Ghosting Test
A white block travels on black. Look for a trail behind it, or a bright or dark edge of the opposite color. The speed is yours to set.
What this test shows
A trail behind a fast object follows how long a pixel takes to change color. An inverse edge, bright or dark, usually means overdrive pushed the pixel too far. They are not the same fault. A smear is slow response. An opposite-color edge is too much overdrive. Raising the speed makes the same panel show the problem larger, which is why a gaming screen and an office screen often separate only on the fast setting.
What the panel adds, and what a setting adds
OLED pixels switch quickly, so the trail is usually lighter. Some VA panels switch slowly between dark shades, so a tail shows even at modest speed. IPS often sits between them. The monitor menu item named overdrive, response time, or acceleration explains an inverse edge better than a new cable does. A wrong cable more often makes motion stutter or caps the refresh rate.
How to compare
Start at a medium speed and see if the edge is clean, then raise the slider. A faint tail only at high speed is common on office screens. A long tail at low speed, or a bright edge at every speed, is a reason to open the monitor menu and drop overdrive one step. Fullscreen removes the rest of the page so the edge is easier to watch. When you also want the hertz readout, use the refresh rate test.
Questions
What is the difference between a trail and an inverse edge?
A trail means the pixel has not finished changing color. An inverse edge means overdrive went too far and left a bright or dark rim. One is a smear. The other is an opposite-color line.
Does a higher speed make the trail easier to see?
Yes. The same response time draws a longer tail when the block moves faster. Clean at low speed and faintly soft at high speed is common. A long tail at low speed is the result worth checking.
Should overdrive be at maximum?
Not always. Overdrive shortens response time, and too much of it paints an inverse edge. Start at normal. If the bright edge is more annoying than the trail, step it down.
How do OLED and LCD differ here?
OLED pixels switch quickly, so the edge is usually cleaner. LCD pixels have to physically reorient, and some VA panels are slow between dark shades. That is a panel trait, not automatically a defect.
Why watch it fullscreen?
Fullscreen removes the toolbar and the rest of the page, so you can watch the edge, and it avoids extra window compositing. Exit fullscreen or press Esc to come back.
Does a trail mean the screen is broken?
Not by itself. A little tail at high speed is common. Change the overdrive step and compare. A bad panel is more likely when the tail is severe at low speed, or only in one region.