AnimationEffect

Web animations web-animations

Baseline: Widely available on the web, in every major browser since Sep 2020, and long enough to count on (since Mar 2023).

niso: Partial 91%. 3301 of 3589 subtests pass, by system: Linux 91%, macOS 91%. Engines: QuickJS, the engine niso's WPT run uses; Node and Porffor have no recorded run. WPT results recorded at f3b4fa8, 2026-11-10; web-features 3.45.0. WPT tests · niso's support · Animation, AnimationEffect, AnimationPlaybackEvent, AnimationTimeline

AnimationEffect is an interface in idl/web-animations.webidl, exposed in Window. What it does is on MDN; this page says what niso has of it.

Timings cross as strings: timing() and computedTiming() list the EffectTiming members in IDL order, then endTime, activeDuration, localTime, progress and currentIteration, “” for null; update() takes name, value pairs for the members present.

Status

The web features its members belong to, each with its Baseline status on the web and how much of the feature’s WPT suite passes in niso (see Web platform support).

Feature	On the web	In niso	Members
Web animations	Widely available	Partial 91% 3301 of 3589 subtests pass	4

Members

getTiming()

operation

[NisoGlue] EffectTiming getTiming();

getComputedTiming()

operation

[NisoGlue] ComputedEffectTiming getComputedTiming();

updateTiming()

operation

[NisoGlue] undefined updateTiming(optional OptionalEffectTiming timing = {});

timing()

operation not in JS

[NisoInternal] sequence<DOMString> timing();

int32_t niso_animation_effect_timing(niso_dom* dom, niso_handle self, niso_strs* out);

computedTiming()

operation not in JS

[NisoInternal] sequence<DOMString> computedTiming();

int32_t niso_animation_effect_computed_timing(niso_dom* dom, niso_handle self, niso_strs* out);

update()

operation not in JS

[NisoInternal] undefined update(sequence<DOMString> timing);

int32_t niso_animation_effect_update(niso_dom* dom, niso_handle self, const niso_str* timing, size_t timing_len);