Free Open Source Dead Pixel Test Online

What Is a Dead Pixel Test?

A dead pixel test is a full-screen monitor check that helps you find pixels that stay permanently black while the rest of the display changes color. This kind of defect is easiest to confirm when you display solid white, red, green, or blue backgrounds and scan the panel carefully from corner to corner.

Our browser-based screen tester is useful for new monitors, laptop displays, portable screens, tablets, and phones. If you are not sure whether the defect is a dead pixel or a colored stuck pixel, compare this page with our dedicated stuck pixel test.

How LCD and OLED Pixels Work — Why Pixels Die

An LCD monitor builds its image from millions of sub-pixels arranged in a grid. Each full pixel contains one red, one green, and one blue sub-pixel. A backlight shines through a liquid crystal layer. When voltage is applied to a sub-pixel, the crystals align and allow light to pass through a color filter. A dead pixel is one where the transistor or liquid crystal cell controlling that pixel has permanently failed — no voltage means no crystal alignment, no light passes through, and the pixel stays black on every color background.

OLED displays work differently: each sub-pixel is a self-emitting organic compound that produces its own light when current flows through it. A dead OLED sub-pixel occurs when the organic material burns out or the driving circuitry fails. Because OLED pixels produce their own light, a truly dead OLED pixel also appears black on any background.

Common causes of dead pixels include:

• Manufacturing defect: The most common cause. A tiny dust particle during panel construction or a micro-crack in the TFT layer can permanently disable a pixel before the monitor ever ships.
• Physical impact: A hard press or drop can crack the LCD layer, killing individual pixels or entire clusters near the impact point.
• Electrical surge: Voltage spikes through the display cable or power supply can burn out the thin-film transistors that control individual pixels.
• Long-term OLED degradation: OLED organic compounds degrade over time. Pixels that have displayed high-brightness content for thousands of hours may develop reduced output and eventually fail entirely.

How to Spot a Dead Pixel Quickly

1. Clean the display surface gently with a microfiber cloth so dust specks are not mistaken for pixel defects.
2. Open the screen test in full-screen mode (press F11 in most browsers).
3. Switch through white, then red, then green, then blue solid screens.
4. Inspect the center first, then scan slowly toward the edges and corners.
5. Repeat on the black screen to confirm any bright spots are stuck pixels rather than dead ones.
6. Retest under different lighting conditions — a dark room makes small defects easier to see.

Dead Pixel vs Stuck Pixel — Key Differences

A dead pixel appears black because its transistor or organic compound no longer responds to any signal. It stays dark on every color background including pure white, making it visible primarily against bright backgrounds.

A stuck pixel usually remains one fixed color — commonly red, green, blue, or white — because one or more sub-pixels are permanently switched on. It stands out most clearly against contrasting backgrounds. On the white screen, a stuck red pixel looks like a red dot. On a red screen it may be invisible.

That distinction matters practically: a stuck pixel may sometimes respond to pixel-massage techniques (rapidly cycling colors at the stuck pixel location can occasionally unstick the crystal), while a dead pixel with a failed transistor almost never recovers. If the defect looks colored rather than black, switch to the stuck pixel test page for targeted checks.

Common Problems and Solutions

• One tiny black dot visible only on bright backgrounds: This is a classic dead pixel. If it appears on white, red, green, and blue screens but disappears on black, it is almost certainly a dead pixel rather than a scratch or dust particle. Confirm by running through all color screens twice.
• Cluster of dark dots near a corner: Impact damage or a manufacturing pressure defect. Pixel clusters near the corners or edges are particularly common on panels that were stored or transported under pressure. There is no software fix; evaluate whether the cluster qualifies for the manufacturer's warranty policy (most require a minimum pixel count).
• Defect visible on some color screens but not others: This suggests a stuck sub-pixel rather than a fully dead pixel. Use the stuck pixel test to cycle through more targeted colors and check each sub-pixel channel independently.
• Defect appeared after a firmware update: Display firmware rarely affects individual pixels. If a dot appeared after a driver or firmware change, compare the result in multiple browsers and on a different OS to rule out a rendering artifact before concluding the panel itself is damaged.