slopbin.org / dead-pixel-test
Dead Pixel Test
Check a monitor, laptop screen, tablet or phone for dead and stuck pixels. Full-screen solid colours, a grid overlay that exposes defects, and a text sharpness check.
1. Pick a colour
Solid colours are the only way to spot a defect. Choose one, then start the full-screen test.
White
Black
Red
Green
Blue
Cyan
Magenta
Yellow
50% grey
25% grey
Defects marked0click a defect in the test
Current colourWhite#ffffff
Screen size—viewport
Pixel ratio—device pixels per CSS pixel
2. Text sharpness check
Look for jaggies, colour fringing or uneven spacing. Hold your nose to the screen at normal viewing distance.
10px — the smallest text most UIs still use
12px — body text on many websites
14px — the browser default
18px — large interface text
24px — heading size
Il1 O0 rn m 5S 8B 2Z — confusable characters at 10px
How to test for dead pixels
- Pick a solid colour, white or black first.
- Click Start full-screen test.
- Inspect the screen, then press the right arrow for the next colour.
- Turn on the grid overlay and any always-on text to expose defects hiding on flat colour.
- Click a defect to pin a marker and record its position.
- Press Esc to leave and review your list.
Colour cycling inside the test
| Key | Action |
|---|---|
| Right arrow / Space | Next colour |
| Left arrow | Previous colour |
| G | Toggle the grid overlay |
| T | Toggle always-on text |
| M | Toggle the marker cursor |
| Esc | Exit the full-screen test |
What each defect type looks like
- Dead pixel — always black on every colour. Caused by a failed transistor.
- Stuck-on pixel — always one colour, most often red, green or blue. Very visible on black.
- Stuck-off pixel — always black, visible only on light colours.
- Cluster — several defects together, usually a damaged panel section rather than isolated pixels.
- Burn-in — a faint ghost of an icon or toolbar that shows on both light and dark colours.
Dead pixel test limitations
- The browser paints the colour; it cannot inspect the panel, so this is a visual check and results depend on your eyes.
- Screen smoothing, eye strain and bright room lighting all hide defects. Dim the room and get close for the low-contrast greys.
- An OLED screen may hide a defect on one colour and show it clearly on another, so test all ten colours.
- Defects often move with screen pressure. Press gently near a suspect pixel to confirm before logging it.
If you find a defect
Photograph each defect on the colour where it shows worst, count them, then check the manufacturer's dead pixel policy. Most allow two or three on a large panel and none in the centre third.
FAQ
What is a dead pixel?
A dead pixel is a subpixel that never lights up, so it stays black on every colour. A stuck pixel always shows the same colour and is usually more common than a fully dead one.
How do I find dead pixels on my screen?
Start the full-screen test, then step through white, black, red, green and blue one colour at a time. Stuck or dead pixels stand out clearly against a flat solid colour.
Does this dead pixel test work on a phone?
Yes. It runs on any device with a browser, including phones and tablets. Rotating the device is a common trick because subpixel layout changes with orientation on some screens.
How many dead pixels should a new monitor have?
Most manufacturers allow a small number of dead pixels under their warranty policy, often two to three on a large panel. Check the warranty terms for your specific model before returning it.
Why do I see defects only on certain colours?
A single stuck subpixel only shows its colour when that subpixel is asked to show it. On a solid black or blue screen it can be invisible, and the grid overlay reveals it on other colours.