bootstrap 4 div centro
<div class="d-flex justify-content-start">...</div>
<div class="d-flex justify-content-end">...</div>
<div class="d-flex justify-content-center">...</div>
<div class="d-flex justify-content-between">...</div>
<div class="d-flex justify-content-around">...</div>
alineación vertical de bootstrap
<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>
contenido de bootstrap col center
<div class="row">
<div class="col-4 d-flex justify-content-center text-center">
// for image and text
</div>
</div>
alinear columnas en el centro de bootstrap
<!-- Center columns in a Row -->
<div class="row d-flex justify-content-center text-center">
<div class="col-4">
// Add Content
</div>
<div class="col-4">
// Add Content
</div>
<div class="col-4">
// Add Content
</div>
</div>
centralizar div bootstrap
<div class="row align-items-center justify-content-center">
<div class="col">This will be centered vertically and horizontally</div>
</div>
bootstrap fila no-wrap
<div class="row flex-nowrap">
<div class="col"></div>
<div class="col"></div>
</div>