document.getElementById("top").classList.add("fadeInAfterSecs"); Please follow this link. .fadeInAfterSecs { animation: fadeInAfter2Secs 1s; animation-delay: 2s; opacity: 0; animation-fill-mode: forwards; } @keyframes fadeInAfter2Secs { 0% { opacity: 0; } 100% { opacity: 1; } }