Frontend & browser·Performance and Core Web Vitals
you have about ten milliseconds of your own work per frame before the animation starts dropping.
Frame budget
Also called16ms budget, frame deadline
The time available per frame at the display's refresh rate — roughly 16.7 milliseconds at 60Hz, 8.3 at 120Hz — shared between your script, style, layout, paint and composite. The browser's own work takes a meaningful slice, so the practical budget for application code is smaller than the headline number. Anything not finishable inside it belongs in a worker, spread across frames, or on the compositor.