background opacity css. code example
Example 1: css opacity background color
background: rgba(255, 255, 255, 0.25);
Example 2: transparent background css
div {
width: 200px;
height: 200px;
display: block;
position: relative;
}
div::after {
content: "";
background: url(image.jpg);
opacity: 0.5;
top: 0;
left: 0;
bottom: 0;
right: 0;
position: absolute;
z-index: -1;
}