animation-range

This property is a shorthand for the following CSS properties:

• animation-range-start
• animation-range-end

/* single keyword or length percentage value */
animation-range: normal; /* Equivalent to normal normal */
animation-range: 20%; /* Equivalent to 20% normal */
animation-range: 100px; /* Equivalent to 100px normal */

/* single named timeline range value */
animation-range: cover; /* Equivalent to cover 0% cover 100% */
animation-range: contain; /* Equivalent to contain 0% contain 100% */
animation-range: cover 20%; /* Equivalent to cover 20% cover 100% */
animation-range: contain 100px; /* Equivalent to contain 100px cover 100% */

/* two values for range start and end */
animation-range: normal 25%;
animation-range: 25% normal;
animation-range: 25% 50%;
animation-range: entry exit; /* Equivalent to entry 0% exit 100% */
animation-range: cover cover 200px; /* Equivalent to cover 0% cover 200px */
animation-range: entry 10% exit; /* Equivalent to entry 10% exit 100% */
animation-range: 10% exit 90%;
animation-range: entry 10% 90%;

The animation-range shorthand property can be applied to a container element as a combination of the <animation-range-start> and <animation-range-end> values. If both the values are specified, they will be interpreted in the order <animation-range-start> then <animation-range-end>.

As shown by the comments in the syntax block above, if only a single value is provided there are a couple of possible interpretations:

• If the value is a <length-percentage> or normal, <animation-range-start> will take that value, and <animation-range-end> will equal normal.
• If the value is a named timeline range without a <length-percentage> following it, the range will be between that named timeline range at 0% and 100%.
• If the value is a named timeline range with a <length-percentage> following it, the range will start at that named timeline range and percentage, and end at that named timeline range and 100%.

One or two values representing the animation-range-start and/or animation-range-end. These values can be one of the following:

normal

Represents the start of the timeline in the case of animation-range-start and the end of the timeline in the case of animation-range-end. This is the default value.

<length-percentage>

A length or percentage value measured from the beginning of the timeline.

<timeline-range-name>

A specific named timeline range inside the overall timeline. Possible values are:

cover

Represents the full range of a named view progress timeline (see CSS scroll-driven animations for more details), from the point where the subject element first starts to enter the scroll port's view progress visibility range (0% progress) to the point where it has completely left it (100% progress).

contain

Represents the range of a named view progress timeline where the subject element is fully contained by, or fully contains, the scroll port's view progress visibility range.

• If the subject element is smaller than the scrollport, it ranges from the point where the subject element is first completely contained by the scroll port (0% progress), to the point where it is no longer completely contained by the scroll port (100% progress).
• If the subject element is larger than the scrollport, it ranges from the point where the subject element first completely covers the scroll port (0% progress), to the point where it no longer completely covers the scroll port (100% progress).

entry

Represents the range of a named view progress timeline from the point where the subject element first starts to enter the scroll port (0% progress), to the point where it has completely entered the scroll port (100%).

exit

Represents the range of a named view progress timeline from the point where the subject element first starts to exit the scroll port (0% progress), to the point where it has completely exited the scroll port (100%).

entry-crossing

Represents the range of a named view progress timeline from the point where the subject element first starts to cross the scroll port's starting edge (0% progress), to the point where it has completely crossed the scroll port's starting edge (100%).

exit-crossing

Represents the range of a named view progress timeline from the point where the subject element first starts to cross the scroll port's end edge (0% progress), to the point where it has completely crossed the scroll port's end edge (100%).

In the case of <timeline-range-name> values that do not include a <length-percentage>, the percentage defaults to 0% if it is an animation-range-start value, and 100% if it is an animation-range-end value.

Note: It is quite hard to visualize what these values mean from the descriptions above. Fortunately, the View Timeline Ranges Visualizer shows exactly what they mean in an easy visual format.

<timeline-range-name> <length-percentage>

A combination value that equals the specified percentage or distance through the specified named timeline range, measured from the start of that timeline range.

animation-range = 
  [ <'animation-range-start'> <'animation-range-end'>? ]#  

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

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

<length-percentage> = 
  <length>      |
  <percentage>  

See the View Timeline Ranges Visualizer for a nice easy visual explanation of what all the value types mean.

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 declaration is also set to make the animation begin later than expected, and finish earlier.

HTML

The HTML for the example is shown below.

<div class="content">
  <h1>Content</h1>

  <p>
    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.
  </p>

  <p>
    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.
  </p>

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

  <p>
    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.
  </p>
</div>

CSS

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;
}

p,
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 declaration to make the animation begin later than expected, and finish earlier.

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: entry 10% contain 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);
  }
}

Result

Scroll to see the subject element being animated.

• animation-timeline
• animation-range-end, animation-range-start
• scroll-timeline, scroll-timeline-axis, scroll-timeline-name
• timeline-scope
• view-timeline-inset
• CSS scroll-driven animations