carousel-fade

.carousel-fade .carousel-item {
  opacity: 0;
  transition-property: opacity;
  -webkit-transform: none;
  transform: none;
}

.carousel-fade .carousel-item.active,
.carousel-fade .carousel-item-next.carousel-item-left,
.carousel-fade .carousel-item-prev.carousel-item-right {
  z-index: 1;
  opacity: 1;
}

.carousel-fade .active.carousel-item-left,
.carousel-fade .active.carousel-item-right {
  z-index: 0;
  opacity: 0;
  transition: 0s 0.6s opacity;
}

@media (prefers-reduced-motion: reduce) {
  .carousel-fade .active.carousel-item-left,
  .carousel-fade .active.carousel-item-right {
    transition: none;
  }
}