You must have 2 classes, the fa
class and the class that identifies the desired icon fa-twitter
, fa-search
, etc …
<!-- Wrong -->
<i class="fa-search"></i>
<!-- Correct -->
<i class="fa fa-search"></i>
Bootstrap 5 update
Note: “The fa prefix has been deprecated in version 5. The new default is the fas solid style and the fab style for brands.” – Terje Solem