RunTheTests
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Ghosting / Motion Blur Test

Move an object at a known speed to see how much your monitor smears behind it.

measuring…

Follow the square with your eyes — what do you see behind it?

Track it, do not stare at a fixed point. Trailing is what your eye sees while following a moving object, which is why a photograph of the screen shows something different.

How this test works

A white square moves across a grey field at a fixed pixels-per-second rate while the page measures your actual refresh rate from frame timing. You track the square with your eyes — not stare at a fixed point, because trailing is what the eye sees while following motion, which is why photographing the screen shows something different. What the tool then reports is the measured refresh rate and the frame hold it implies, and explicitly not a response time in milliseconds. Turning a subjective answer into '8 ms' would be inventing precision of the kind that sells monitors rather than describes them, so the result names pixel response as not measurable and explains what is actually producing the blur.

What the results mean

Frame hold
How long each frame stays on screen: 16.7 ms at 60 Hz, 6.9 ms at 144 Hz. This alone produces blur on any sample-and-hold display.
Slight blur
The expected result. Mostly frame hold rather than the panel, and raising refresh rate reduces it far more than any overdrive setting.
Clear trail
Pixel transitions slow enough to be visible on top of the hold. Characteristic of VA panels on dark transitions in particular.
Pixel response time
Reported as not measurable, because it is. A browser cannot see what the panel does between frames.

Common problems and fixes

Everything smears badly
Check the refresh rate this page measured against what the monitor is rated for. Windows and macOS both default new displays to 60 Hz, and a 144 Hz panel left at 60 smears exactly like this.
There is a bright halo in front of the object, not behind
That is inverse ghosting from overdrive set too high. Turn the monitor's overdrive or Response Time setting down a step — maximum is almost never the right choice.
It looks fine here but bad in games
This runs at a fixed speed in a browser. Games move faster, and frame rate below refresh rate adds stutter that reads as smearing but is a different problem.

Frequently asked questions

Why does this not tell me my response time in milliseconds?

Because a web page cannot measure it. The browser hands frames to the compositor and has no visibility into what the panel does with them. A number here would be derived from which button you pressed, which is not a measurement.

Why is there blur even on a fast monitor?

Sample-and-hold. Each frame is displayed continuously until the next one replaces it, so while your eye tracks a moving object the static frame smears across your retina. This is why 120 Hz looks clearer than 60 Hz even when both panels have identical pixel response.

Should I turn overdrive to maximum?

No. Too much overdrive overshoots the target level and produces inverse ghosting — a bright halo ahead of the object — which is usually more distracting than the trail it removes. The middle setting is right on most monitors.

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