JSFiddle - React, Tailwind, and code Playground

HTML

<!-- The background -->
<div class="bg-video">
  <video autoplay loop muted playsinline>
    <source src="https://www.w3schools.com/html/mov_bbb.mp4" type="video/mp4">
    <source src="https://www.w3schools.com/html/mov_bbb.ogg" type="video/ogg">
    Your browser does not support the video tag.
  </video>
</div>

<!-- The main container -->
<section class="main-container">
    <p>The content</p>
</section>

SCSS

.main-container {
   max-width: 500px;
   width: 100%;
   background: rgba(255,255,255,0.7);
   margin: auto;
   padding: 100px;
   position: relative;
   z-index: 1;
}
.bg-video {
   position: fixed;
   top: 0;
   left: 0;
   z-index: 0;
   width: 100vw;
   height: 100vh;
   video {
     width: auto;
     height: 100%;
   }
}