Elizabeth Mosley

The approach you choose for responsive design affects everything from CSS organization to performance. Neither is universally "correct," but mobile-first has become the industry standard for good reason.

Mobile-First Philosophy

Start with mobile styles as your base, then add complexity for larger screens:

/* Base mobile styles */
.container {
  padding: 15px;
  font-size: 16px;
}

/* Tablet and up */
@media (min-width: 768px) {
  .container {
    padding: 30px;
    font-size: 18px;
  }
}

/* Desktop */
@media (min-width: 1024px) {
  .container {
    max-width: 1200px;
    margin: 0 auto;
  }
}

Why Mobile-First Wins

1. Performance: Mobile users download only mobile CSS, not unused desktop styles
2. Progressive Enhancement: Adding features is easier than removing them
3. Focus: Forces prioritization of essential content
4. Reality: Mobile traffic often exceeds desktop

Desktop-First Use Cases

Desktop-first still makes sense for:

• Internal business applications used primarily on workstations
• Data-heavy dashboards
• Complex design tools
• Legacy projects with established desktop designs

/* Desktop base */
.sidebar {
  width: 300px;
  float: left;
}

/* Mobile adjustments */
@media (max-width: 768px) {
  .sidebar {
    width: 100%;
    float: none;
  }
}

Breakpoint Strategy

Avoid device-specific breakpoints. Instead, let your content determine breaks:

• Don't: 320px (iPhone), 768px (iPad), 1024px (Desktop)
• Do: Where your design naturally needs adjustment

Common breakpoint ranges:

• Small: 0-640px
• Medium: 641-1024px
• Large: 1025px+

Testing Approach

Test at multiple sizes, not just breakpoints:

• Use browser dev tools
• Test on real devices
• Check between breakpoints (900px, 1100px)
• Verify touch targets are adequate (44x44px minimum)

Mobile-first development aligns with modern web usage patterns and creates faster, more focused experiences.

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