Dead pixel test: full screen monitor test

A full screen monitor test for faulty pixels

This dead pixel test fills your whole screen with one solid color, then the next: black, white, red, green, blue, cyan, magenta, yellow and 50% gray. On a plain background, a dot that does not follow the color stands out at once. It works as a screen test for a monitor, laptop, tablet or phone, with nothing to download and nothing sent anywhere.

Before you start, the tool shows your screen resolution, device pixel ratio, window size and color depth. A 4K monitor at 3840 × 2160 set to 150% scaling, for example, reads "2,560 × 1,440" as screen resolution, a ratio of 1.5 and "3,840 × 2,160" in physical pixels: 8,294,400 pixels to check.

Dead, stuck or hot pixel?

• Dead pixel: stays black whatever color is shown. Easiest to spot on white.
• Stuck pixel: stays lit in one color, often red, green or blue. Easiest to spot on black.
• Hot pixel: stays white or very bright all the time, clearly visible on black.

These terms describe what you see; only a repair technician can tell the exact cause.

How to run the screen test

1. Turn the screen off and wipe it with a soft, dry cloth.
2. Dim the room lights: defects are easier to see in the dark.
3. Click "Start the test" or press the space bar. The page goes full screen.
4. Move to the next screen with a click, a tap, the space bar or the right arrow key. The left arrow goes back, Esc ends the test.
5. On each color, scan the screen up close, strip by strip. The color name shows for 1.5 seconds; the cursor hides after 2 seconds.

Under "Extra screens" you can add "Grayscale bands" (16 steps), "1-pixel checkerboard" (alternating black and white pixels, which reveals scaling blur), "Sharpness test pattern" and "Slow color scroll": the background drifts slowly and a stuck pixel stays still.

Fixing a stuck pixel: what you can try

A stuck pixel sometimes starts working again when its color changes quickly for a while. There is no guarantee, and it rarely helps a dead pixel. The "Fix a stuck pixel" section shows a small square that cycles through red, green, blue, black and white. Drag it over the pixel, or move it with the arrow keys.

Flashing only starts once you tick "I understand the warning". "Color changes" can be set from 1 to 3 per second, never faster, and "Duration" to 1, 2, 5 or at most 10 minutes. At 3 changes per second for 10 minutes, that is 1,800 changes. Run the test again afterwards. Do not press hard on the screen: you can damage the panel.

Epilepsy warning. Rapid flashing is not recommended for people with photosensitive epilepsy. If in doubt, do not start it. If your device asks for reduced motion, flashing stays turned off.

Warranty, returns and used screens

Many manufacturers apply a tolerance policy based on the number and type of faulty pixels, often modeled on the pixel classes of the ISO 9241-307 standard, so check the warranty terms for your model. If you buy online in the European Union, you generally have 14 days to withdraw from the purchase, with some legal exceptions; in other countries, check the seller's return policy. Either way, run the test as soon as the screen arrives.

Buying a used monitor or laptop? Open this page on it and go through all 9 colors.

Frequently asked questions

Can a dead pixel come back on its own?

It is rare. A stuck pixel sometimes recovers after a few days or after flashing. Under warranty, contact the seller.

Why do I see a dot on black but nothing on white?

That points to a stuck or hot pixel: it is always lit, so it blends into white and stands out on black. A dead pixel shows up on white.

Does the test work on a phone?

Yes. Tap the screen to move to the next color. If the browser blocks full screen, the test fills the whole window instead.

Can this test damage my screen?

No. It shows colors like any other image.