How to Test a Screen for Dead and Stuck Pixels

A new monitor arrives, you plug it in, and three days later you notice a tiny bright green dot in the middle of a dark scene. Now you’re trying to remember whether it was there from the start, and whether the return window closes tomorrow.

Pixel faults are the one hardware defect that hides in plain sight. On a normal desktop full of windows and text, a single wrong pixel is invisible. On a solid colour it’s obvious. That asymmetry is the entire reason a dedicated test exists.

What you’re actually looking for

Three different faults get lumped together, and the distinction affects whether anything can be done.

A dead pixel never lights at all. It shows as a black dot on a white background and disappears completely on black. Dead pixels don’t recover.

A stuck pixel is permanently on in one colour — usually red, green or blue. It’s obvious against black and invisible against a matching background. Stuck pixels sometimes recover on their own or with coaxing.

A dim or hot sub-pixel is a partial fault: one of the three sub-pixels behind a pixel is weak or always on, producing a faint tint rather than a clear dot.

Then there’s dust, which people report as a dead pixel more often than any actual defect. Clean the screen before you conclude anything.

Why people get stuck here

• Testing too late. Manufacturer and retailer policies are time-limited, and a fault found in month four is a very different conversation from one found on day one.
• Testing in a bright room. Ambient light washes out exactly the faint faults you’re looking for.
• Not knowing the threshold. Most panel makers publish a defect policy that allows a certain number of faulty sub-pixels before a panel qualifies for replacement, and the number varies by class of panel.
• Only testing black and white. A pixel stuck on green is invisible on a green background and blatant on magenta. You need the full sequence.

What a good test looks like

Full screen, no chrome

Any browser toolbar or taskbar covering part of the panel is part of the panel you haven’t tested. Faults cluster near edges as often as in the middle.

Every primary, plus black and white

Red, green and blue reveal sub-pixel faults. White reveals dead pixels. Black reveals stuck ones and any backlight bleed around the edges. Greyscale steps help with dim pixels and banding.

Enough time on each colour, in a dark room

Five seconds per colour, lights off, eyes given a moment to adjust. Rushing the sequence is how a faint fault gets missed.

Common mistakes to avoid

• Testing before cleaning the screen, then reporting dust as a defect.
• Pressing hard on the panel to “fix” a stuck pixel — pressure can create permanent damage far worse than the original fault.
• Running the test in daylight and concluding the panel is perfect.
• Forgetting to check the corners and edges, where backlight bleed lives.
• Leaving the test until after you’ve removed the packaging and thrown away the receipt.

How to do it with Dead Pixel Test

The Dead Pixel Test cycles full-screen colours with no download and nothing to install.

1. Clean the screen properly with a dry microfibre cloth first.
2. Turn the room lights down and set brightness to a normal working level.
3. Start the colour sequence full screen and let each colour hold for several seconds.
4. Scan systematically — corners, edges, then the middle — rather than staring at the centre.
5. Photograph any fault you find, with the colour on screen, before contacting the retailer.

Other quick device checks are in the tools directory, all of them browser-only.

Frequently asked questions

Can a stuck pixel be fixed?

Sometimes. Rapidly cycling colours over the affected area for several minutes occasionally frees a stuck sub-pixel. Gentle, very light pressure while the screen redraws is the other folk remedy — and it carries a real risk of making things worse, so it’s a last resort on a panel you can’t return.

How many bad pixels does a warranty allow?

It depends on the manufacturer and the panel class. The ISO 9241-307 standard defines pixel fault classes that many makers reference, and most consumer panels are sold under a class that tolerates a small number of sub-pixel faults. Check your specific model’s policy — and test early, while you still have options.

Does this work on a phone or TV?

Yes, as long as you can open a browser full screen on it. OLED panels are worth testing too, though their failure modes lean toward uneven ageing rather than individually stuck pixels.

Final thought

Run the test in the first hour, not the first month. Five minutes with a dark room and a colour cycle is the difference between a straightforward replacement and an argument about when the fault appeared.

Try the free Dead Pixel Test