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 animation-range-start CSS property is used to set the start of an animation's attachment range along its timeline, i.e. where along the timeline an animation will start.

The animation-range-start and animation-range-end properties can also be set using the animation-range shorthand property.

Note: animation-range-start is included in the animation shorthand as a reset-only value. This means that including animation resets a previously-declared animation-range-start value to normal, but a specific value cannot be set via animation. When creating CSS scroll-driven animations, you need to declare animation-range-start after declaring any animation shorthand for it to take effect.


/* Keyword or length percentage value */
animation-range-start: normal;
animation-range-start: 20%;
animation-range-start: 100px;

/* Named timeline range value */
animation-range-start: cover;
animation-range-start: contain;
animation-range-start: cover 20%;
animation-range-start: contain 100px;


Allowed values for animation-range-start are normal, a <length-percentage>, a <timeline-range-name>, or a <timeline-range-name> with a <length-percentage> following it. See animation-range for a detailed description of the available values.

Also check out the View Timeline Ranges Visualizer, which shows exactly what the different values mean in an easy visual format.

Formal definition

Initial valuenormal
Applies toall elements
PercentagesRelative to the specified named timeline range if specified, otherwise relative to the entire timeline
Computed valueA list where each item may be 'normal', a length percentage, or a timeline range name and a length percentage
Animation typeNot animatable

Formal syntax

animation-range-start = 
[ normal | <length-percentage> | <timeline-range-name> <length-percentage>? ]#

<length-percentage> =
<length> |


Creating a named view progress timeline with range start

A view progress timeline named --subjectReveal is defined using the view-timeline property on a subject element with a class of animation. This is then set as the timeline for the same element using animation-timeline: --subjectReveal;. The result is that the subject element animates as it moves upwards through the document as it is scrolled.

An animation-range-start declaration is also set to make the animation begin later than expected.


The HTML for the example is shown below.

<div class="content">

    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
    tempor incididunt ut labore et dolore magna aliqua. Risus quis varius quam
    quisque id. Et ligula ullamcorper malesuada proin libero nunc consequat
    interdum varius. Elit ullamcorper dignissim cras tincidunt lobortis feugiat
    vivamus at augue.

    Dolor sed viverra ipsum nunc aliquet. Sed sed risus pretium quam vulputate
    dignissim. Tortor aliquam nulla facilisi cras. A erat nam at lectus urna
    duis convallis convallis. Nibh ipsum consequat nisl vel pretium lectus.
    Sagittis aliquam malesuada bibendum arcu vitae elementum. Malesuada bibendum
    arcu vitae elementum curabitur vitae nunc sed velit.

  <div class="subject animation"></div>

    Adipiscing enim eu turpis egestas pretium aenean pharetra magna ac. Arcu
    cursus vitae congue mauris rhoncus aenean vel. Sit amet cursus sit amet
    dictum. Augue neque gravida in fermentum et. Gravida rutrum quisque non
    tellus orci ac auctor augue mauris. Risus quis varius quam quisque id diam
    vel quam elementum. Nibh praesent tristique magna sit amet purus gravida
    quis. Duis ultricies lacus sed turpis tincidunt id aliquet. In egestas erat
    imperdiet sed euismod nisi. Eget egestas purus viverra accumsan in nisl nisi
    scelerisque. Netus et malesuada fames ac.


The subject element and its containing content element are styled minimally, and the text content is given some basic font settings:

.subject {
  width: 300px;
  height: 200px;
  margin: 0 auto;
  background-color: deeppink;

.content {
  width: 75%;
  max-width: 800px;
  margin: 0 auto;

h1 {
  font-family: Arial, Helvetica, sans-serif;

h1 {
  font-size: 3rem;

p {
  font-size: 1.5rem;
  line-height: 1.5;

The <div> with the class of subject is also given a class of animation — this is where view-timeline is set to define a named view progress timeline. It is also given an animation-timeline name with the same value to declare that this will be the element animated as the view progress timeline is progressed. We also give it an animation-range-start declaration to make the animation begin later than expected.

Last, an animation is specified on the element that animates its opacity and scale, causing it to fade in and size up as it moves up the scroller.

.animation {
  view-timeline: --subjectReveal block;
  animation-timeline: --subjectReveal;

  animation-name: appear;
  animation-range-start: entry 25%;
  animation-fill-mode: both;
  animation-duration: 1ms; /* Firefox requires this to apply the animation */

@keyframes appear {
  from {
    opacity: 0;
    transform: scaleX(0);

  to {
    opacity: 1,
    transform: scaleX(1);


Scroll to see the subject element being animated.


Scroll-driven Animations
# animation-range-start

Browser compatibility

BCD tables only load in the browser

See also