Dead pixel test
Fill the whole screen with one flat colour at a time and look for a dot that does not change with it.
Red, green, blue, white and black — enough to find a dead pixel or a stuck subpixel.
Manual waits for a click, an arrow key or the space bar. A timer is easier when you want both hands free to look at a corner of the panel.
Screens in this run
A black dot here means the red subpixel never lights up.
A black dot here means the green subpixel never lights up.
A black dot here means the blue subpixel never lights up.
All three subpixels at full. A coloured or dark dot is a fault; a fuzzy grey speck is usually dust.
All subpixels off. Any bright dot is a stuck pixel, not a dead one.
What did you see?
Your display
Finding the pixel
- Clean the panel first. A dust speck on a black screen is indistinguishable from a stuck white subpixel until you wipe it.
- Sit close enough that a single pixel is resolvable — roughly an arm’s length on a 27-inch 1440p panel, closer on a 4K one.
- Scan in bands. Sweep left to right across the top third, then the middle, then the bottom, instead of staring at the whole screen at once.
- Black and white do most of the work: black finds stuck pixels, white finds dead ones. The primaries then tell you which subpixel is at fault.
- Photograph the fault on both the black and the white screen with exposure locked. Retailers usually ask for evidence on both.
- Turn off night light, HDR and any vendor picture enhancement first — they change what reaches the panel, and a filtered white is not a full-intensity white.
- On a laptop, press gently around a suspected cluster: if the dots move or spread, that is pressure damage in the panel rather than individual pixel failure.
A dead pixel only becomes visible against a field of one flat colour, which is the whole reason this test exists: on a normal desktop a single failed pixel disappears into the picture. The page paints the entire panel one colour at a time — red, green, blue, white and black in the standard run, plus cyan, magenta, yellow and 50 percent grey in the extended one — and you look for the dot that does not change with the rest of the screen. Each screen carries a one-line caption saying what that particular colour reveals, because the colour a fault shows up on is what tells you whether a subpixel is dead, stuck, or nothing more than dust. When you have found something, a three-way identification block turns what you saw into a verdict and a next step.
Key facts about Dead pixel test
| Standard run | red, green, blue, white, black — five flat sRGB fields |
|---|---|
| Extended run | adds cyan, magenta, yellow and 50% grey, nine screens in total |
| Why the secondaries | cyan isolates a red subpixel stuck on, magenta a green one, yellow a blue one |
| Advancing | click or tap, or press the right arrow, Space or Enter; left arrow steps back |
| Auto-advance | off, or every 3, 5 or 10 seconds so both hands are free |
| Exit | Escape, the exit button, or leaving fullscreen by any other route |
| Fullscreen | document.documentElement.requestFullscreen(); a refusal is reported on screen, not hidden |
| Cursor | hidden after three seconds of stillness — a still cursor looks like a bright pixel |
| Coverage | each screen is ticked off once it has been shown, so none is skipped |
| Identification block | three observations map to dead pixel, stuck subpixel, or dust on the panel |
| Display facts shown | screen.width, screen.height, devicePixelRatio, colour depth |
| What it cannot do | find the pixel for you — there is no camera and no screen capture; your eyes are the detector |
What happens to your file
There is nothing to upload, because there is no file. Each screen is a single fixed-position div with a CSS background colour, drawn in this tab, and the fullscreen request goes to your own browser through the Fullscreen API. No image of your screen is captured, no measurement is transmitted, and this page writes nothing at all to cookies, localStorage or sessionStorage — close the tab and the coverage ticks are gone. The display facts shown at the bottom (resolution, pixel ratio, colour depth) come from window.screen, which every page can already read and which is not sent anywhere either.
About this tool
- 1
Clean the screen first
Switch the monitor off, look at it under a bright light at an angle and wipe it with a dry microfibre cloth. A dust speck on a black field is indistinguishable from a stuck white subpixel, and this step removes most false alarms before you start.
- 2
Pick the run length
Standard is five screens and finds dead and stuck pixels. Extended adds cyan, magenta, yellow and mid grey, which pin down which single subpixel is at fault and reveal low-level unevenness that a full-white screen hides.
- 3
Choose manual or timed
Manual waits for a click, an arrow key or the space bar. A 3, 5 or 10 second timer is better when you want both hands free to lean in on a corner of the panel.
- 4
Go fullscreen and scan in bands
Press the start button, then sweep your eyes left to right across the top third of the screen, then the middle, then the bottom. Scanning in bands finds a single pixel; staring at the whole screen does not.
- 5
Watch black and white most closely
Black finds pixels stuck on — any bright dot is a fault. White finds pixels that are dead — any dark or coloured dot is a fault. The primaries then tell you which of the three subpixels is responsible.
- 6
Note where the fault sits
Faults in the centre third of the panel are treated differently from faults near the edge by most manufacturers' pixel policies, so record the position as well as the count.
- 7
Use the identification block
Pick the line that matches what you saw. Black on every colour means a dead pixel that will not recover; a coloured dot on black means a stuck subpixel worth trying to revive; a speck only on white is almost always dust.
| Browser support | any browser with the Fullscreen API — Chrome, Edge, Firefox, Safari and Opera on desktop |
|---|---|
| iOS Safari | has no fullscreen for page elements; the colours still fill the page but browser chrome covers the panel edges, which the page tells you when it happens |
| Colour values | exact sRGB hex — #FF0000, #00FF00, #0000FF, #FFFFFF, #000000, #00FFFF, #FF00FF, #FFFF00, #808080 |
| Colour pipeline | your OS colour profile, night light, HDR mode and any vendor picture mode all sit between this page and the panel |
| OLED and QD-OLED | black is a true off state, so a stuck pixel stands out far more than on an LCD |
| Multi-monitor | fullscreen fills the screen holding the browser window — drag the window across to test the second display |
| Phones and tablets | tap to advance works, but edge faults cannot be judged without fullscreen |
| Account or install | none — no signup, no extension, no download |
- Sit close enough that one pixel is resolvable — roughly arm's length on a 27-inch 1440p panel, and closer on a 4K one.
- Turn off night light, blue-light filters, HDR and any vendor picture enhancement before you judge anything; a filtered white is not a full-intensity white.
- Photograph a fault on both the black and the white screen with the camera's exposure locked. Retailers usually want evidence on both.
- Check the manufacturer's pixel policy before starting a return: most state a number of faulty pixels, and several treat the centre of the panel more strictly than the corners.
- On a laptop, press very gently around a suspected cluster. If the dots move or spread, that is pressure damage to the panel rather than individual pixel failure.
- Run this test again after ten to twenty minutes of the stuck-pixel fixer in the monitor test suite — that is the only fault here that can actually be repaired.
- A whole line of dead pixels across the screen is a driver or connector fault, not a pixel problem; reseat the cable before assuming the panel is finished.
- Fullscreen colour cycle in five or nine flat sRGB fields
- Per-screen caption explaining what that colour reveals
- Manual advance or a 3, 5 or 10 second timer
- Keyboard control with arrows, Space, Enter and Escape
- Dead versus stuck versus dust identification block
- Coverage ticks so no screen is skipped
- Fullscreen refusal reported instead of silently ignored
- Inspecting a brand-new monitor or laptop while the return window is still open.
- Checking a second-hand screen before handing over money for it.
- Confirming whether a dot you noticed in a dark game scene is a stuck pixel or a smudge.
- Gathering photographic evidence of a pixel fault for a warranty claim.
- Re-testing after a stuck-pixel fixer run to see whether the subpixel has come back.
- Comparing two panels in a shop or at home on exactly the same set of colours.
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