JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container-fluid">
    <div class="navbar"></div>
    <div class="body">
        <p>content</p>
    </div>
</div>

CSS

body, html, .container-fluid, .sidebar, .body {
    height: 100%;
    min-height: 100%;
    margin:0;
}
.body {
    box-sizing: border-box;
    padding-top:40px;
    background:red;
    z-index:1;
}
.navbar {
    height: 40px;
    position: absolute;
    top: 0;
    left:0;
    width:100%;
    background:green;
    z-index:2;
}