Bootstrap 4 Grid Inspector
<!-- DEBUG -->
<div style="position: fixed; z-index:999; bottom:0;">
<span class="label label-default visible-xl-up hidden-lg-down">XL</span>
<span class="label label-success visible-lg-up hidden-xl-up hidden-md-down">LG</span>
<span class="label label-info visible-md-up hidden-lg-up hidden-sm-down">MD</span>
<span class="label label-primary visible-sm-up hidden-md-up hidden-xs-down">SM</span>
<span class="label label-warning visible-xs-up hidden-sm-up">XS</span>
</div>
<!-- /DEBUG -->