Run Example

Edit This Code:
<!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/3.4.0/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/js/bootstrap.min.js"></script>
</head>
<body>

 <h1> This is Heading 1 in Bootstrap. </h1>
 <h2> This is Heading 2 in Bootstrap. </h2>
 <h3> This is Heading 3 in Bootstrap. </h3>
 <h4> This is Heading 4 in Bootstrap. </h4>
 <h5> This is Heading 5 in Bootstrap. </h5>
 <h6> This is Heading 6 in Bootstrap. </h6>

</body>
</html>
Result: