How to use the monitor dead pixel test
- Wipe dust and fingerprints off the screen with a soft cloth. Mistaking dust for a dead pixel is the most common error.
- Set the brightness to the level you normally use, and darken the room if you want to check for backlight bleed.
- Press “Dead pixel test” to go full screen and step through solid black, white, red, green, blue and more. Press the space bar or click to move on.
- On each color, look closely at the screen and scan every corner for a dot that looks different from its surroundings.
- Press Esc when you are done. On a phone, tap the screen to advance. In browsers that cannot go full screen, the test covers the whole page instead.
What is a defective pixel?
A screen builds its picture from tiny dots called pixels, and each pixel is made of three sub-pixels: red, green and blue. When part of one stops working properly it becomes a defective pixel. They are usually sorted into bright dots that are always on, dark dots that are always off, and colored dots where a single sub-pixel is stuck on or off.
Solid colors are used because they make the problem stand out. A stuck bright dot shows on black, a dark dot shows on white, and a faulty sub-pixel shows clearly on red, green or blue. Dust and scratches disappear when you wipe the screen or seem to move as you change your viewing angle, but a defective pixel stays in exactly the same place.
Panel types compared: IPS, VA, TN and OLED
- IPS: colors hold up well from wide angles and color accuracy is good. Blacks look a little brighter, and in a dark room the corners can glow when you look from an angle.
- VA: high contrast and deep blacks. Some models show smearing behind moving objects in dark scenes, and viewing angles are narrower than IPS.
- TN: fast response and low prices, but narrow viewing angles and weaker color.
- OLED: each pixel makes its own light, so there is no backlight and no backlight bleed, and black is truly off. Leaving a static image on screen for a long time can cause burn-in.
Each panel has different weak spots, so what you look for changes. On IPS and VA, use black and dark gray screens to check for backlight bleed and uneven patches. On any panel, use solid colors to look for defective pixels.
Replacement and refund standards for defective pixels
How many defective pixels are acceptable depends on the manufacturer and the seller. The international standard ISO 9241-307 divides defects into three types, bright dots, dark dots and sub-pixel faults, and sets a maximum count per million pixels for each class, and many makers refer to it. Published figures differ depending on the edition of the standard and how a manufacturer applies it, so this page does not quote specific numbers. Please check the manual and the manufacturer’s pixel policy for the real limits.
- Test right after you buy, and if you find a problem, keep a photo or video of the solid-color screen that shows where it is.
- If you bought online, check the seller’s return and exchange period and conditions first. They vary by seller and by local law.
- Backlight bleed and mild unevenness are often treated as normal product characteristics and excluded from exchanges, so ask what range is accepted.
Ghosting and response time: what this tool can show
The ghosting test lets you see by eye whether a faint trail follows moving squares and text. If you change the speed, you can compare how much edges blur during fast movement. It is not measuring equipment that can read response time in milliseconds, so it cannot be used to compare against a spec sheet. The refresh rate shown is an estimate from how often the browser draws frames and may differ from the real value. Switching the response time (overdrive) setting in your monitor menu and watching again is a good way to see what that setting changes.
Tips
- Test a new monitor, laptop, tablet or phone on the day you open it. Not missing the return window matters most.
- With a used device, check black, white and all three primary colors as soon as it arrives or at the handover.
- For backlight bleed, darken the room and look from a little distance, straight on.
- If the color bands in the gradient test look like stairs, also check your monitor’s color depth setting, the cable and the graphics settings.
Notes
Looking at bright solid colors up close for a long time can tire your eyes, so check briefly and take breaks. Avoid leaving the same color on an OLED screen for long. This tool is only an aid for spotting flaws by eye and does not decide whether a product passes or whether it qualifies for exchange. We do not offer a “repair” video that flashes the screen rapidly, because it can be uncomfortable or unsafe for some people and is not guaranteed to work.
Frequently asked questions
How can I tell a defective pixel from dust?
If it disappears when you wipe the screen with a soft cloth, it was dust. If it stays in the same spot, it is most likely a defective pixel.
Can a defective pixel be fixed?
A dot that is always off is a hardware fault and is hard for users to fix. Some people report that a stuck colored dot improved, but it is not guaranteed. If the device is under warranty, contact the manufacturer first.
Does it work on phones and tablets?
Yes. Some browsers limit full-screen mode, so the test may cover the page instead and the address bar can remain.
Is backlight bleed a defect?
LCD monitors can have some backlight bleed because of how they are built, and the accepted range differs by manufacturer. Check in a dark room at your normal brightness and compare with the manufacturer’s standard.