body::before {
    content: "";
    position: fixed;
    inset: 0;
    z-index: 1;
    pointer-events: none;

    background-image: url("https://static.tildacdn.com/tild3533-3461-4033-b136-363731633065/noise.gif");
    background-repeat: repeat;
    background-size: cover;

    opacity: 0.03; /* 3% */
}