<div class="panel">
  backdrop-filter
</div>
body{
  background: url("https://i.imgur.com/1XQmVnv.jpg") center center;
  background-size: cover;
}
.panel{
  margin: 10px;
  border-radius: 20px;
/*   background: #fff; */
  background-color: rgba(255, 255, 255, 0.3);
  padding: 20px;
/*   display: inline-block; */
  backdrop-filter: blur(10px);
  -moz-backdrop-filter: blur(10px);
  
}

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External JavaScript

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