Dead pixel test
Cycle full-screen solid colours (red, green, blue, white, black, grey) to spot dead or stuck pixels: switch colours with a click, the arrow keys or space, leave full screen with Esc, and read the luminance and contrast of each colour.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Solid colour test
Click the swatch or press space / the arrow keys to switch colours, Esc to leave full screen. Full screen in a dim room gives the most reliable check.
Bright stuck pixels show up best on black, dead (dark) pixels on white, red, green and blue. An overall washed-out screen or glow in the corners is backlight bleed, not a dead pixel.
Current colour
What this tool does
- Do an unboxing check on a new monitor or laptop: cycle the solid colours full screen and look for stuck bright pixels, dead dark pixels or blotches.
- Inspect a second-hand device before buying so the number and position of any bad pixels are agreed on the spot.
- Diagnose backlight issues — corner glow on black, uneven brightness or colour shift on white.
- Rule out a rendering problem when a machine freezes and you suspect the GPU or panel is failing.
Example
Input
After entering full screen, press space until the screen shows red #FF0000
Output
Colour Red, hex #FF0000, palette position 1 / 6, relative luminance 0.2126, contrast with white 4.00, contrast with black 5.25
Contrast uses the W3C WCAG 2.1 relative luminance formula, where white on black is 21 and any colour against itself is 1.
Frequently asked questions
What is the difference between a stuck pixel and a dead pixel?
A dead pixel stays dark, so it is most visible on a white or bright solid colour. A stuck pixel keeps one sub-pixel lit and is most obvious on a pure black screen. Both are panel defects, and factory grading normally allows several dead pixels but zero bright ones.
How should I run the test?
Go full screen, dim the room, clean the screen first — dust is easily mistaken for a dead pixel — and set brightness to your normal working level. Spend ten seconds per colour and scan the whole panel, paying attention to corners and edges.
Why is the black screen not perfectly black?
An LCD backlight cannot switch off completely, so pure black still glows slightly; brighter corners or edges are ordinary backlight bleed. OLED panels can reach true black but may show faint blotches in low grey levels. Neither is a dead pixel.
Does the tool collect anything about my screen?
No. Colour switching, the full-screen request and the contrast maths all happen in your browser, the page makes no network requests, and no display information is read or stored.
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