Monitor Test: Dead Pixel and Ghosting Test
Fill the screen with one color to find dead or stuck pixels and backlight bleed, then watch a moving shape for ghosting. It runs in your browser with nothing to install, so check a new monitor before the return window closes.
Dead pixel test
The screen fills with black, white, red, green, blue and gray in turn. On each color, look closely for a tiny dot that doesn't match.
The whole screen changes color. If you are sensitive to light, lower the brightness first. Colors change only when you press a key or click, never on their own.
Next color: →, Space or click. Previous: ←. Exit: Esc.
Color order (click one to start from it)
Next: → or click the screen. Previous: ←. Exit: Esc
Ghosting test
A shape crosses the screen at a steady speed, the same idea as the 'UFO test'. Follow it with your eyes and look for a blurry trail or a bright outline.
- Browser refresh
- about - Hz
- Distance per frame
- - px
The shape moves only after you press Start and never flashes. Clicking the lane also starts or pauses it.
The browser isn't drawing often enough to measure the refresh rate. Turn off power saving or bring this window to the front, then press Pause and Start again.
Your browser is drawing at 75Hz or less. If you have a high refresh rate monitor, first check that it isn't set to 60Hz. Monitor Refresh Rate Test
Paused because you left this tab. Press Start to move it again and re-measure the refresh rate.
Monitor Refresh Rate Test FPS Drop and Stutter Cause Checker PC Bottleneck Check
How to run a dead pixel test
- Wipe the screen with a soft cloth to remove dust first.
- Press 'Start full screen' so no window frame or taskbar hides the edges.
- Scan each color edge to edge: bright dots on black, dark dots on white, off-color dots on red, green and blue.
- If you spot one, keep that color on screen and take a close photo that shows where it is.
Types of bad pixels
- Bright pixel
- A pixel stuck on, so it glows white or one color on a black screen. It stands out in dark scenes.
- Dead pixel
- A pixel that doesn't light up, so it shows as a black dot on white or other bright screens.
- Stuck pixel
- Some of the red, green or blue subpixels that make up a pixel are stuck on or off, so the dot shows a different color on solid red, green or blue.
Telling dust from a bad pixel
- If it moves or disappears when you change your viewing angle or wipe the screen with a soft cloth, it is dust on the surface.
- A bad pixel is a sharp, one-pixel dot that stays put on every color; dust has soft edges.
- If you find one, take a close photo that shows where it is. You will need it to ask for a replacement.
Checking backlight bleed on a black screen
On a black screen, a cloudy glow at an edge or corner can be backlight bleed. Don't check in a dark room; look straight at it in a normally lit room.
- If the glow changes with viewing angle or distance, it is IPS glow, a trait of IPS panels and not a defect.
- If it stays the same at every angle, it is light leakage, which can count as a defect when it seriously affects viewing.
- OLED screens have no backlight, so they don't bleed.
Found a bad pixel? Check the replacement rules
How many bad pixels qualify for replacement differs by maker, model and seller, and some set separate limits for bright and dead pixels. Note how many of each and where, then check the pixel policy in your warranty and the seller's return period.
How to read the ghosting test: ghosting and overshoot
- A blurry trail behind the shape is ghosting (motion blur), caused by pixel response time and how the screen holds each frame.
- An outline in the opposite color is inverse ghosting; try one step lower on the monitor's response time (overdrive) setting.
- A higher refresh rate means less movement per frame, so less smear (see 'distance per frame' above).
- If the shape stutters, the browser is dropping frames, not ghosting; close other programs and try again.
Bad ghosting? Check the Windows refresh rate first
Lutimize (our app) uses 'Set Maximum Refresh Rate' to run your monitor at its highest supported rate. It can't fix bad pixels or the panel's response time.
What this test can't tell you
- It can't measure numbers like response time (ms). It is a visual check.
- The browser refresh is for the monitor the window is on, and power saving or other work can make it read low.
- Browsers without full screen, such as on iPhone, only fill the window, so areas under the address bar aren't checked.
- Test values are not sent to our server or kept in the address. The site's general usage statistics collect ordinary visit information separately.
Common questions
Will a single bad pixel get my monitor replaced?
It depends on the maker, model and seller, so the count alone doesn't answer it. Check the warranty terms or ask support, with a photo showing where it is.
Can a stuck pixel fixer repair a bad pixel?
This tool only finds bad pixels; it doesn't fix them. We found no official evidence that screen-flashing fixers work, and rapid flashing can be dangerous for people sensitive to light.
Does this test show an old image that stays on screen?
No. A faint copy of a long-displayed static image is burn-in (image retention), a different problem from the motion smear this test shows.
Is this the same as the UFO test?
It works the same way: you follow a moving object to see ghosting. Here you can also pick the speed and background.
Can I run a dead pixel test on an OLED monitor?
Yes, the method is the same. OLED has no backlight, so there is no bleed to check.
Can I test a laptop or phone screen?
Yes. On a phone, tap to go to the next color and use the X in the brief hint to exit.
Are my results saved?
No. Test values are not saved or sent to our server; the site's general usage statistics collect ordinary visit information separately.
Last reviewed 2026-11-08