The name causes a lot of confusion. A moving ball test does not measure input lag; it cannot, because no input is involved. It checks how smoothly your browser, graphics and monitor deliver frames. The ball moves a fixed distance every frame, so when every frame arrives on time the motion looks perfectly even. When a frame arrives late or is skipped, the ball jumps.
That gives you two things to watch, and they point to different causes.
A stutter every few seconds is a timing problem: a frame missed its slot. On a healthy system that usually comes from something competing for the computer, such as another tab, an extension, a background app or launcher waking up, or a second monitor running at a different refresh rate. Monitors rarely cause rhythmic stutter on their own.
Smearing or a ghost trail behind the ball is the monitor. That is pixel response time, how quickly each pixel changes colour. The overdrive setting in the monitor's menu controls it, and too much overdrive causes a bright halo instead of a trail.
For stutter every few seconds, start with the browser and background software. If the test shows a frame time graph, a steady line with occasional spikes confirms dropped frames. Also confirm Windows really is running the monitor at 144 Hz, because motion tuned for 144 shown at 60 looks uneven.
