JSFiddle - React, Tailwind, and code Playground

HTML

<html>
    <head></head>
    <body>
        <div class="full_size">Test</div>
    </body>
</html>

CSS

html, body, .full_size {
    height: 100%;
}

html {
    background-color: #99f;
}

body {
    padding: 20px;
}

.full_size {
    background-color: #9f9;
}