Dead pixel test
One colour at a time, edge to edge, to find the pixel that isn’t right.
Look closely at each colour. A dot that stays black on white or on a colour is a dead pixel; a bright or coloured dot on black is a stuck pixel. Dust looks the same on every colour; wipe the screen first.
Nothing leaves your device
This tool runs entirely in your browser. What you type, play or record here stays on your device: nothing is uploaded or saved on a server.
Example
Checking a used 24-inch 1080p monitor before paying for it
Sam is buying a second-hand 24-inch monitor (1920 × 1080) and tests it at the seller’s table with a laptop. The panel has 2,073,600 pixels, each about 0.28 mm across (91.8 pixels per inch), so a dead one is a speck you only see from close up. Settings: Colours “Basic (5 colours)”, Change automatically “Off”.
- Set the laptop to extend its display to the monitor, drag the browser window onto it and wipe the screen. Start test fills that screen with black.
- On black, look for lit dots. Then click or press → for white, red, green and blue, and look for dark or wrongly coloured dots, edges and corners included.
- Keep the mouse still: after 2 seconds the cursor and the top bar hide, so the arrow isn’t mistaken for a pixel. ← goes back to compare; after blue the test ends.
| Colour | A dot on it means |
|---|---|
| Black | a lit dot (red, green, blue or white): a stuck pixel or subpixel |
| White | a black dot: a dead pixel; a cyan, magenta or yellow dot: one dead subpixel |
| Red | a black dot: the red subpixel there is off, or the whole pixel is dead |
| Green | the same check for the green subpixel |
| Blue | the same check for the blue subpixel |
One black dot showed in the same place on white, red, green and blue, and nothing on black: a dead pixel. It stayed put when wiped, so it wasn’t dust. Sam photographed it on white with a phone and agreed a lower price; the other 2,073,599 pixels passed.
How it works
- Wipe the screen, then press Start test: the page goes full screen in one colour.
- Look over the whole screen, edges included, then click, tap or press → for the next colour.
- A dot that stays dark on white is a dead pixel; a bright dot on black is a stuck one. Press Esc to finish.
Frequently asked questions
- What is the difference between a dead and a stuck pixel?
- A dead pixel is always off: it shows as a black dot on every bright colour. A stuck pixel is always on in one colour — a red, green, blue or white dot that stands out on black.
- Can a stuck pixel be fixed?
- Sometimes a stuck pixel frees itself after hours of use or gentle pressure through a soft cloth; a dead pixel usually cannot be fixed. We don’t offer a flashing “fixer”: rapidly flashing colours can trigger seizures in people with photosensitive epilepsy.
- How many dead pixels are acceptable?
- It depends on the maker’s pixel policy (often based on ISO 9241-307 classes). Check your warranty terms — test a new screen as soon as it arrives, while you can still return it.
- Does it work on phones and TVs?
- Yes, in any browser. On an iPhone, which has no full screen for web pages, the colours fill the window; hide the address bar to see the edges.
- Can I take a screenshot of a dead pixel?
- No. A screenshot saves the picture the computer sends, which is flawless; the fault is in the panel. Photograph the screen with a phone instead, close up and in focus, on the colour where the dot shows best: white for a dead pixel, black for a stuck one.
- Can I start from one particular colour?
- Yes. Click one of the colour squares above the Start button and the test opens full screen on that colour; → and ← move on from there. With the extended set, the 11 squares include the pixel checker and the gradient.
- Is anything uploaded?
- No. It runs in your browser; nothing is sent anywhere.