timeline-scope

The timeline-scope CSS property modifies the scope of a named animation timeline.

By default, a named timeline (i.e. declared using scroll-timeline-name or view-timeline-name) can only be set as the controlling timeline of a direct descendant element (i.e. by setting animation-timeline on it with the timeline name as its value). This is the timeline's default "scope".

timeline-scope is given the name of a timeline defined on a descendant element; this causes the scope of the timeline to be increased to the element that timeline-scope is set on and any of its descendants. In other words, that element and any of its descendant elements can now be controlled using that timeline.

Note: If no timeline (or more than one timeline) exists with the name given for the timeline-scope value, an inactive timeline with the specified name is created.

Syntax

timeline-scope: none;
timeline-scope: custom_name_for_timeline;

Values

Allowed values for timeline-scope are:

none: There is no change in timeline scope.
<dashed-ident>: Specifies the name of an existing named timeline (i.e. declared using scroll-timeline-name or view-timeline-name) defined on a descendant element. This causes the timeline scope to be increased to the element that timeline-scope is set on and any of its descendants.

Note: <dashed-ident> values must start with --, which helps to avoid name clashes with standard CSS keywords.

Formal definition

Initial value	none
Applies to	all elements
Inherited	no
Computed value	the keyword none or a list of CSS identifiers
Animation type	not animatable

Formal syntax

none | <dashed-ident>#

Examples

In this example, a scroll timeline named --myScroller is defined using the scroll-timeline-name property on the element with the scroller class (the scrolling element). This is then applied to the animation on the element with the box and animation classes (the animated element) using animation-timeline: --myScroller. The key point to note here is that the animated element is not a descendant of the scrolling element — to make this work, we increase the scope of the --myScroller timeline by setting timeline-scope: --myScroller on the <body>.

HTML

The HTML for the example is shown below.

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

<div class="scroller">
  <div class="long-element"></div>
</div>

CSS

The CSS is as follows.

First of all, we set the <body>'s height to 100vh, and lay its two child elements out as two equal columns using flexbox. We also set timeline-scope: --myScroller on it so that the --myScroller timeline can be set as the controlling timeline for an animation set on the <body> and any element inside it.

body {
  margin: 0;
  height: 100vh;
  display: flex;

  /* increases the timeline scope from the .scroller <div> element
  to the whole <body> */
  timeline-scope: --myScroller;
}

.content,
.scroller {
  flex: 1;
}

Next, the scrolling element has the --myScroller timeline set on it, overflow so that it will scroll, and it is given a background color so that its boundary is clear to see. The scrolling element's child long element is given a large height so that the scrolling element will actually scroll.

.scroller {
  overflow: scroll;
  scroll-timeline-name: --myScroller;
  background: deeppink;
}

.long-element {
  height: 2000px;
}

Next, we give the animated element some rudimentary styling, and apply an animation to it. We also apply the --myScroller timeline to it using animation-timeline: --myScroller. To reiterate, this is only possible because earlier we set timeline-scope: --myScroller on the <body> element — the animated element is not a descendant of the scrolling element.

.box {
  width: 100px;
  height: 100px;
  border-radius: 10px;
  background-color: rebeccapurple;
  position: fixed;
  top: 20px;
  left: 0%;
}

.animation {
  animation: rotate-appear;
  animation-timeline: --myScroller;
}

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

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

Result

Scroll the vertical bar on the pink area to see the square animate.

css properties timeline-scope