Reply To: Bootstrap in Joomla template, reduce font size on small screen

[Atelierbram]

html {
 font-size: 16px;
}
.nav {
 font-size: 1em;
}
@media (max-width: 1024px) {
 .nav {
   font-size: 0.875rem;
 }
}

or mobile first approach:

.nav {
 font-size: 0.875em;
}
@media (min-width: 1024px) {
 .nav {
   font-size: 1rem;
 }
}