JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main">main</div>
<div class="footer">footer</div>

CSS

html, body {
    height: 100%;
}
body {
    display: table;
    width: 100%;
    margin: 0;
}
.main, .footer {
    display: table-row;
}
.main {
    height: 100%;
}
.footer {
    background: silver;
    /* height: 200px; */
}