blur shadow

HTML

<div>
  <h1>Hello world</h1>
</div>

CSS

body{
  background-image: url('https://dsc.cloud/78daed/h006_b_E01_k.jpg');
  background-size: cover;
  background-repeat: no-repeat;
  margin: 0; 
  padding-left: 50px;
  color: white;
  font-family: 'SF Pro Text', 'Arial', sans-serif;
  font-size: 50px;
}

h1{
  display: inline-block;
  position: relative;
  
}

h1::after{
  content: 'Hello world';
  color:rgba(255,255,255,0);
  backdrop-filter: blur(7px);
  filter: blur(25px);
  position: absolute;
  left:0;
  top:0;
  z-index:-2;
}