Bootstrap columns stacking vertically on mobile device
Solution 1:
The columns are stacking vertically because you're using Bootstrap 4, and the -xs- infix is no longer used. Just use col-4..
<div class="container border-show center-div">
<div class="row">
<div class="col-4 border-show">1</div>
<div class="col-4 border-show">2</div>
<div class="col-4 border-show">3</div>
</div>
</div>
http://www.codeply.com/go/sCct2CzZte