.urlbox-spinner {
  position: relative;
}

.urlbox-spinner::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 30px;
  height: 30px;
  margin: -15px 0 0 -15px;
  border: 5px solid #fff;
  border-top-color: #333;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}