Bootstrap - Mobile-first approach

The Mobile-first approach in Bootstrap means that web pages and applications are designed and built starting with mobile devices first, and then enhanced for larger screens (like tablets and desktops).

1. Concept

• The design starts with the smallest screen size (mobile).

• Then, you progressively add more styles and layout changes as the screen size increases.

• This ensures the site looks good and functions well on all devices.

2. How Bootstrap Implements It

• Bootstrap’s grid system and media queries are built around the mobile-first principle.

• By default, styles apply to mobile devices, and you use min-width media queries to apply styles for larger screens.

3. Example

<div class="col-12 col-md-6 col-lg-4">...</div>

Explanation:

• col-12: For extra small (mobile) screens, the element takes the full width (12 columns).

• col-md-6: For medium (tablet) screens and above, it takes half width (6 columns).

• col-lg-4: For large (desktop) screens and above, it takes one-third width (4 columns).

4. Why It’s Important

• Ensures better performance on mobile (less CSS, fewer resources).

• Provides progressive enhancement — builds up from a strong mobile base.

• Improves usability and accessibility for users on all devices.

5. In short:

Bootstrap’s mobile-first approach means you start with a layout that works on mobile screens by default, and then use responsive breakpoints to adapt it to larger devices.