Answers for "css add backdrop"

backdrop css

/* Backdrop is only displayed when dialog is opened with dialog.showModal() */
dialog::backdrop {
  background: rgba(255,0,0,.25);
}

how we use backdrop-filter css property

<div class="container">
  <div class="box">
    <p>backdrop-filter: blur(5px)</p>
  </div>
</div>