Q228- Bootstrap 4.5 vs Bootstrap 3 version difference

Bootstrap 4 is a major upgrade over Bootstrap 3, rebuilt with new technologies and better design systems.

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✅ 1. New Flexbox-Based Grid System (Major Change)

Bootstrap 4 uses Flexbox, while Bootstrap 3 uses float-based layout.

Bootstrap 3:

.col-md-4 { float: left; }

Bootstrap 4.5:

display: flex;

✔ Better alignment
✔ Easier vertical centering
✔ Equal height columns by default

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✅ 2. Rewritten in Sass Instead of Less

Bootstrap 3 → Less

Bootstrap 4 → Sass (.scss)

✔ Sass is more powerful
✔ Better mixins, variables, nesting
✔ Faster development

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✅ 3. Improved Grid Breakpoints

Bootstrap 4 added a new extra-large breakpoint and renamed sizes.

Bootstrap 3	Bootstrap 4.5
xs, sm, md, lg	xs, sm, md, lg, xl
No spacing utilities	Tons of spacing utilities

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✅ 4. Cards Replaced Panels, Wells, Thumbnails

Bootstrap 3 had:

• .panel
• .thumbnail
• .well

Bootstrap 4 replaced all of them with one unified component:

🎉 Cards

<div class="card">
  <div class="card-body">Content</div>
</div>

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✅ 5. Utility Classes Improved

Bootstrap 4 introduced hundreds of helper classes, like:

m-0, mt-3, p-4, text-center, d-flex, justify-content-between

Bootstrap 3 had very limited utilities.

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✅ 6. Buttons & Forms Redesigned

Bootstrap 4:

• Rounded buttons
• Better input groups
• Custom selects, checkboxes, radios
• Better spacing & alignment
• .form-group improved

Bootstrap 3 forms felt outdated.

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✅ 7. Typography Changes

Bootstrap 3:

• px-based fonts

Bootstrap 4:

• rem-based fonts
• Better responsive text
• New display headings: .display-1 to .display-4

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✅ 8. Improved JavaScript Components

Bootstrap 4 uses:

• ES6
• Tether/Popper.js for tooltips & popovers
• More stable modals

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✅ 9. New Reboot.css (Improved Normalize.css)

A modern CSS reset for consistent styling across browsers.

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🚫 10. Removed Features (Breaking Changes)

Bootstrap 4 removed:

• Glyphicons
• Panels, Wells, Thumbnails
• Affix plugin
• .input-group-addon
• Many old classes

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🎯 In Short:

Bootstrap 3

• Float-based grid
• Less
• Older UI components (panels, wells, thumbnails)
• Limited utilities
• Outdated forms and typography

Bootstrap 4.5

• Flexbox-based layout
• Sass
• Cards component
• More breakpoints
• Tons of utility classes
• Custom form controls
• Reboot.css reset
• Modern and responsive