Blue Screen Test
Light only the blue subpixel — the dimmest channel, best judged in a dark room.
Only the blue subpixel is lit. Blue is the dimmest channel, so look in a darkened room.
Looking at the whole screen, including the corners — what did you see?
How this test works
The page fills the display with pure blue, lighting only the blue subpixel of every pixel. Blue is the dimmest of the three channels — it contributes least to perceived brightness — so a fault against it is the hardest of the three to spot and the most worth doing in a darkened room with the brightness up. The test reports how much of the panel the fill actually covered and interprets what you report, distinguishing a single dead subpixel from a dead pixel, which are different faults with different warranty treatment.
What the results mean
- Dark dot
- The blue subpixel at that spot is not being driven. The least visible of the three subpixel faults in normal use, because blue contributes least to perceived brightness.
- Even fill
- No visible variation means the blue channel is being driven consistently across the panel.
- Blotches
- Uneven blue across the field is a uniformity characteristic. Blue is where a panel's uniformity problems are often easiest to see.
Common problems and fixes
- The blue looks dim and hard to examine
- That is inherent — blue contributes the least of the three channels to perceived brightness. Turn the room lights down and the display brightness up before judging it.
- I was looking for the Windows blue screen error
- Different thing entirely. This is a solid blue fill for checking a panel; a Windows stop error is a crash screen with an error code on it.
- Blue looks purple or washed out
- Panel colour calibration and any active blue-light filter both shift it. Turn off night mode in your operating system before judging the colour.
Frequently asked questions
Why is blue harder to inspect than red or green?
Because the eye is least sensitive to it. Blue contributes only a small fraction of perceived luminance, so a full blue field looks dim next to a full green one even when the panel is driving it just as hard.
Does this have anything to do with the blue screen of death?
No. That is a Windows crash screen with a stop code. This page just fills your display with blue so you can inspect the blue subpixels.