JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

html, body, div {
    /* Height and width fallback for older browsers. */
    height: 100%;
    width: 100%;
    
    /* Set the height to match that of the viewport. */
    height: 100vh;
    
    /* Set the width to match that of the viewport. */
    width: 100vw;
    
    /* Remove any browser-default margins. */
    margin: 0;
}

div {
    background: tomato;
}