Set your display to its native resolution for the sharpest result. Start the test, then use the arrow keys or the buttons to cycle patterns. Press Escape to exit.
Refresh rate
ready
...
Hz measured
...
median interval ms
...
skipped frames
...
intervals timed
This is the rate the browser gets from your system, which is what animation and video on web pages get. Games can run differently.
Background tabs get few or no frames, so keep this tab in front. With two monitors, the monitor this window is on sets the pace.
Battery saver and browser energy saving modes can cap the rate below what the display can do, and some browsers keep pages near 60 frames per second on high refresh screens (Safari has done this on 120 Hz ProMotion displays).
Variable refresh rate (G-Sync, FreeSync, Adaptive-Sync) does not show up here: a browser window normally runs at one fixed rate, usually the highest the display is set to.
Nothing on screen moves or flashes during the measurement; it only times the frames the browser draws.