Monitor Test — Check for Dead & Stuck Pixels

How to find dead pixels and stuck pixels

• Black screen: look for a point that stays lit in the dark (a white, red, green or blue dot). That is a stuck pixel (stuck lit).
• White screen: look for a black or dark point on the all-white field. That is a dead pixel (stuck off).
• Red / green / blue screen: look for a point that does not light up in that color, or shows a different color. That is a missing or stuck subpixel.
• Gray / gradient: check for uneven brightness, color tint or banding (these depend on viewing distance and lighting, so treat them as rough guides).

If you see a point, first wipe the screen gently with a soft cloth — dust or a smudge will wipe away. A point that stays after cleaning may be a dead or stuck pixel.

How to use it — checking a monitor for dead pixels

1. Press "Start full-screen test". On supported browsers the display switches to full-screen.
2. A black screen appears first. Look closely for any point that stays lit in the dark.
3. Click/tap, or use the arrow keys or space, to move through white → red → green → blue → gray. On each color, look for points that do not match or uneven areas.
4. After the solid colors come a gradient, a checkerboard and a solid gray, which give a rough read on banding, bleed and unevenness.
5. When you are done, press Esc or the × in the top corner to exit. Moving past the last pattern also ends the test automatically.

What makes this tool useful

• Shows black, white, red, green, blue and gray full-screen in order so you can eyeball dead pixels (stuck off) and stuck pixels (stuck lit).
• Extra patterns: a gradient (rough guide to banding), a 1-pixel checkerboard (rough guide to bleed / sharpness) and a solid gray (rough guide to unevenness).
• No camera, mic or files — it only paints colors on the screen. Nothing is sent to a server.
• Works for phone and tablet screens too, not just computers (display is limited where true full-screen is unsupported).

Which screen shows what

Different colors make different kinds of pixel faults easier to spot.

• Black screen: the easiest way to find a stuck pixel (stuck lit). In a dark room, even a faintly glowing point stands out.
• White screen: makes dead pixels (stuck off) and faint smudges or uneven areas easier to see.
• Red / green / blue screen: checks each subpixel (the tiny red, green and blue dots that make up a pixel). A point missing one color can show up here.
• Gradient / checkerboard / gray: less about dead pixels and more a rough guide to overall uniformity, bleed and color unevenness (how they look varies with viewing distance and ambient light).

Things to keep in mind

• Whether a dead pixel can be exchanged or returned depends on the store's or maker's policy. The threshold differs by product, so check right after buying and ask the seller or maker for their exact terms.
• International standards for allowable pixel defects exist (such as ISO 9241-307), but which one a maker uses is up to them. There is no universal "this many = defective" rule.
• A point on the screen may just be dust or a smudge. Wipe gently with a soft cloth to tell them apart.
• OLED panels are prone to burn-in (image retention) when the same still image stays on for a long time. Finish the test promptly once you are done.

When it will not go full screen (e.g. on iPhone)

Some environments, such as Safari on iPhone, do not support the browser Fullscreen API. The colors still display, but browser UI (the address bar and so on) stays on part of the screen, so the check is a rough guide only. For a larger view, try adding the page to your home screen and opening it from there, or use an up-to-date Chrome, Edge or Firefox on a computer.