JSFiddle - React, Tailwind, and code Playground

HTML

<div class="simple_animation"></div>

CSS

html, body { margin: 0; } /* Prevent scrollbar */

div.simple_animation{
  width: 100px;
  height: 100px;
  background: red;
  animation: 5s loading forwards;
}

@keyframes loading {
  to {
    width: 100vw;
  }
}