Answers for "opacity of the background image css"

background-image: url opacity

background-image: url(IMAGE_URL); /* fallback for older browsers */

background-image: linear-gradient(to bottom, rgba(0,0,0,0.6) 0%,rgba(0,0,0,0.6) 100%), url(IMAGE_URL);

background image opacity css

body::before{
    content: "";
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    z-index: -1;
    background-image: url(image.jpg); /*Put your image url*/
    background-size: cover;
    background-position: center;
    opacity: 0.25; /*Value from 0.0 to 1.0*/
}

image opacity in html

img {
  opacity: 0.5;
}