Refresh rate

A 60 Hz display draws a new image every 16.7 ms, a 144 Hz one every 6.9 ms. A higher rate shows motion in smaller steps, shortens the wait before a new frame can appear, and halves the smear of a moving edge each time the rate doubles. It only helps if something supplies new frames that often: a game running at 50 fps on a 144 Hz screen still shows 50 new images a second.

The rate also sets part of every reaction time and input delay. A frame begun at the moment something changes appears at the next refresh at the earliest, and the scan reaches the middle of the screen half a refresh later. The reaction time test models that as half to one and a half refresh intervals: 8.3 to 25 ms at 60 Hz, 3.5 to 10.4 ms at 144 Hz.

A display often runs below its rated maximum because the operating system has not been set to it, the cable or port cannot carry it, or a laptop has lowered it on battery. Microsoft and Apple both document where the setting lives. The refresh rate test reads the rate the browser actually delivers frames at, which is what the setting achieved, not what the box promised.