Add a red border to an element in Bootstrap to indicate danger

To add a red border to an element, you need to implement the border-danger class.

Red border implement danger and you can set danger messages inside it.

Implementing the border-danger is quite easy −

<div class="new border border-danger">
  Red Border
</div>

Let us see an example to work with the border-danger Bootstrap 4 class −

Example

Live Demo

<!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/4.1.0/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script>
    <style>
    .new {
      width: 120px;
      height: 120px;
      margin: 20px;
    }
    </style>
  </head>
<body>
  <div class="container">
    <p>Rectangle with red border:</p>
    <div class="new border border-danger">Red Border</div>
  </div>
</body>
</html>