Dead pixel test
Fill the screen with solid colours to find dead and stuck pixels, backlight bleed and uniformity problems. Runs in your browser.
Runs in your browser
Pick a colour to fill the screen with. Click or press the right arrow for the next one, and Escape to come back.
Click or press → for the next colour · Esc to exit
How to use it
Pick a colour, and it fills the screen. Click or press the right arrow for the next one, and Escape to come back.
Work through all nine. A fault only shows against a field it does not belong to — a subpixel stuck on red is invisible on a red screen and obvious on a green one — so cycling through the set is the whole method.
Clean the screen first. Dust and dried droplets look exactly like dead pixels, and are the explanation far more often. Check with the screen off, too: a mark that is visible on a black screen and on a switched-off one is on the glass.
Dead is not the same as stuck
The two words are used interchangeably and describe different faults with different prospects:
| Looks like | Cause | Fixable | |
|---|---|---|---|
| Dead pixel | black on every colour | the pixel gets no power | No |
| Stuck pixel | one fixed colour, brightest on its complement | a subpixel is held on | Sometimes |
| Hot pixel | white on every colour | all three subpixels held on | Sometimes |
A stuck pixel is a transistor holding a value. It is occasionally freed by rapidly cycling colours in that area for a few minutes, or by very gentle pressure through a cloth with the screen off. Both are folk remedies with mixed results and a real risk of making things worse; neither does anything for a dead pixel, which has no signal at all.
What the warranty actually covers
Almost no manufacturer will replace a panel for one dead pixel, and this is where people are caught out. The reference is ISO 9241-307 — now part of the ISO 9241-3xx series — which defines fault classes. Most consumer panels are sold as Class II, which permits, per million pixels:
| Fault type | Allowed |
|---|---|
| Type 1 — permanently lit pixel | 2 |
| Type 2 — permanently dark pixel | 2 |
| Type 3 — stuck subpixel | 5 |
A 1920×1080 screen is 2.07 million pixels, so a Class II panel can ship with roughly four dead pixels and ten stuck subpixels and still meet spec.
Check the seller’s own policy before the return window closes. Several manufacturers offer a zero-bright-pixel guarantee on professional monitors, and some retailers are more generous than the panel maker. The thresholds are commercial, not physical.
What else the colours show
The test is worth running on a screen with no dead pixels at all:
- Black in a dark room reveals backlight bleed — light leaking in from the edges of an LCD — and clouding, patchy brightness across the panel. Some is normal on an edge-lit LCD; a bright corner is not.
- White reveals uniformity problems and any yellow or pink tint across the panel.
- Grey is the most demanding: banding, dithering and colour casts that hide in extremes are visible in the middle.
- Red, green and blue each isolate one subpixel channel, which is what makes a stuck subpixel findable at all.
OLED screens are different
An OLED has no backlight, so there is no bleed to look for and black is genuinely black. What it has instead is burn-in: uneven ageing where a static element — a taskbar, a channel logo, a status bar — has been displayed for thousands of hours.
Solid colours find it. A mid-grey or a solid colour at moderate brightness shows a faint ghost of whatever was left on screen. The lower the brightness, the more visible it usually is.
What this page does not do
It fills the screen with a colour. There is no processing, no analysis and no camera — the judgement is yours, made with your own eyes. Nothing leaves the browser, because there is nothing to send.