spinner.html

<div class="loader">
    <svg viewBox="0 0 32 32" width="32" height="32">
      <circle id="spinner" cx="16" cy="16" r="14" fill="none"></circle>
    </svg>
</div>

<style>
  .loader {
    left: 50%;
    top: 50%;
    position: fixed;
    -webkit-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
  }
  .loader #spinner {
    box-sizing: border-box;
    stroke: #673AB7;
    stroke-width: 3px;
    -webkit-transform-origin: 50%;
    transform-origin: 50%;
    -webkit-animation: line 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite, rotate 1.6s linear infinite;
    animation: line 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite, rotate 1.6s linear infinite;
  }
</style>