White Screen Test
Fill the screen with pure white to find dead pixels, surface dirt and uneven backlighting.
Every subpixel is driven to full. A pixel that stays dark here is receiving no signal at all.
Looking at the whole screen, including the corners — what did you see?
How this test works
The page fills the display with #ffffff and requests fullscreen, which drives every red, green and blue subpixel to maximum. Against that field, a pixel receiving no signal reads as a dark speck. While fullscreen the test also measures how many device pixels it is actually painting and compares that against the resolution the panel reports, because browser zoom or display scaling can leave strips of screen unlit while the result still looks clean. You then report what you saw, and the tool interprets it — including telling you when what you saw is not a panel fault at all.
What the results mean
- Dark dot
- A pixel dark while everything around it is at full brightness is receiving no signal. That is a dead pixel, and it is permanent.
- Soft smear
- A mark that is visible on white and gone on black is on the outside of the glass. Dust or grease, not a pixel.
- Pixels painted
- Device pixels this fill is actually lighting. If it is smaller than the panel resolution, part of the screen was never tested.
- Uneven brightness
- Variation across a solid white field is a uniformity characteristic of the panel rather than a fault in one pixel.
Common problems and fixes
- The screen will not go fullscreen
- Some embedded and locked-down browser contexts refuse the fullscreen request. The inline fill still works — the coverage figure will tell you how much of the panel it reached, so you know what the result covers.
- I see a mark but cannot tell what it is
- Run the black screen test on the same spot without cleaning anything. A mark on white that vanishes on black is dirt; a fault that appears on both is in the panel.
- Everything looks slightly yellow or blue
- That is the panel's white point, not a fault. Night-shift and blue-light filters in the operating system also shift it — turn those off before judging colour.
Frequently asked questions
Can a white screen test fix a stuck pixel?
No. A static white fill does nothing to a stuck pixel — it needs rapid cycling, which is what a pixel fixer does. A white fill is for finding pixels that are dark, not for repairing ones that are lit.
Why does my screen look dirty only on white?
Because white is the only fill bright enough to show it. Dust and grease scatter light, so they are visible against a bright field and invisible against a black one. That contrast is the test.
Is one dead pixel covered by warranty?
It depends on the manufacturer and often on where the pixel sits — several publish a threshold that treats a centre-screen pixel differently from an edge one. If the device is still inside its return window, exchanging it is usually easier than a warranty claim.