Press Start. For the next 5 seconds press the Space key as you normally would. The test divides the 5s into 10 × 0.5s bins and reports CPS per bin plus stats (mean, std, CV).
Ready
Each bar = CPS in 0.5s window
Lower CV (%) = more consistent
Tip: Hold the spacebar sometimes triggers key autorepeat — this test counts every keydown event. If you want to test only distinct presses, don't hold; tap repeatedly.