<div class="fullscreen-video-container">

  <video autoplay loop muted>

    <source src="https://www.dropbox.com/scl/fi/eg0c3th4vyjnnz09cwxam/22512-328261507_tiny.mp4?rlkey=sk0uvs93a3uby17qbzdx1c3cx&raw=1" type="video/mp4">
>

  </video>
  
  <div class="fullscreen-video-content">

     <h1>Some Text</h1>

  </div>

</div>

* {
  margin: 0;
  padding: 0;
}

.fullscreen-video-container {
  position: relative;
  height: 100vh; 
  width: 100vw;
  overflow: hidden;
}

.fullscreen-video-container video {
  position: absolute;
  width: auto;
  height: auto;
  min-width: 100%;
  min-height: 100%;
  top: 50%;
  left: 50%;
  transform: translate(-50%,-50%);
  z-index : -1;
}