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Dead Pixel & Screen Test

Pick a colour and press Start: your screen fills with it. Tap or use the arrow keys to step through white, black, red, green, blue and more, and look closely for dots that do not match.

Dead Pixel Test
Start from a colour or pattern
Change every

Runs in your browser. Colours change no faster than once per second.

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  • No signup
  • Nothing uploaded

How to use the Dead Pixel Test

  1. Clean the screen and turn the brightness up.
  2. Press Start full-screen test, or pick a colour to start from.
  3. Tap the screen or press the right arrow to see the next colour.
  4. Look closely at each colour for dots that don't match, then press Esc to finish.
  5. If you find one, photograph it up close and contact the seller or manufacturer while you are still inside the return window.

What this screen test checks

Each colour lights only some sub-pixels, so problems that hide on one colour show up on another:

  • White shows dead pixels and colour tint
  • Black shows stuck pixels and backlight bleed
  • Red, green and blue check each sub-pixel colour on its own
  • Grey gradient and grid reveal banding, uneven brightness and distorted lines
  • Checkerboard shows uneven pixels and blur along sharp edges
  • Colour bars and red, green and blue ramps show colour accuracy and banding in each channel

Dead pixels and your warranty

The ISO 9241-307 standard sorts pixel faults into three kinds: a bright pixel that stays lit, a dark pixel that stays off, and a sub-pixel fault where one red, green or blue part is stuck. It then sets fault classes that say how many of each are allowed per million pixels. Class 0 allows none; higher classes allow more.

Many manufacturers sell their screens under Class II. For example, Dynabook’s pixel policy allows up to 5 bright pixels, 5 dark pixels and 8 sub-pixel faults on a Full HD (1920 × 1080) screen before it counts as faulty. Policies differ between makers and models.

  1. Test straight away. Run this test the day the screen arrives, while the store’s return window is open. A return is usually easier than a warranty claim.
  2. Record it. Photograph the fault up close on the colour where it shows best, plus a wider shot of the whole screen.
  3. Check the policy. Search for your model’s “pixel policy” on the manufacturer’s site and count the faults against it.
  4. Contact the seller or maker with the photos, the model and where on the screen the fault is.

Why there’s no stuck pixel fixer here

Stuck pixel fixers flash rapidly changing colours over the stuck spot, often many times a second. Flashing faster than three times a second can trigger seizures in people with photosensitive epilepsy, and the fixers often don’t work. This test never changes colours faster than once a second.

Safer things to try:

  • Leave the screen on a solid colour or the normal desktop for a few hours; some stuck pixels recover with use.
  • Turn the screen off and unplug it for a few hours, then test again.
  • If the pixel stays stuck, use the return window or warranty.

When to use it

  • Before buying a second-hand laptop, phone, tablet or monitor
  • When a new screen arrives, while you can still return it
  • After a drop or a repair

Frequently asked questions

What is the difference between a dead and a stuck pixel?

A dead pixel stays black on every colour because it gets no power. A stuck pixel stays one colour, usually red, green or blue, and is easiest to see on a black or white screen.

How do I check for backlight bleed?

Use the black screen in a dark room. Light leaking from the edges or corners is backlight bleed. A little is normal on LCD screens; bright patches are not.

What should I check when buying a used laptop or monitor?

Run every colour, then the grey gradient and grid. Look for dead or stuck pixels, uneven brightness, colour tint on white, and lines or bands in the gradient.

Can this test fix a stuck pixel?

No. Pixel fixers flash colours many times a second, which can trigger seizures in people with photosensitive epilepsy, and there is little evidence they work. Instead, leave a solid colour on for a while, power the screen off for a few hours, and use the warranty if the pixel stays stuck.

Is it a dead pixel or a speck of dust?

Dust sits on top of the glass, so it looks the same on every colour and moves or wipes away. A dead or stuck pixel is inside the panel, lines up exactly with the pixel grid and changes how it looks as the colours change.

How many dead pixels are allowed under warranty?

It depends on the maker. Many follow the ISO 9241-307 standard, which sets pixel fault classes. Under Class II, which many manufacturers use, a Full HD screen can have a few bright, dark and sub-pixel faults before it counts as faulty. Check your model's pixel policy and test while you can still return it.

Does pressing on a stuck pixel fix it?

Sometimes gentle pressure through a soft cloth frees a stuck pixel, but pressing can also damage the panel or add more faults, and it may void the warranty. Try the warranty first.

Can I test a phone, tablet or TV?

Yes. Open this page on the device and press Start; it fills the screen in any modern browser. On a TV, use the built-in browser or cast a browser tab. On OLED screens, a faint image of something that was on screen for a long time is burn-in, not a stuck pixel.

Last updated: · Sources: Dynabook: Pixel policy (ISO 9241-307 Class II), W3C: Understanding WCAG 2.2, Three Flashes or Below Threshold

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