scroll-timeline-axis

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The scroll-timeline-axis CSS property is used to specify the scrollbar direction that will be used to provide the timeline for a named scroll progress timeline animation, which is progressed through by scrolling a scrollable element (scroller) between top and bottom (or left and right). scroll-timeline is set on the scroller that will provide the timeline. See CSS scroll-driven animations for more details.

Note: If the scroller element does not overflow its container in the axis dimension or if the overflow is hidden or clipped, no scroll progress timeline will be created.

The scroll-timeline-axis and scroll-timeline-name properties can also be set using the scroll-timeline shorthand property.

Syntax

css

/* Logical property values */
scroll-timeline-axis: block;
scroll-timeline-axis: inline;
/* Non-logical property values */
scroll-timeline-axis: y;
scroll-timeline-axis: x;

Values

Allowed values for scroll-timeline-axis are:

block: The scrollbar on the block axis of the scroller element, which is the axis in the direction perpendicular to the flow of text within a line. For horizontal writing modes, such as standard English, this is the same as y, while for vertical writing modes, it is the same as x. This is the default value.
inline: The scrollbar on the inline axis of the scroller element, which is the axis in the direction parallel to the flow of text in a line. For horizontal writing modes, this is the same as x, while for vertical writing modes, this is the same as y.
y: The scrollbar on the vertical axis of the scroller element.
x: The scrollbar on the horizontal axis of the scroller element.

Formal definition

Initial value	`block`
Applies to	scroll containers
Inherited	no
Computed value	as specified
Animation type	Not animatable

Formal syntax

scroll-timeline-axis = 
  [ block | inline | x | y ]#

Examples

Defining the axis of the scroll progress timeline

In this example, a scroll progress timeline named --myScroller is defined using the scroll-timeline-name property on the :root element (<html>). This timeline is then applied to the animation on the element with the animation class using animation-timeline: --myScroller.

To demonstrate the effect of scroll-timeline-axis, a horizontal (non-default) scrollbar is used in this example to drive the animation.

HTML

The HTML for the example is shown below.

html

<body>
  <div class="content"></div>
  <div class="box animation"></div>
</body>

CSS

The CSS for the container sets the :root as the source of a scroll progress timeline named --myScroller using the scroll-timeline-name property. The scroll axis is set using scroll-timeline-axis: x; (Chromium) and scroll-timeline-axis: horizontal; (Firefox) — this causes the horizontal scrollbar position to determine the animation timeline.

The width of the .content element is set to a large value to make it overflow the :root element.

Also worth noting is that the .animation element has the timeline applied to it using animation-timeline: --myScroller;, and it also has an animation-duration applied to it so that the example will work in Firefox.

css

:root {
  scroll-timeline-name: --myScroller;

  /* Chromium supports the new x/y syntax */
  scroll-timeline-axis: x;
  /* Firefox still supports the old horizontal/vertical syntax */
  scroll-timeline-axis: horizontal;
}

body {
  margin: 0;
  overflow-y: hidden;
}

.content {
  height: 100vh;
  width: 2000px;
}

.box {
  width: 100px;
  height: 100px;
  border-radius: 10px;
  background-color: rebeccapurple;
  position: fixed;
  top: 25px;
  left: 25px;
}

.animation {
  animation: rotate-appear;
  animation-timeline: --myScroller;
  animation-duration: 1ms; /* Firefox requires this to apply the animation */
}

@keyframes rotate-appear {
  from {
    rotate: 0deg;
    top: 0%;
  }

  to {
    rotate: 720deg;
    top: 100%;
  }
}

Result

Scroll the horizontal bar at the bottom to see the square animate as you scroll.

Specifications

Specification
Scroll-driven Animations # propdef-scroll-timeline-axis