<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h1>Responsive Containers</h1>
<p>Resize the browser window to see the effect.</p>
</div>
<div class="container-sm border">.container-sm</div>
<div class="container-md mt-3 border">.container-md</div>
<div class="container-lg mt-3 border">.container-lg</div>
<div class="container-xl mt-3 border">.container-xl</div>
</body>
</html>