How to test a monitor for stuck subpixels

A tiny red, green, or blue dot that stays visible on your monitor can be distracting, especially on a plain background. It may be a stuck subpixel, but dirt, an image artifact, or a graphics problem can look similar.

Use solid color fields to see whether the mark stays in the same place and changes as expected. The Display Test can show colors for checking your screen. This test helps you narrow down the cause, but it cannot repair a physical panel defect.

Test for a stuck subpixel

1. Open the Display Test on the monitor you want to check. If you have more than one screen, make sure the test is on the monitor with the suspected dot.
2. Use the test's color patterns to display a plain, solid color. Look closely at the suspected spot without pressing on the screen.
3. Check several colors, including white, black, red, green, and blue, if available. A stuck subpixel may stand out on one background and blend in on another.
4. Look at the spot from your normal viewing position, then move a little closer. Note whether it stays in exactly the same physical place on the panel.

Clean the screen gently if there is a mark on its surface, then repeat the check. Do not rub or press on the panel to try to change the dot. Pressure can damage the display or create more marks.

What the result means

A red, green, or blue dot stays in one place

This is consistent with a subpixel that is stuck on. Each pixel is made up of red, green, and blue subpixels. If one component stays lit when the image changes, it can look like a tiny colored dot. A browser test cannot confirm the panel electronics are at fault, so check the steps below before deciding.

A dark spot stays in one place

A dark spot may be a subpixel that is not lighting, rather than one stuck on. It might be a dead pixel, but a single dark component can be hard to distinguish from a stuck pixel on some backgrounds. See stuck pixel vs. dead pixel for the difference.

The mark changes or disappears when the color changes

That can be normal. A functioning subpixel changes brightness with the color being displayed, and a faint mark may only be visible against a particular shade. If it vanishes on some fields, compare the same fields again and check whether the point remains fixed in the same panel location.

The mark moves with the image or appears in a screenshot

If it moves when you move a window, scroll, or change the image, it is more likely part of the picture or an application effect than a panel defect. To check a screenshot, view it on another screen or device. A physical screen defect will not be saved into the screenshot, though you may still see the spot while viewing it on the affected monitor.

How to rule out other problems

1. Clean the screen gently. Turn the monitor off and use a clean, soft microfiber cloth. Wipe lightly, following the monitor maker's cleaning instructions. A speck on the surface can resemble a subpixel, but do not use a sharp tool or apply pressure.
2. Check another image or app. Show the same solid colors in a different image or application. If the mark appears only in one file or window, the issue may be in that content rather than the monitor.
3. View the same test on another screen. If the dot appears in the same part of the test image on another display, check the image or browser. If it stays at one physical point on the original monitor, the panel becomes more likely.
4. Reconnect an external monitor. Unplug and reconnect the display cable at both ends, or try another input or cable. If practical, connect the monitor to a different computer. A mark that stays fixed on the same panel across sources points toward the monitor itself.
5. Check the display resolution. Use the recommended resolution for the monitor. In Windows 11, open Settings › System › Display and check Display resolution. In macOS, open System Settings › Displays and select the recommended or default resolution. This will not unstick a subpixel, but it can rule out an unusual display mode.
6. Restart the computer and test again. A restart can clear a temporary graphics or browser issue. If the dot remains fixed on the physical screen after the restart, compare it with a second device or input before seeking support.

When it is a panel defect

A dot that stays in the same physical location across different colors, applications, cables, and devices is strong evidence of a panel issue. Take a photo that shows the mark against a plain background, and keep a note of which colors make it easiest to see. Check the monitor's warranty terms before attempting any repair. Dead or stuck subpixels usually need manufacturer service or panel replacement, and a screen test cannot guarantee that a manufacturer will accept a warranty claim.

Why the dot changes color

A pixel is a group of tiny red, green, and blue light-producing elements. A stuck subpixel that remains lit can look red on a dark field, blend into a red field, or appear as a different tint when other colors are shown. A subpixel that does not light may look like a dark point. That is why checking one background alone can give a misleading result.

Flashing color patterns are not required to identify a fixed spot. If you are considering them, read what to check before trying flashing pixel patterns first.