Dead Pixel Test

What this dead pixel test checks

A screen is made of millions of pixels, each built from a red, a green and a blue sub-pixel. A faulty one is easy to miss in normal use and hard to ignore once you have seen it. This test fills the screen with nine solid colours, one at a time, so that any pixel that does not follow the others stands out:

• Black reveals pixels that stay lit.
• White reveals pixels that stay dark.
• Red, green and blue check each sub-pixel on its own.
• Cyan, magenta and yellow light two sub-pixels at a time, which makes a single missing one visible.
• Grey shows both kinds of fault at once.

Unlike a simple colour slideshow, the test lets you mark what you find. You get a count by type, a comparison with the tolerance most manufacturers use, and a result you can keep or send to a seller. It works on monitors, laptops, televisions, tablets and phones, and nothing leaves your browser.

How to test your screen

1. Clean the screen with a soft dry cloth. Dust is the most common false alarm.
2. Raise the brightness and turn off night light, blue-light filters and any “eye comfort” mode, which tint the colours.
3. Dim the room so that reflections do not hide small dots.
4. Press “Start the test”. The screen goes full screen and black. Change colour with the arrow keys, the space bar, a swipe, or the arrows on screen. A tap or a click hides the controls so that nothing covers the picture.
5. Look at each colour for several seconds, across the whole surface and into the corners. Then come closer and look again.
6. Mark what you see. Choose “Mark a defect”, point at the dot and say what it looks like: dark, bright or coloured. A ring appears around it; point at a ring to remove it.
7. Press “Finish” to see the summary, the map of your marks and the link to share.

Dead, stuck or bright: what you are looking at

Dark pixel (dead pixel)

A dot that stays black on every colour. The pixel receives no power or its transistor has failed. It is most visible on white and on the bright colours. This is the true “dead pixel”, and it is almost never recoverable.

Bright pixel (hot pixel)

A dot that stays white on every colour, including black. All three sub-pixels are permanently on. It is the most noticeable fault, especially in dark scenes, and the one manufacturers tolerate the least.

Stuck pixel

A dot that stays red, green or blue, or a mix of two, whatever the screen shows. One or two sub-pixels are stuck on or off. On a colour that contains the stuck one it disappears, which is why several colours are needed to find it. A stuck pixel sometimes comes back by itself or with the fixer below.

Dust or pixel?

A dead pixel is a sharp little square that never moves and looks the same from any angle. Dust has an irregular shape, often shows a faint shadow next to it, changes when you look from the side, and moves or disappears when you wipe the screen. If the dot is still there after wiping and looks identical on a second run, it is in the panel.

How many dead pixels are acceptable?

No screen maker promises a perfect panel on every model. Most follow a tolerance often called Class II, after an international standard for flat panels. It accepts, per million pixels:

• up to 2 bright pixels,
• up to 2 dark pixels,
• up to 5 stuck sub-pixels.

A Full HD screen has about 2 million pixels, and a 4K screen more than 8 million, so the accepted number grows with the resolution. The test works this out for your screen and tells you whether your count is within that tolerance or above it.

Treat it as a reference point, not as a rule. Some brands promise more, such as no bright pixel at all on their premium ranges, and a few replace a screen for a single faulty pixel. Read the pixel policy in your warranty. On a newly bought screen, remember that a right of return usually does not depend on any tolerance: if you see a fault within the return period, send the screen back.

Can a dead pixel be fixed?

A dark pixel: no. It is a hardware failure.

A stuck pixel: sometimes. A sub-pixel that is stuck can occasionally be freed by making it switch very quickly for a while. That is what the optional fixer on this page does: a small square flashes colours over the pixel for up to 10 minutes. Nobody can promise that it works, and a pixel that comes back can stick again later.

The fixer flashes rapidly, so it is kept small, it never fills the screen, and it must not be used by anyone sensitive to flashing lights. Do not press or rub the screen to “massage” a pixel, as some guides suggest: the pressure can damage more pixels than it frees.

Troubleshooting

The test does not go full screen

Some browsers, and all browsers on iPhone, do not let a page take the whole screen. The test then fills the browser window. Turn a phone sideways and hide the address bar to enlarge the area, and check the remaining edges in a second pass, with the phone turned the other way.

The colours look yellowish or dim

Night light, a blue-light filter, a reading mode or automatic brightness is active. Turn them off for the test. On white, a warm tint over the whole screen is a setting, not a defect.

I see a dot on one colour only

That is typical of a stuck sub-pixel: it disappears on the colours that contain it. Mark it as a coloured dot.

There is a larger stain, not a dot

A cloud, a brighter patch near an edge or a faint image of something that was displayed for a long time is not a pixel fault. The screen test checks uniformity, backlight bleed and image retention.

On my phone, the picture is cut by a notch or rounded corners

That is the shape of the screen. Pixels hidden behind a camera cut-out cannot be tested by any page.

Frequently asked questions

Is anything recorded or sent to TestrHub?

No. The colours are drawn by your browser, and your marks stay on your device. The link to share contains the counts, the positions of the marks and your screen size, and nothing is stored anywhere: whoever opens the link reads the result from the link itself.

Why nine colours and not five?

Black, white, red, green and blue find most faults. Cyan, magenta and yellow light two sub-pixels at once, so a single dead sub-pixel shows as a coloured dot instead of hiding. Grey makes dark and bright dots visible on the same screen.

Is a dead pixel the same as burn-in?

No. A dead pixel is a single dot that never changes. Burn-in, on OLED screens, is a faint ghost of an image that stayed on screen for a long time, and it covers an area.

Will dead pixels spread?

A single faulty pixel normally stays alone. A line of dead pixels, or a cluster that grows, points to a damaged panel or connection and is a reason to claim the warranty.

Can I use this result for a warranty claim?

It helps to describe the problem: the number of faults, their type and where they are. The seller or the manufacturer will apply their own policy and may ask for a photo. The result is your own observation, not a certified measurement.

Does it work on phones, tablets and televisions?

Yes, in any recent browser. On a television, open this page with the TV’s browser or connect a computer to it.