How to test for dead pixels
- Wipe the screen with a dry microfiber cloth, so dust doesn't look like a defect.
- Set the brightness to a normal level and close any window that's covering part of the screen.
- Click Full screen. A short hint shows the controls, then fades away along with the cursor.
- Click, tap or press Space or → for the next color. Press ← to go back and Esc to exit.
- On each color, scan the screen in sections from one corner to the other. Look closely: one pixel on a high-resolution screen is tiny.
- If you find a spot, note its position and which colors it shows up on. That tells you what kind of fault it is.
Dead, stuck and hot pixels
Each pixel on an LCD or OLED screen is made of three subpixels: red, green and blue. Every color you see is a mix of those three at different strengths. A faulty pixel is one where some or all of its subpixels no longer follow the signal.
- Dead pixel: all three subpixels stay off, so the pixel is black on every color. It's easiest to spot on white.
- Stuck pixel: one or two subpixels stay on, so the pixel shows a fixed color, such as red, green, blue, cyan, magenta or yellow. It's easiest to spot on black.
- Hot pixel: all three subpixels stay on, so the pixel is white on every color. It stands out on black.
- Dead subpixel: one subpixel stays off. The pixel looks slightly off on white and goes dark on the color of the missing subpixel.
What each test color shows
| Color | Subpixels on | A faulty pixel looks like |
|---|---|---|
| Black | None | Any lit dot: a stuck pixel (colored) or a hot pixel (white) |
| White | Red, green and blue | A black dot (dead pixel) or a colored dot (dead subpixel) |
| Red | Red | A dark dot means the red subpixel is dead; a green or blue tint means one is stuck on |
| Green | Green | A dark dot means the green subpixel is dead; a red or blue tint means one is stuck on |
| Blue | Blue | A dark dot means the blue subpixel is dead; a red or green tint means one is stuck on |
| Cyan, magenta, yellow | Two of the three | A second check that confirms which subpixel is affected |
How the test works
The test fills your whole screen with pure colors such as #FF0000 (red only) and #FFFFFF(all three at full strength). Pure colors turn each subpixel fully on or fully off, which makes a pixel that doesn't respond stand out against the rest. Full screen mode uses your browser's Fullscreen API. Where that isn't available, the color fills the browser window instead. Nothing is uploaded: everything runs on your device.
What to do if you find a faulty pixel
- New screen: check the store's return window and the manufacturer's pixel policy before anything else. Policies set how many faulty pixels qualify for a replacement, and they vary by brand and model.
- Stuck pixel: these sometimes recover on their own with normal use. Some people run a video or tool that flashes colors over the spot. Avoid flashing tools if you're sensitive to flashing light.
- Dead pixel: a pixel that stays black on every color usually has a hardware fault that software can't repair.
- Pressing on the screen: pressure can damage the panel and may not be covered by the warranty, so leave it as a last resort on an old screen.
Also check your screen for backlight bleed and IPS glow, use thewhite screen to look for uneven brightness, and run theFPS test to confirm the refresh rate.