button {
  position: relative;
}

.copied::after {
  position: absolute;
  top: 12%;
  right: 110%;
  display: block;
  content: "Copiado";
  font-size: 0.75em;
  padding: 2px 3px;
  color: #fff;
  background-color: #5cb85c;
  border-radius: 3px;
  opacity: 0;
  will-change: opacity, transform;
  animation: showcopied 1.5s ease;
}

@keyframes showcopied {
  0% {
    opacity: 0;
    transform: translateX(100%);
  }
  70% {
    opacity: 1;
    transform: translateX(0);
  }
  100% {
    opacity: 0;
  }
}