Run Example

Edit This Code:
<!DOCTYPE html>
<html>
<head>
  <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>

<div class="container">
  <h2>Collapsible Panel</h2>
  <div class="panel-group">
    <div class="panel panel-default">
      <div class="panel-heading">
        <h4 class="panel-title">
          <a href="#text1" data-toggle="collapse"> Collapsible panel </a>
        </h4>
      </div>
      <div id="text1" class="panel-collapse collapse">
        <div class="panel-body">Panel body</div>
        <div class="panel-footer">Panel footer</div>
      </div>
    </div>
  </div>
</div>
    
</body>
</html>
Result: