How to run the screen test
1. Wipe the screen with a dry cloth: dust looks like a dead pixel.
2. Click "Start screen test". The screen turns completely white.
3. Look over the whole screen calmly and up close, including corners and edges. Then move to black and the other colors with the arrow keys, by clicking the sides or by swiping.
4. A dot that stays the same color on every screen is a faulty pixel. Press Esc to exit.
Dead pixel or stuck pixel
A dead pixel is always off: it shows as a black dot on white and other light colors. It is usually a permanent panel defect.
A stuck pixel is always lit in one color (red, green or blue) and shows mostly on black. Sometimes it recovers by itself or with tools that flash colors quickly over that spot, but there is no guarantee.
A dot that moves when you move your head or disappears after cleaning is dirt, not a pixel.
Backlight bleed and blotches
On the black screen, turn off the room lights and look at the edges and corners. Bright patches there are backlight bleed, common on LCD and IPS screens. A little is normal; strong patches that show in dark videos can justify a warranty replacement.
On the gray screen, look for areas lighter or darker than the rest (poor uniformity) and vertical or horizontal bands, which point to a panel or display cable problem.
OLED screens have no backlight, so they have no bleed: black should be completely off.
Worth checking before buying a used laptop
Dead pixels, blotches and backlight bleed are hard to spot on a screen full of windows and icons. Open this test on the seller’s laptop and go through every color: it takes less than a minute. Also check whether the screen flickers when you move the lid, a sign of a worn display cable.
How many dead pixels warranties accept
Each manufacturer has its own pixel defect policy, usually based on the ISO 9241-307 standard. In general, a few faulty pixels are tolerated, and a replacement only happens above a minimum count or when the pixel is in the center of the screen. Photograph the defect during the test and check the manufacturer’s policy before filing a claim.
Frequently asked questions
How do I check my laptop screen for dead pixels?
Click "Start screen test" and look over the whole screen on white and black, then on the other colors. A dot that does not change color on every screen is a faulty pixel.
What is the difference between a dead and a stuck pixel?
A dead pixel is always off (a black dot on light backgrounds). A stuck pixel is always lit in one color, like red or green, and shows on black.
Can a stuck pixel be fixed?
Sometimes. Stuck pixels may recover with tools that flash colors quickly over that spot for a few minutes. Dead pixels almost never come back.
How do I check for backlight bleed?
Use the black screen in a dark room with brightness at maximum. Bright patches at the edges and corners are backlight bleed.
How do I exit the full-screen test?
Press Esc. On a phone or tablet, tap the screen to show the exit button.
Does the screen test work on a phone?
Yes. Swipe to change color. On some iPhones full screen does not fully hide the browser bars, but the test works normally.