Dead Pixel Test
Nine pure colors, full screen, with pixel-exact markers. 100% in your browser - nothing is uploaded.
1 min9 patterns
Click the preview to run it full screen
Your display
Updates when you move the window to another screen- Resolution
- ---
- device px
- Pixel ratio
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- devicePixelRatio
- Refresh rate
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- measured in this browser
- Color gamut
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- reported by the browser
- HDR
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- standard range
- Orientation
- ---
- current
How to run the dead pixel test
01Wipe the screen
Use a dry microfibre cloth. A speck of dust looks exactly like a dead pixel.
02Start it full screen
The pattern takes the whole panel, the controls hide on their own.
03Go through every color
Arrow keys or a swipe switch the nine colors. Scan each one corner to corner.
04Mark what you find
Press M (or Mark defects) and click the pixel. Drag the marker until it sits on it.
05Save the report
Copy it or save the PNG with the exact coordinates for the seller.
What to look for
- On white and the bright colors: a black dot that never changes. That is a dead pixel.
- On black: a red, green, blue or white dot. That is a stuck pixel, one or more subpixels locked on.
- On one primary only: a dot missing its color, a single dead subpixel.
- Along the edges and in the corners, where defects are easiest to miss.
What counts as a defect
- A dot that stays the same on every color and does not move with the image is a panel defect.
- A dot that wipes away or moves when you scroll is dust or a smudge, not a pixel.
- Many monitors are sold to ISO 9241-307 Class II, which tolerates a few faulty pixels per million. Check your brand’s pixel policy: some promise zero bright pixels.
What to do next
- Stuck pixel on black? Try the stuck pixel fixer for 10 to 20 minutes before you return anything.
- Dead pixel, or the fixer did not help: save the report with the coordinates and contact the seller inside the return window.
- Buying online in the EU you usually have 14 days to withdraw, so run this on the first day.
Other screen tests
Each one checks a different part of the panel. The guided check runs them all in order.
Uniformity & clouding
Flat greys and white show clouding, dirty-screen effect and tinted zones.
1 minGuide
Banding & gradients
256 equal steps per ramp. A good panel shows them evenly, a weak one clumps them.
1 minGuide
Sharpness & geometry
One-pixel grids, checkerboards and circles expose scaling blur and bad geometry.
1 minGuide
Refresh rate & tearing
Measures the real frame rate in this browser and shows tearing on a moving bar.
30 sGuide
About the dead pixel test
Fill the screen with pure black, white, red, green, blue and the secondary colors, one after another. A dead pixel stays dark on every color, a stuck one stays lit on black. Mark it: the marker records the exact device pixel, and you can drag it or nudge it 1 px at a time until it sits right on the spot.
It is one of the tests in the Screen & Monitor Test, which also runs a guided check through every test and ends in an inspection reportfor a return or RMA. Every pattern is drawn on your screen's own pixel grid, 100% in your browser - no upload, no install, no account needed.
Frequently Asked Questions
It depends on the manufacturer. Many monitors follow ISO 9241-307 Class II, which allows a small number of always-lit or always-dark pixels per million before the panel counts as faulty. Some brands offer a zero bright pixel guarantee. For a return inside the retailer’s window, one clearly visible dead pixel is usually enough.
Because that is the grid of the panel. With Windows scaling at 125% or a phone at 3×, one CSS pixel covers several panel pixels, so the test converts every click to the exact device pixel under it. Support staff can find the same spot from the numbers, whatever scaling their own screen uses.
Yes, and it is the most common false alarm. Dust sits on the surface and looks the same size on every color, like a dead pixel. Wipe the screen and look again: if the dot moves, smears or disappears, it was never a pixel.
Safari on iPhone does not allow web pages to go truly full screen. The test fills the whole visible area and hides all controls instead; rotate to landscape, or add the page to your Home Screen, to get the most of the panel in view. iPad and Android support real full screen.
No. Every pattern is drawn locally in your browser, and the inspection report is built and downloaded on your device. Nothing about your screen or your results leaves the browser, and no account is needed.
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