Bootstrap 5 (update 2021)
To right align elements in Bootstrap 5…
float-right is now float-end
text-right is now text-end
ml-auto is now ms-auto
Bootstrap 4 (original answer)
Use float-right for block elements, or text-right for inline elements:
<div class="row">
<div class="col">left</div>
<div class="col text-right">inline content needs to be right aligned</div>
</div>
<div class="row">
<div class="col">left</div>
<div class="col">
<div class="float-right">element needs to be right aligned</div>
</div>
</div>
http://codeply.com/go/oPTBdCw1JV
If float-right is not working, remember that Bootstrap 4 is now flexbox, and many elements are display:flex which can prevent float-right from working.
In some cases, the utility classes like align-self-end or ml-auto work to right align elements that are inside a flexbox container like the Bootstrap 4 .row, Card or Nav. The ml-auto (margin-left:auto) is used in a flexbox element to push elements to the right.
Bootstrap 4 align right examples