bootstrap center item on entire page 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: centralize div bootstrap
<div class="row align-items-center justify-content-center">
<div class="col">This will be centered vertically and horizontally</div>
</div>