JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div {
  height: 2px;
  width: 200px;
  margin: 30px auto;
  background: orange;
  animation-name: animationWidth;
  animation-duration: 1s;
  animation-fill-mode: forwards;
}

@keyframes animationWidth {
  0% {
    width: 0%;
  }
  100% {
    width: 200px;
  }
}