backdrop-filter CSS property applies effects to the area behind an element. That's nice to make a semi-transparent layer and blur anything behind. All CSS properties /* Keyword value */ backdrop-filter: none; /* URL to SVG filter */ backdrop-filter: url(commonfilters.svg#filter); /* <filter-function> values */ backdrop-filter: blur(2px); backdrop-filter: brightness(60%); backdrop-filter: contrast(40%); backdrop-filter: drop-shadow(4px 4px 10px blue); backdrop-filter: grayscale(30%); backdrop-filter: hue-rotate(120deg); backdrop-filter: invert(70%); backdrop-filter: opacity(20%); backdrop-filter: sepia(90%); backdrop-filter: saturate(80%); /* Multiple filters */ backdrop-filter: url(filters.svg#filter) blur(4px) saturate(150%); /* Global values */ backdrop-filter: inherit; backdrop-filter: initial; backdrop-filter: revert; backdrop-filter: unset;