I recently noticed that animations in Safari were stuttering pretty badly on my M1 powered 2020 MacBook Air, and dove in to figure out why.
This wasn’t a bug. This was a feature.
By default, macOS Monterey enables “Low power mode” on Battery power and disables it when using a Power Adapter. Safari, it seems, is programmed to interpret this setting to mean that it should reduce the number of times it paints to the screen to prolong battery life.
On my MacBook Air, that means from 60fps to 30fps.