how to blur background in firefox code example

Example: css backdrop filter

/* 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: unset;