Definition :
The active selector is used to select and style the active link, a link becomes active when you click on it.
Program :
<html>
<head>
<meta name=”viewport” content=”width=device-width” initial scale=”1″>
<link rel=”stylesheet” href=”https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css”>
<script src=”https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js”> </script>
<script src=”https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.bundle.min.js”> </script>
</head>
<body>
<div class=”container” style=”border: 1px solid red;”>
<button class=”btn btn-primary active”> HELLO </button> </br>
<button class=”btn btn-primary disabled”> HELLO </button> </br>
</div>
</body>
</html>