class for vertical center in bootstrap w3 school code example
Example: bootstrap div vertical center
<div class="jumbotron d-flex align-items-center min-vh-100">
<div class="container text-center">
I am centered vertically
</div>
</div>
<div class="jumbotron d-flex align-items-center min-vh-100">
<div class="container text-center">
I am centered vertically
</div>
</div>