How the dead pixel test works
The test turns your whole screen into one solid colour: black, white, red, green, blue, then grey. Each colour drives the sub-pixels in a different way, so a faulty pixel that hides on one colour stands out on another.
- Wipe the screen with a dry microfibre cloth. Dust and smudges are the most common false alarm.
- Dim the room and sit at your normal distance. Then lean in for a second pass.
- Start the test. Click, press Space or use the arrow keys to change colour. On a phone or tablet, tap the screen.
- Scan in strips, left to right and top to bottom, rather than staring at the centre.
- Press Esc to leave, then tell the tool what you saw to get a verdict.
The page asks your browser for full screen with the Fullscreen API and keeps the screen awake with the Wake Lock API, so the display does not dim in the middle of the test. Nothing is recorded: everything runs on your device.
Dead, stuck or hot: read what you see
| What you see | Type | Fixable? |
|---|---|---|
| A black dot on white, red, green and blue | Dead pixel | No, the transistor no longer powers it |
| A red, green or blue dot on black or grey | Stuck pixel (one sub-pixel on) | Sometimes |
| A cyan, magenta or yellow dot | Stuck pixel (two sub-pixels on) | Sometimes |
| A white dot, clearest on black | Hot pixel (all sub-pixels on) | Rarely |
| A dark or bright spot that moves when you wipe | Dust or a smudge | Clean the screen |
| A cloudy light patch near the edges on black | Backlight bleed, not a pixel | No, it is a panel trait |
A useful trick: point your phone camera at the spot and zoom in. A real pixel defect is a sharp square aligned with the pixel grid. Dust is soft and casts a shadow.
What to do with a faulty pixel
Stuck pixel. Give it a few days of normal use: some recover on their own. A stuck pixel fixer flashes rapid colours over the spot for 10 to 20 minutes, which can unstick the sub-pixel. A stuck pixel fixer is coming to FragTools soon. Gentle pressure with a soft cloth while the screen is on also works for some people, but press lightly: too much force can create more dead pixels.
Dead or hot pixel. Software will not revive it. If the monitor is new, use the return window of the shop first, it is usually simpler than the warranty. Then read the maker’s pixel policy: many follow ISO 9241-307 class II, which accepts a small number of faulty pixels per million, while some premium lines promise zero bright pixels.
Note the position and the colour where the defect shows, and take a photo. It makes a claim much easier.
Limits of a browser test
The test shows exact solid colours, but your system can still change them on the way to the panel: night light, HDR tone mapping or a colour profile can tint white and grey. Turn them off for the test. On a phone, the browser bars may stay visible when full screen is not supported, so scroll them away and check the edges by eye.
A pixel that flickers only in games, or a line of pixels, points to a cable, driver or panel connector problem rather than a single dead pixel. Try another cable and port, and test again.
Frequently asked questions
How do I check my monitor for dead pixels?
Wipe the screen, dim the room, start the test and go through every colour. On each one, scan the whole screen slowly, corner to corner. A dead pixel shows as a dark dot on white, red, green and blue. A stuck pixel shows as a coloured dot that does not change.
What is the difference between a dead, stuck and hot pixel?
A dead pixel stays dark whatever the colour, because it gets no power. A stuck pixel has one or two sub-pixels stuck on, so it shows red, green, blue, cyan, magenta or yellow on most backgrounds. A hot pixel is stuck fully on and shows white, most visible on black.
Can a dead pixel fix itself?
A truly dead pixel almost never comes back. A stuck pixel sometimes does, on its own after a few days or with a tool that flashes colours quickly over it for 10 to 20 minutes. It is worth trying before a return, never instead of checking the return window.
How many dead pixels are acceptable?
It depends on the brand. Many monitors follow ISO 9241-307 class II, which tolerates a few faulty pixels per million. Some makers promise zero bright pixels on premium lines. Check the pixel policy of your brand and the shop's return window, which is often shorter and simpler.
Does this work on a phone, a TV or an OLED screen?
Yes. On phones the test fills the browser window when full screen is not available. On a smart TV, open the page in the TV browser or cast a laptop at native resolution. OLED panels can have dead pixels too, but burn-in is a different problem that this test will also reveal on grey.
Updated October 26, 2026