<div class="text-center">
  <h2>Resize this window to test the breakpoints</h2>
<a href="https://getbootstrap.com/docs/4.4/layout/overview/#responsive">Docs</a>
</div>


<div class="container-fluid">100% wide always</div>

<div class="container-sm">100% wide until small breakpoint</div>
<div class="container-md">100% wide until medium breakpoint</div>
<div class="container-lg">100% wide until large breakpoint</div>
<div class="container-xl">100% wide until extra large breakpoint</div>
div[class^="container"]  {
  border-bottom: 5px solid #ccc;
  padding:1rem;
  text-align:center;
}

External CSS

  1. https://jacoblett.github.io/bootstrap4-latest/bootstrap-4-latest.min.css

External JavaScript

  1. https://code.jquery.com/jquery-3.2.1.slim.min.js
  2. https://jacoblett.github.io/bootstrap4-latest/bootstrap-4-latest.min.js