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This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The KeyframeEffectOptions dictionary, part of the Web Animations API, is used by Element.animate(), KeyframeEffectReadOnly() and KeyframeEffect() to describe timing properties for animation effects. These properties are all optional, although without setting a duration the animation will not play.

In other words, these properties describe how the user agent should go about making the transition from keyframe to keyframe, and how to behave when the animation begins and ends.


composite This is an experimental API that should not be used in production code. Optional
Determines how values are combined between this animation and other, separate animations that do not specify their own specific composite operation. Defaults to replace.
  • add dictates an additive effect, where each successive iteration builds on the last. For instance with transform, a translateX(-200px) would not override an earlier rotate(20deg) value but result in translateX(-200px) rotate(20deg).
  • accumulate is similar but a little smarter: blur(2) and blur(5) become blur(7), not blur(2) blur(5).
  • replace overwrites the previous value with the new one.
iterationComposite This is an experimental API that should not be used in production code. Optional
Determines how values build from iteration to iteration in this animation. Can be set to accumulate or replace (see above). Defaults to replace.
pseudoElement This is an experimental API that should not be used in production code. Optional
The selector of the pseudo-element to be targeted, if any. Defaults to null.
delay Optional
The number of milliseconds to delay the start of the animation. Defaults to 0.
direction Optional
Whether the animation runs forwards (normal), backwards (reverse), switches direction after each iteration (alternate), or runs backwards and switches direction after each iteration (alternate-reverse). Defaults to "normal".
duration Optional
The number of milliseconds each iteration of the animation takes to complete. Defaults to 0. Although this is technically optional, keep in mind that your animation will not run if this value is 0.
easing Optional
The rate of the animation's change over time. Accepts the pre-defined values "linear", "ease", "ease-in", "ease-out", and "ease-in-out", or a custom "cubic-bezier" value like "cubic-bezier(0.42, 0, 0.58, 1)". Defaults to "linear".
endDelay Optional
The number of milliseconds to delay after the end of an animation. This is primarily of use when sequencing animations based on the end time of another animation. Defaults to 0. 
fill Optional
Dictates whether the animation's effects should be reflected by the element(s) prior to playing ("backwards"), retained after the animation has completed playing ("forwards"), or both. Defaults to "none".
iterationStart Optional
Describes at what point in the iteration the animation should start. 0.5 would indicate starting halfway through the first iteration for example, and with this value set, an animation with 2 iterations would end halfway through a third iteration. Defaults to 0.0.
iterations Optional
The number of times the animation should repeat. Defaults to 1, and can also take a value of Infinity to make it repeat for as long as the element exists.


See also