<div class="loader"></div>

.loader {
  width: 48px;
  height: 48px;
  border: 4px solid #e2e8f0;
  border-bottom-color: #3b82f6;
  border-radius: 50%;
  display: inline-block;
  box-sizing: border-box;
  animation: rotation 1s linear infinite;
}

@keyframes rotation {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}