CodePen Embed - scroll-behavior: smooth

<div id="box1" class="box1">
  <a href="#box2">
    <h2>test1</h2>
  </a>
</div>
<div id="box2" class="box2">
  <a href="#box1">
    <h2>test2</h2>
  </a>
</div>

html {
  scroll-behavior: smooth;
}

#box1 {
  height: 600px;
  background-color: red;
}

#box2 {
  height: 600px;
  background-color: yellow;
}

This Pen is owned by Sung Gyun Oh on CodePen.

See more by @salgum1114 on CodePen

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.