center container in middle of page bootstrap code example
Example 1: bootstrap vertical align
<div class="d-flex align-items-start">...</div>
<div class="d-flex align-items-end">...</div>
<div class="d-flex align-items-center">...</div>
<div class="d-flex align-items-baseline">...</div>
<div class="d-flex align-items-stretch">...</div>
Example 2: 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>