<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!------ Include the above in your HEAD tag ---------->
<body>
<div class="container">
<div class="row ">
<h1 class="text-center col-12">
How to Vertical Align Center in Bootstrap 4
<small class="by">by Shurvir Mori</small>
</h1>
</div>
</div>
</body>
body {
display:flex;
align-items:center;
min-height:100vh;
}