scroll-marker-group

after

A ::scroll-marker-group pseudo-element is generated as a sibling of the scroll container's child DOM elements, immediately preceding them, and any generated ::scroll-button() pseudo-elements. It appears at the end of the container's tab order and layout box order (but not DOM structure).

before

A ::scroll-marker-group pseudo-element is generated as a sibling of the scroll container's child DOM elements, immediately preceding them, and any generated ::scroll-button() pseudo-elements. The scroll marker group appears at the start of the container's tab order and layout box order.

none

No ::scroll-marker-group pseudo-element will be generated on the element. This is the default value.

scroll-marker-group = 
  none    |
  before  |
  after   

See Creating CSS carousels for full examples that use the scroll-marker-group property.

In this example, we demonstrate the three values of the scroll-marker-group property.

HTML

We have a basic HTML <ul> list with several <li> list items.

<fieldset>
  <legend>Select <code>scroll-marker-group</code> value:</legend>
  <label><input type="radio" name="p" value="before" />before</label>
  <label><input type="radio" name="p" value="after" checked />after</label>
  <label><input type="radio" name="p" value="none" />none</label>
</fieldset>

<ul>
  <li>Item 1</li>
  <li>Item 2</li>
  <li>Item 3</li>
  <li>Item 4</li>
  <li>Item 5</li>
  <li>Item 6</li>
  <li>Item 7</li>
  <li>Item 8</li>
</ul>

CSS

We convert our <ul> into a carousel by setting the display to flex, creating a single, non-wrapping row of <li> elements. The overflow-x property is set to auto, meaning if the items overflow their container on the x-axis, the content will scroll horizontally. We then convert the <ul> into a scroll-snap container, ensuring that items always snap into place when the container is scrolled with a scroll-snap-type value of mandatory.

We create a scroll marker group with the scroll-marker-group property, placing the group after all the content.

ul {
  display: flex;
  gap: 4vw;
  padding-left: 0;
  margin: 32px 0;
  overflow-x: auto;
  overscroll-behavior-x: contain;
  scroll-snap-type: x mandatory;

  scroll-marker-group: after;
}

Next, we style the <li> elements, using the flex property to make them 33% of the width of the container. The scroll-snap-align value of start makes the left-hand side of the left-most visible item snap to the left edge of the container when the content is scrolled.

li {
  list-style-type: none;
  background-color: #eee;
  flex: 0 0 33%;
  scroll-snap-align: start;
  text-align: center;
  line-height: 5;
}

We then use the ::scroll-marker pseudo-element to create a square marker for each list item with a red border, and apply styles to the ::scroll-marker-group pseudo-element to lay out the scroll markers in a row with a 0.2em gap between each one.

li::scroll-marker {
  content: " ";
  border: 1px solid red;
  height: 1em;
  width: 1em;
}

::scroll-marker-group {
  display: flex;
  gap: 0.2em;
}

Finally, to ensure good user experience, we style the marker of the currently-scrolled element differently from the others, targeting the marker with the :target-current pseudoclass.

::scroll-marker:target-current {
  background: red;
}

fieldset {
  width: 20em;
}

label {
  font-family: monospace;
  display: block;
}

:has([value="before"]:checked) ul {
  scroll-marker-group: before;
}
:has([value="after"]:checked) ul {
  scroll-marker-group: after;
}

:has([value="none"]:checked) ul {
  scroll-marker-group: none;
}

Result

Note the placement of the scroll marker group. Check out how the keyboard tabbing order is different for before versus after, and note how the group disappears when the value is set to none.

• ::scroll-button()
• ::scroll-marker-group
• ::scroll-marker
• :target-current
• Creating CSS carousels
• CSS overflow module
• CSS Carousel Gallery via chrome.dev (2025)