diagnostic · one of 29free, no counter
Animation
What is animating on this page, and what is it costing?
An animation on `transform` or `opacity` runs on the compositor and costs almost nothing; the same animation on `top` or `width` re-lays-out the page every frame. Both look identical in the source and completely different on a mid-range phone. This lists what is running right now and which side of that line each one is on.
Reach itPress ⌘+K on any tab and type animation.Ctrl+Kon Windows and Linux
TWO BUILDS9 browsers
Chromelisting in reviewFirefoxlisting in reviewBravelisting in reviewOperalisting in reviewEdgelisting in review4 moreChromium browsers: Arc, Vivaldi, Chromium, Opera GXthe Chrome buildin the panel · free, no counter
What this actually is
every running animation and what it costs per frameOn a page that stutters, on a battery complaint, and on any site with a decorative animation that never ends - an infinite animation on a non-composited property is a page that never stops working.
Asked about this diagnostic
4 of themWhat makes an animation composited?
It drives `transform`, `opacity`, `filter` or a handful of others that the compositor can apply without re-running layout. Anything driving a geometric property costs a layout pass per frame.
Why does it single out infinite animations?
Because they never stop. A two-hundred-millisecond layout-triggering transition is a cost you pay once; the same properties on an infinite loop is a page that keeps a core busy for as long as the tab is open.
Does it show animations that have not started?
No - it lists what is running when you read. A declared animation waiting on a scroll trigger is not costing anything yet, and reporting it as running would be wrong.
How does reduced motion come into it?
A page that animates regardless of `prefers-reduced-motion` is reported here and in Preferences. This one says what is running; that one says what the page was asked for.
TWO BUILDS9 browsers
Chromelisting in reviewFirefoxlisting in reviewBravelisting in reviewOperalisting in reviewEdgelisting in review4 moreChromium browsers: Arc, Vivaldi, Chromium, Opera GXthe Chrome build63 of these · no host permissions · three free audits