the Web Animations surface is identical in a fresh realm
Check id animation-surface-vs-realm
What an ordinary browser yields
The same API surface and the same computed timing values in both realms.
What a detector infers
The Web Animations API exposes a small, precisely specified surface: whether Element.animate exists, whether the timeline and KeyframeEffect constructors are present, and what a created animation reports for its playback rate and computed effect duration. The check drives a real animation in each realm and reads those values back, then requires them to agree. The reason this is worth asking at all is that animation timing is one of the surfaces automation tooling perturbs — either by disabling animations to make pages settle faster, or by driving the clock to skip waits — and doing that in the page world leaves a fresh realm reporting the honest values. Severity is warn rather than critical because the surface is small and a page-level library can legitimately wrap Element.animate.
How to resolve it
If the two realms disagree, something is intervening in animation timing in the page world. Nothing here needs fixing on an ordinary browser.
Read in the wild by
Kasada
Reads the Web Animations surface across seven probes, including a live animation's computed timing.
animation_end_time, animation_playback_rate, animation_duration, animation_progress, animation_play_state, animation_active_duration, animation_overall_progress
Kasada ips.js teardown — the full 427-probe listEvery attribution traces to a published artifact. See the sources and their limits.
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Clearcote is a browser built for fingerprint coherence
It is a Chromium fork, maintained by the same people who wrote this reference. It ships as a compiled browser rather than as a stealth script injected into someone else's — which is a description of how it is built, and is not an argument about how it behaves on this check.
This audit takes no position on how Clearcote scores on Capability surfaces checks, on this one, or anywhere else. It has no baseline corpus of other people's fingerprints to rank you against and no vendor scoreboard — nearly every check is self-referential, asking one browser the same question through two independent APIs and reporting whether both answers can be true at once. It runs identically on any browser, including ours. Run it on yours and read the result yourself.
See the other checks in Capability surfaces — the family animation-surface-vs-realm belongs to.