Quick answer
A dot that stays black on every color is a dead pixel. A dot stuck on one color is a stuck pixel, which can sometimes be fixed. Show each full-screen color and look closely.
How to use the Dead Pixel Test
- Clean your screen with a soft cloth so dust isn't mistaken for a pixel fault.
- Click Start full-screen test. The screen fills with one color.
- Look closely across the whole screen. Click or press the right arrow key to move to the next color.
- A dot that stays black on every color is a dead pixel. A dot that stays red, green, blue or white is a stuck pixel.
- Press Esc to exit. If you found a stuck pixel, try the stuck pixel fixer.
Example
On a new laptop you notice a tiny bright green dot in the black test screen, and it stays green on the blue and red screens too. That's a stuck green subpixel. You run the stuck pixel fixer over it for 20 minutes; if it doesn't go away, you check the manufacturer's pixel policy and contact the seller while you're still within the return period.
How it works
Every pixel on an LCD or OLED screen is made of three subpixels: red, green and blue. By filling the screen with pure colors, each subpixel is tested on its own:
- Black screen reveals stuck pixels (bright dots) and backlight bleed at the edges.
- White screen reveals dead pixels (dark dots) and dust under the panel.
- Red, green and blue reveal individual subpixels that are stuck on or off.
The stuck pixel fixer rapidly cycles colors in a small square that you drag over the faulty pixel. The fast changes can sometimes “unstick” a pixel that's stuck in one state. It doesn't work on truly dead pixels, which have no power or are physically damaged.
Check a new screen properly
- Test on day one: most shops accept returns for pixel faults only within their normal return window, often 14-30 days.
- Use a dark room for black, bright light for white: stuck pixels stand out on black in the dark, and dark specks show up on white in normal light.
- Dust or pixel? Dust on the surface casts a slight shadow and moves when you wipe the screen gently. A pixel fault is perfectly sharp and doesn't move.
- Fixer didn't help after 30 minutes: try once more the next day. If the pixel still doesn't change, it's very unlikely to recover.
- Take a photo for warranty claims: photograph the pixel on the color where it's most visible, with part of the screen edge in the frame.
Frequently asked questions
What's the difference between a dead and a stuck pixel?
A dead pixel gets no power and stays black on every color. A stuck pixel has one or more subpixels permanently on, so it shows as a red, green, blue or white dot. Stuck pixels can sometimes be fixed; dead pixels usually can't.
Will the stuck pixel fixer damage my screen?
No. It only displays changing colors, which the screen is designed to do. Run it for 10-30 minutes. If the pixel doesn't recover, it's unlikely to.
How many dead pixels are acceptable?
It depends on the manufacturer. Many brands follow the ISO 9241-307 pixel classes, which allow a small number of faulty pixels, while some offer zero-dead-pixel guarantees. Check your manufacturer's pixel policy.
Can I test a TV or phone with this?
Yes. Open the page on a phone or a smart TV browser, or connect a laptop to the TV and run the test full screen.
What is backlight bleed?
Uneven light leaking from the edges of an LCD screen, most visible on the black test screen in a dark room. Some bleed is normal on LCD panels; OLED screens don't have it.