When to use it
Use this tool to check a monitor, laptop, TV or phone screen for faults. It is especially useful when you buy a new or second-hand device, before the return period ends, or when you notice a mark on the screen and want to know if it is a pixel fault, backlight bleed or just dust.
How to use it
Choose a test and press Start test. Tap or press → to move to the next screen, ← to go back and Esc to exit.
- Dead and stuck pixels: solid colors fill the screen. Look for dots that stay black, white or one color.
- Color banding: smooth gradients. Visible stripes or steps mean limited color depth.
- Backlight and uniformity: dark and mid-gray screens reveal light bleeding from the edges, cloudy patches and uneven brightness.
- Sharpness and scaling: fine one-pixel patterns. Blur or shimmering patterns mean the picture is being scaled.
Your display shows the screen size the browser reports and an estimate of the physical resolution. The Stuck pixel exerciser flashes colors in a small square that you drag over a stuck pixel.
Worked example
You have just bought a laptop. In a dim room, run Dead and stuck pixels and slowly look over each color. On the black screen everything is dark, but on the white screen you spot one tiny black dot near the top right. It is black on every color, so it is a dead pixel. Take a photo and contact the seller.
Next, run Backlight and uniformity. A faint glow at the bottom corners on the black screen is backlight bleed, which is normal in small amounts on many LCD screens.
OLED and LCD screens
Phones and many TVs use OLED, where each pixel makes its own light, so backlight bleed does not happen, but burn-in can. Look for faint ghost images, such as old status bars, on the gray screens. LCD screens are more likely to show bleed and clouding.
Tips
- Clean the screen first. Dust can look like a dead pixel.
- Test in a darker room. Backlight problems are much easier to see.
- Look from straight ahead. Viewing from an angle can make normal screens look uneven.
- Turn off night light or blue light filters. They change the colors shown.
Common mistakes
- Rushing the color screens. Take your time and check each area.
- Pressing on the screen to fix a pixel. It can cause more damage.
- Testing at the wrong scaling. For the sharpness test, set your display to its native resolution and 100% scaling if possible.