<button class="btn"> Button</button><br>
 <button class="btn btn-primary">Primary Button</button>
<button class="btn btn-secondary">Secondary Button</button>
<button class="btn btn-success">Success Button</button>
<button class="btn btn-warning">Warning Button</button>
<button class="btn btn-info btn-sm">Info Small Button</button>
<button class="btn btn-light">Light Button</button>
<button class="btn btn-dark">Dark Button</button>
<button class="btn btn-danger btn-lg">Danger Large Button</button> <br>

<button class="btn btn-danger btn-lg disabled"> Disabled</button>
<button class="btn btn-success btn-lg active">Active</button> <br> <br>

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.min.css

External JavaScript

This Pen doesn't use any external JavaScript resources.