The composite property of a KeyframeEffect resolves how an element's animation impacts its underlying property values.

To understand these values, take the example of a keyframeEffect value of blur(2) working on an underlying property value of blur(3).

replace

The keyframeEffect overrides the underlying value it is combined with: blur(2) replaces blur(3).

add

The keyframeEffect is added to the underlying value with which it is combined (aka additive): blur(2) blur(3).

accumulate

The keyframeEffect is accumulated on to the underlying value: blur(5).

• Web Animations API
• Property of KeyframeEffect objects
• Composite operation