/ Large Desktop: 1280px+ /
@media (min-width: 1280px) { }

Flexible Units

Relative Units

/ rem - relative to root font size (usually 16px) /
.heading {
    font-size: 2rem;    / 32px /
    margin-bottom: 1rem; / 16px /
}
/ em - relative to parent font size /
.card-title {
    font-size: 1.5em;
}
/ Viewport units /
.hero {
    height: 100vh;      / Full viewport height /
    width: 100vw;       / Full viewport width /
}
/ Percentages /
.sidebar {
    width: 30%;
}

The clamp() Function

Create fluid typography without media queries:

.heading {
    / Minimum, preferred, maximum /
    font-size: clamp(1.5rem, 4vw, 3rem);
}
.container {
    width: clamp(300px, 90%, 1200px);
}

Flexible Images

Make images responsive:

img {
    max-width: 100%;
    height: auto;
}

For background images:

.hero {
    background-image: url('hero.jpg');
    background-size: cover;
    background-position: center;
}

Responsive Images in HTML

    srcset="small.jpg 480w,
            medium.jpg 768w,
            large.jpg 1200w"
    sizes="(max-width: 480px) 480px,
           (max-width: 768px) 768px,
           1200px"
    src="large.jpg"
    alt="Responsive image"
>


    
    
    

Responsive Patterns

Responsive Navigation

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px;
}
.nav-links {
    display: none;
    flex-direction: column;
    position: absolute;
    top: 60px;
    left: 0;
    right: 0;
    background: white;
}
.nav-links.active {
    display: flex;
}
.menu-toggle {
    display: block;
}
@media (min-width: 768px) {
    .nav-links {
        display: flex;
        flex-direction: row;
        position: static;
        background: none;
    }
    .menu-toggle {
        display: none;
    }
}

Responsive Grid

.grid {
    display: grid;
    gap: 20px;
    grid-template-columns: 1fr; / Mobile: 1 column /
}
@media (min-width: 768px) {
    .grid {
        grid-template-columns: repeat(2, 1fr); / Tablet: 2 columns /
    }
}
@media (min-width: 1024px) {
    .grid {
        grid-template-columns: repeat(3, 1fr); / Desktop: 3 columns /
    }
}

Or use auto-fit for automatic responsiveness:

.grid {
    display: grid;
    gap: 20px;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

Testing Responsive Design

In ProLiveEditor

Use the Desktop/Mobile toggle to test your responsive designs:

• Write your CSS with mobile-first styles
• Add media queries for larger screens
• Toggle between views to see the results

Browser DevTools

• Open DevTools (F12)
• Click the device toolbar icon
• Select different device presets or set custom dimensions

Complete Responsive Page Example

Try this in ProLiveEditor:

    

        
My Responsive Site

    
    

        
Card 1

        
Card 2

        
Card 3

    
    

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
.page {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}
.header {
    padding: 20px;
    background: #3498db;
    color: white;
    text-align: center;
}
.main {
    flex: 1;
    padding: 20px;
    display: grid;
    gap: 20px;
    grid-template-columns: 1fr;
}
.card {
    background: #f9f9f9;
    padding: 30px;
    border-radius: 8px;
    text-align: center;
}
.footer {
    padding: 20px;
    background: #34495e;
    color: white;
    text-align: center;
}
@media (min-width: 768px) {
    .main {
        grid-template-columns: repeat(2, 1fr);
    }
}
@media (min-width: 1024px) {
    .main {
        grid-template-columns: repeat(3, 1fr);
        max-width: 1200px;
        margin: 0 auto;
    }
}

Practice building responsive layouts in ProLiveEditor — toggle between Desktop and Mobile views to test your designs!