<div class="animate"></div>

body {
  display: grid;
  place-items: center;
  height: 100vh;
}

div {
  background: #ff7a18;
  height: 250px;
  width: 250px;
}

.animate {
  animation-duration: 0.5s;
  animation-name: animate-fade;
  animation-delay: 0.5s;
  animation-fill-mode: backwards;
}

@keyframes animate-fade {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}