Adds a fading gradient to an overflowing element to better indicate there is more content to be scrolled.

<div class="overflow-scroll-gradient">
  <div class="overflow-scroll-gradient__scroller">
    Lorem ipsum dolor sit amet consectetur adipisicing elit. <br />
    Iure id exercitationem nulla qui repellat laborum vitae, <br />
    molestias tempora velit natus. Quas, assumenda nisi. <br />
    Quisquam enim qui iure, consequatur velit sit? <br />
    Lorem ipsum dolor sit amet consectetur adipisicing elit.<br />
    Iure id exercitationem nulla qui repellat laborum vitae, <br />
    molestias tempora velit natus. Quas, assumenda nisi. <br />
    Quisquam enim qui iure, consequatur velit sit?
  </div>
</div>

.overflow-scroll-gradient {
  position: relative;
}
.overflow-scroll-gradient::after {
  content: '';
  position: absolute;
  bottom: 0;
  width: 250px;
  height: 25px;
  background: linear-gradient(
    rgba(255, 255, 255, 0.001),
    white
  ); /* transparent keyword is broken in Safari */
  pointer-events: none;
}
.overflow-scroll-gradient__scroller {
  overflow-y: scroll;
  background: white;
  width: 240px;
  height: 200px;
  padding: 15px;
  line-height: 1.2;
}

Explanation

1. position: relative on the parent establishes a Cartesian positioning context for pseudo-elements.
2. ::after defines a pseudo element.
3. background-image: linear-gradient(...) adds a linear gradient that fades from transparent to white (top to bottom).
4. position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
5. width: 240px matches the size of the scrolling element (which is a child of the parent that has the pseudo element).
6. height: 25px is the height of the fading gradient pseudo-element, which should be kept relatively small.
7. bottom: 0 positions the pseudo-element at the bottom of the parent.
8. pointer-events: none specifies that the pseudo-element cannot be a target of mouse events, allowing text behind it to still be selectable/interactive.

Browser support

• https://caniuse.com/#feat=css-gradients