filter vs backdrop-filter

.backdrop {
  position: fixed;
  top: 0;
  left: 0;
  height: 100vh;
  width: 100%;
  z-index: 20;
  filter: blur(4px);
  background-color: rgba(0, 0, 0, 0.5);
}

.backdrop {
  position: fixed;
  top: 0;
  left: 0;
  height: 100vh;
  width: 100%;
  z-index: 20;
  filter: blur(4px);
  background-color: rgba(0, 0, 0, 0.5);
}