Blue Screen
A plain blue screen. Go full screen, then press Esc to come back.
Look over the whole screen for dots that stay a different color.
Use your monitor or phone controls to raise the brightness. To come back, press Esc or click Exit full screen.
Ready.
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How to use this test
A full-screen blue page for checking the blue channel of a display and finding stuck pixels. Not the Windows error screen, just a clean blue background.
Press Go full screen and look across the display. Compare with the red and green pages to work out which sub-pixel has failed. Press Esc or click Exit full screen to return.
What the results mean
The blue should be even. A dark dot that is fine on red and green is a dead blue sub-pixel. Blue is the hardest color for the eye to focus on, so look from a normal distance rather than up close.
Common questions
Is this related to the Windows blue screen of death?
No. That's an error message from Windows. This page is just a solid color for testing a display.
Blue looks purple on my screen.
Many displays shift pure blue slightly towards violet, and night-light modes shift it more. It's calibration rather than a defect.
Why does the screen seem dimmer on blue?
The eye is less sensitive to blue than to green, so the same brightness looks darker. That's normal.