Dead Pixel Test: Check Your Screen Online

How to test for dead pixels

1. Wipe the screen with a dry microfibre cloth, so dust isn’t mistaken for a faulty pixel.
2. Press Start full-screen test. Each pattern fills the whole screen.
3. Step through the colours with the arrow keys or Space, or click or tap the screen (the left third goes back). Press Esc to finish.
4. Scan the whole screen on every colour from your normal viewing distance, then look closely at anything suspicious. On a dense screen a magnifying glass or your phone camera’s zoom helps.

The controls fade after two seconds and the mouse pointer hides, so neither can be mistaken for a fault. Tick Auto-cycle to step through the patterns by themselves; they change no faster than once a second, well below the three flashes per second that accessibility guidelines treat as a seizure risk. The screen is kept awake during the test where the browser allows it.

Dead, stuck and hot pixels

Every pixel is made of red, green and blue sub-pixels, and each kind of fault shows up best on a different background:

On an LCD the result of a failed transistor depends on the panel. IPS and VA panels are normally black, so the pixel stays dark; TN panels are normally white, so it stays lit. On an OLED each sub-pixel makes its own light, and a dead one is simply dark.

Can a stuck pixel be fixed?

A stuck sub-pixel is still wired up but frozen in one state. Running a rapidly changing colour pattern over it for 10 to 30 minutes, often called pixel exercising, sometimes frees it; there is no guarantee, and fast flashing is unsuitable for anyone with photosensitive epilepsy. Pressing gently on the spot through a soft cloth is another old trick, but pressure can damage the panel, so treat it as a last resort. Dead and hot pixels usually come from a failed transistor or connection and cannot be repaired at home.

Backlight bleed and uniformity

Show Black in a dark room with brightness at your usual setting. Light leaking in from the edges that stays put when you move your head is backlight bleed. A silvery glow in the corners that changes with your viewing angle is IPS glow, which is normal for IPS panels. Grey 50% and Dark grey 5% reveal clouding, darker corners and tinted patches, and near-black banding on OLEDs. The gradients should look smooth: clear steps are banding, common on 6-bit panels and with some colour settings. On the checkerboard, white squares should be equally bright everywhere without glowing into their black neighbours. Phone cameras exaggerate bleed, so judge with your eyes.

Pixel fault policies

The ISO 13406-2 standard, since replaced by ISO 9241-307 but still quoted by many manufacturers, allowed a Class II panel up to 2 always-lit and 2 always-dark pixels plus 5 faulty sub-pixels per million pixels. A 1920 × 1080 screen has about 2.1 million pixels, so a few faults could still pass. Many brands publish stricter zero bright dot policies, and a retailer’s return window is often the simplest remedy, so test a new screen straight away.