css properties animation-composition

The animation-composition CSS property specifies the composite operation to use when multiple animations affect the same property simultaneously.

Syntax

/* Single animation */
animation-composition: replace;
animation-composition: add;
animation-composition: accumulate;

/* Multiple animations */
animation-composition: replace, add;
animation-composition: add, accumulate;
animation-composition: replace, add, accumulate;

/* Global values */
animation-composition: inherit;
animation-composition: initial;
animation-composition: revert;
animation-composition: revert-layer;
animation-composition: unset;

Note: When you specify multiple comma-separated values on an animation-* property, they will be applied to the animations in the order in which the animation-names appear. If the number of animations and compositions differ, the values listed in the animation-composition property will cycle from the first to the last animation-name, looping until all the animations have an assigned animation-composition value. For more information, see Setting multiple animation property values.

Values

replace

The effect value overrides the underlying value of the property. This is the default value.

add

The effect value builds on the underlying value of the property. This operation produces an additive effect. For animation types where the addition operation is not commutative, the order of the operands is the underlying value followed by the effect value.

accumulate

The effect and underlying values are combined. For animation types where the addition operation is not commutative, the order of the operands is the underlying value followed by the effect value.

Description

Each property that is targeted by the @keyframes at-rule is associated with an effect stack. The value of the effect stack is calculated by combining the underlying value of a property in a CSS style rule with the effect value of that property in the keyframe. The animation-composition property helps to specify how to combine the underlying value with the effect value.

For example, in the CSS below, blur(5px) is the underlying value, and blur(10px) is the effect value. The animation-composition property specifies the operation to perform to produce the final effect value after compositing the effect of the underlying value and the effect value.

.icon:hover {
  filter: blur(5px);
  animation: 3s infinite pulse;
  animation-composition: add;
}

@keyframes pulse {
  0% {
    filter: blur(10px);
  }
  100% {
    filter: blur(20px);
  }
}

Consider different values for the animation-composition property in the above example. The final effect value in each of those cases will be calculated as explained below:

Note: A composite operation can also be specified in a keyframe. In that case, the specified composite operation is used for each property first within that keyframe and then on each property in the next keyframe.

Formal definition

Initial valuereplace
Applies toall elements
Inheritedno
Computed valuelist, each item a keyword as specified
Animation typenot animatable

Formal syntax

<single-animation-composition>#

Examples

Understanding the animation-composition values

The example below shows the effect of different animation-composition values side-by-side.

HTML

<div class="container">
  replace
  <div id="replace" class="target"></div>
</div>
<div class="container">
  add
  <div id="add" class="target"></div>
</div>
<div class="container">
  accumulate
  <div id="accumulate" class="target"></div>
</div>

CSS

Here the underlying value is translateX(50px) rotate(45deg).

@keyframes slide {
  20%,
  40% {
    transform: translateX(100px);
    background: yellow;
  }
  80%,
  100% {
    transform: translateX(150px);
    background: orange;
  }
}

.target {
  transform: translateX(30px) rotate(45deg);
  animation: slide 5s linear infinite;
}
.target:hover {
  animation-play-state: paused;
}
#replace {
  animation-composition: replace;
}
#add {
  animation-composition: add;
}
#accumulate {
  animation-composition: accumulate;
}

Result

See also