How to test in 3 steps
- 1
Clean the screen and set brightness to maximum
Dust and fingerprints are easily mistaken for dead pixels. Dim the room to make backlight bleed visible.
- 2
Click "Start" to go fullscreen
Use the arrow keys, Space or the mouse to step through each color. Inspect every corner.
- 3
Count anything unusual
Bright dots on black, dark dots on white, off-color dots on red, green or blue. Press Esc to exit.
Reading the results
- A fixed bright dot on black: stuck pixel, usually red, green or blue. Flashing colors for twenty or thirty minutes sometimes unsticks it, but there is no guarantee.
- A black dot on white: dead pixel. Cannot be repaired, only the panel can be replaced. One in a corner may be acceptable; several, or one in the centre, are not.
- Glowing patches at the edges on black: backlight bleed. Mild bleed is normal on IPS panels, heavy bleed is a defect.
- Yellow or pink tint on one side of white or gray: a degraded panel or one that has been pressed or re-glued. Hard to fix.
- Vertical or horizontal lines, flicker: cable or panel fault. Flex the lid to see whether it changes.
- Visible steps in the gradient: 6-bit panel with low color coverage. Not a defect, but unsuitable for graphics work.
Tips for testing a used laptop screen
- Turn off Night Light and any blue-light filter before testing, otherwise white will always look yellow.
- Use 100% brightness to hunt for dead pixels, then drop to 0% on white to check the backlight is even.
- Look at the screen from a 45-degree angle. A TN panel shifts colors dramatically, an IPS panel barely changes. Sellers often advertise IPS when the panel is actually TN.
- After the screen, continue with the keyboard tester and the webcam test.
Frequently asked questions
What is the difference between a dead pixel and a stuck pixel?+
A dead pixel is always dark and shows on a white background. A stuck pixel is always lit in red, green or blue and shows on a black background. Stuck pixels sometimes recover on their own or after flashing colors for a while; dead pixels never do.
Should I buy a laptop with 1 or 2 dead pixels?+
Most manufacturers consider 1–3 dead pixels within spec and will not replace the panel. On a used laptop one small dot in a corner is acceptable if the price is right. A dead pixel in the centre, or three or more, is a reason to negotiate or walk away.
What is backlight bleed?+
Brighter patches along the edges or corners when the screen shows black in a dark room. Almost every IPS panel has a little. It only matters when it is obvious in normal lighting or covers a large area.
The screen looks yellow or pink+
Check on white and gray. If one half of the screen has a different tint from the other, the panel is faulty. If the whole screen is slightly warm, Night Light or a blue-light filter may be on: turn it off in your OS settings and test again.
I see vertical or horizontal lines+
Usually a loose display cable or a failing panel. Open and close the lid a few times on the gray screen: if the lines change with the angle it is the cable, which is far cheaper to fix than the panel.
The gradient shows visible steps. Is that a defect?+
Clear banding from black to white means a 6-bit panel or narrow color coverage. It is not a defect, but such a screen is a poor choice for photo or design work.