Ghosting test
A trail behind a moving object is not one fault. It is either a pixel that has not finished changing colour, or an overdrive circuit pushing it too far — and the two are fixed by turning the same setting in opposite directions. This runs the same moving block across fifteen different grey transitions so you can see which ones your panel is slow at, and which kind of trail you have.
The test opens full screen. Space — next · Arrow keys — back and forward · Esc — exit
Your browser blocked full screen. The test still works in this window, but a full-screen view is more reliable — try pressing F11.
Did any lane leave a visible trail behind the block?
Running the test
Space cycles the speed, from 480 to 1920 pixels per second. Up and down change the set of transitions. Esc exits.
Each lane is one transition, labelled with the two values involved. The background is the first number, the moving block is the second, so the leading and trailing edges of the block drive that pixel change in both directions.
Watch the trailing edge — the side the block has just left. That is where an unfinished transition shows.
The three sets
Across the range puts a full black-to-white change at the top and four smaller steps below it. The top lane is the control: it is the transition every panel is fastest at, so whatever it looks like is your panel’s best case, and the lanes below are read against it.
Dark transitions are five small steps near black. This is the set that matters, and it is the one a white-bar-on-black test cannot show you at all. VA panels are slow here — often slow enough that a dark object leaves a visible smear across a dark background — while IPS and TN panels usually stay clean. If the range set looked fine and this one does not, you have a VA panel behaving normally rather than a monitor with a fault.
Overshoot check alternates rising and falling transitions down the screen. Overdrive works hardest on large steps, and a corona shows up as a trail brighter than the background it crosses. Having a light-on-dark lane directly above a dark-on-light one makes it unmistakable.
What a trail actually is
A liquid crystal pixel does not switch. It rotates, and rotation takes time. At 60 Hz a pixel has 16.7 ms to reach its new value; at 144 Hz it has 6.9 ms. If it has not arrived when the next frame is drawn, the object appears to drag a faint copy of itself behind it — the pixels behind it are still on their way.
Overdrive is the manufacturer’s answer: aim past the target so the pixel gets there faster, then correct. Set too weak, the pixel arrives late and you see ghosting. Set too strong, it overshoots past the target and has to come back, and you see a bright or inverted halo. The setting is a single dial with a fault at each end, and finding the middle is what this test is for.
Windows 11
- Overdrive is a monitor setting, not a Windows one. It lives in the physical menu on the monitor, under Overdrive, Response Time, OD, Trace Free, AMA or MPRT depending on the maker. Nothing in Windows changes it.
- Variable refresh rate interacts with it. With FreeSync or G-Sync active the refresh rate moves continuously, and a monitor with a single fixed overdrive level will be tuned correctly for only part of that range. Monitors that advertise variable overdrive adjust it as the rate changes; most do not. If ghosting appears only in games, try the test with variable refresh off.
- If the monitor has an MPRT or backlight strobing mode, it is not an overdrive setting. It reduces persistence blur by turning the backlight off between frames, at the cost of brightness, and it usually cannot run at the same time as variable refresh.
macOS
- macOS exposes no overdrive control at all, on any display. If an external monitor ghosts, the setting is in the monitor’s own menu.
- Apple’s own panels are IPS or OLED and are not prone to the dark-transition smearing this test looks for. An OLED has no liquid crystal to rotate and effectively no ghosting; any trail you see on one is persistence.
- On an external monitor over USB-C or Thunderbolt, check the refresh rate in System Settings → Displays first. A display running at 60 Hz when it could run at 120 will look worse here for reasons that have nothing to do with response time.
When it is not the monitor
A trail that appears only in one application, or only over video, is not this. Video players and streaming services apply their own motion processing, and compression itself smears fast movement. Test the panel with this page, and if the panel is clean, the smearing is in the content or the decoder rather than the display.
Common questions
What is the difference between ghosting and motion blur?
Ghosting is a fault in how fast a pixel can change from one colour to another, and it affects some colour pairs much more than others. Motion blur is not a fault at all — it happens because each frame is held on screen for the whole refresh interval while your eye keeps moving, so the still image smears across your retina. Every sample-and-hold display has it and no monitor setting removes it. Ghosting leaves a trail that follows the object; persistence blur softens the whole object evenly. If only some of the lanes here trail, it is ghosting. If all of them look equally soft, that is persistence.
Why does the black-to-white lane look fine when the dark lanes smear?
Because the size of the voltage step is not what makes a transition slow. Liquid crystal moves fastest when it is driven hard, which is what a full black-to-white change does, and slowest on small steps near black where the drive voltage is tiny. This is why a panel can look perfectly sharp in a bright game and smear badly in a dark one, and it is the single most common complaint about VA monitors.
How do I tell ghosting from overshoot?
By the brightness of the trail relative to what it is crossing. Ghosting trails are always between the two colours involved — a faint copy of the block, fading. Overshoot trails go past the background: a bright halo behind a dark block, or a dark shadow behind a bright one. If you see something brighter than the background behind a moving object, that is not the pixel being slow, it is the panel driving it too far and having to come back. The overshoot set puts a rising and a falling transition next to each other so the difference is side by side.
Which overdrive setting should I choose?
The strongest level that does not produce a visible halo. Run the overshoot set at the fastest speed, open the monitor menu, and step through the overdrive levels one at a time — they are usually called Overdrive, Response Time, Trace Free or OD depending on the maker. Watch the trails: as you increase the setting they get shorter, and at some point a bright edge appears behind the dark block. Go back one level. That is your setting, and on most monitors it is the middle option rather than the strongest.
My laptop has no overdrive setting. Is there anything to do?
Not for the ghosting itself. Laptop panels almost never expose the setting, and the panel behaves how it behaves. What is worth checking is that the display is actually running at its highest refresh rate and that battery saving has not dropped it, because that reduces the persistence blur sitting on top of the ghosting. The refresh rate test measures what you are really getting.
Is a browser test good enough to judge this?
For seeing which transitions trail and for comparing overdrive settings against each other, yes — these are visible artefacts and your eye is the right instrument. For a response time in milliseconds, no. That needs a photodiode and an oscilloscope pointed at the panel, and any web page claiming to produce that number is producing something else.
Does the refresh rate change what I see here?
Yes, and it is worth knowing which way. A higher refresh rate gives each pixel less time to finish its transition, so the same panel shows more ghosting at 144 Hz than at 60 Hz. Monitors compensate by increasing overdrive at higher refresh rates, and some do it badly — which is why a monitor can be clean at 144 Hz and show overshoot at 60 Hz, or the reverse. If you use more than one refresh rate, check the overdrive setting at each.