How do you decrease navbar height in Bootstrap 3?

bootstrap had 15px top padding and 15px bottom padding on .navbar-nav > li > a so you need to decrease it by overriding it in your css file and .navbar has min-height:50px; decrease it as much you want.

for example

.navbar-nav > li > a {padding-top:5px !important; padding-bottom:5px !important;}
.navbar {min-height:32px !important}

add these classes to your css and then check.

Minder Saini's example above almost works, but the .navbar-brand needs to be reduced as well.

A working example (using it on my own site) with Bootstrap 3.3.4:

.navbar-nav > li > a, .navbar-brand {
    padding-top:5px !important; padding-bottom:0 !important;
    height: 30px;
}
.navbar {min-height:30px !important;}

Edit for Mobile... To make this example work on mobile as well, you have to change the styling of the navbar toggle like so

.navbar-toggle {
     padding: 0 0;
     margin-top: 7px;
     margin-bottom: 0;
}