Bootstrap 4 Vertical Align not working - css

Question

I'm making a very simple form for an Electron app I am making to experiment with the software, however, I am stuck on the most basic of things... the interface design.
I'm using Bootstrap 4 for my interface and am trying to centre the form vertically, however, I am getting mix results using various suggestions made on other's questions on the same topic. They either do not work or squeeze all my content onto a single line and generally mess the current layout up.
Any suggestions on how I can vertically align the items in the container below?
<!-- Search Field -->
<div class="container">
<div class="row justify-content-center">
<div class="col-sm-auto">
<h1 class="text-white">Shorten M' URL!</h1>
</div>
</div>
<div class="row justify-content-center">
<div class="col-sm-6">
<div class="input-group">
<input type="text" class="form-control" placeholder="Enter URL...">
<span class="input-group-btn">
<button class="btn btn-primary" type="button">Shorten!</button>
</span>
</div>
</div>
</div>
</div>

Answer 1

Are you looking for this?:
.vh-100 {
height: 100vh;
}
<div class="container vh-100 bg-dark">
<div class="row vh-100 justify-content-center align-items-center">
<div class="col-6 text-center">
<h1 class="text-white">Shorten M' URL!</h1>
<br>
<div class="input-group">
<input type="text" class="form-control" placeholder="Enter URL...">
<span class="input-group-btn">
<button class="btn btn-primary" type="button">Shorten!</button>
</span>
</div>
</div>
</div>
</div>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css" rel="stylesheet"/>
Basically you have to have the container to fit the screen height. Once there, you can align it's items vertically.