How do you decrease navbar height in Bootstrap 4?

Decreasing the Navbar height is easier in Bootstrap 4 using the spacing utils. The height of the navbar comes from padding in the Navbar contents.

Just use py-0 in the nav-link and navbar-text..

<nav class="navbar navbar-collapse navbar-toggleable-md navbar-light bg-faded ">
    <div class="collapse navbar-collapse" id="navbarText">
        <ul class="navbar-nav mr-auto">
            <li class="nav-item">
                <a class="nav-link py-0">
                    <span class="icon icon18 icon-upload"></span> Input Data From Prior Month
                </a>
            </li>
            <li class="nav-item">
                <a class="nav-link py-0">
                    <span class="icon icon18 icon-excel-file"></span> Export to Excel
                </a>
            </li>
        </ul>
        <span class="navbar-text py-0 color-blue">
        *Data Automatically pulled from sources
      </span>
    </div>
</nav>

The py-0 class sets padding-top:0;padding-bottom:0 on the items.

Bootstrap 4 Navbar Shrink Height

If anyone like changing CSS to get the same result, try this method. In my case I have just changed the .navbar min-height and the links font-size and it decreased the navbar.

For example:

.navbar{
    min-height:12px;
}
.navbar  a {
    font-size: 11.2px;
}

And this also worked for increasing the navbar height.

This also helps to change the navbar size when scrolling down the browser.