Dead Pixel Test

Fill your whole screen with solid colors and look for pixels that stay dark, bright or colored.

Start the test, then click or press Space / → for the next color, ← to go back and Esc to exit.

Or pick a color

How to find dead pixels

Clean the screen first — dust looks like a dead pixel.
Raise brightness to maximum, start the test and step through every color.
On white, a dead pixel shows as a black dot. On black, a stuck pixel shows as a bright dot.
On red, green and blue, a sub-pixel that is stuck off or on shows as a dot of the wrong color.

Dead, stuck and hot pixels

Dead pixel: always black, never lights. Stuck pixel: always one color (red, green, blue). Hot pixel: always white. Stuck pixels can sometimes be revived by gently massaging the spot or running a flashing-color tool; dead pixels usually cannot.

FAQ

Does this work on phones, laptops and TVs?

Yes. Open this page in any browser on the device and use the full-screen mode. On a TV, use its built-in browser or cast the page.

How many dead pixels are acceptable?

It depends on the manufacturer’s policy (often described by an ISO 9241-307 class). Check your warranty terms before returning a display.

What is backlight bleed?

Light leaking at the edges, visible on the black screen in a dark room. It is a panel quality issue, not a dead pixel.

How to run the test

Wipe the screen with a dry microfibre cloth. A speck of dust or a fingerprint looks very much like a dead pixel, and it is the most common false alarm.
Turn the brightness to maximum and, in a dim room, press Start full-screen test. The page asks the browser for full screen and covers everything with one colour.
Look at the screen slowly, section by section, from a normal viewing distance and then from close up. Click, or press Space or the right arrow, to move to the next colour. The left arrow goes back, and Esc ends the test.
Use the colour picker to test any shade of your own. Choosing a colour opens it full-screen straight away.

If your browser refuses full screen, the colour still fills the visible page, so you can test with the browser window maximised. Leaving full screen by any route also closes the test.

The nine colours and what each one reveals

The built-in sequence has nine colours, in this order: black, white, red, green, blue, yellow, cyan, magenta and mid-grey. It starts at black and wraps around after grey, so you can keep clicking in a loop. Each screen is useful for a different fault:

Black: any dot that glows is a stuck-on pixel. It is also the best screen for spotting backlight bleed and uneven glow at the edges and corners of an LCD.
White: any dot that stays dark is a dead pixel. Look for dim patches or a colour tint in one area too.
Red, green and blue: each screen lights only one of the three sub-pixels that make up every pixel. A speck that stays dark on red but lit on the others shows one sub-pixel is stuck off. A speck that is bright on a screen where it should be dark is stuck on.
Yellow, cyan and magenta: these light two sub-pixels at once. A single flawed sub-pixel then appears as a dot of a shifted colour, which can be easier to see than on the pure primaries.
Mid-grey: a flat grey makes uneven brightness, vertical bands, smudgy clouding and faint image retention easier to see.

Dead, stuck and partly stuck pixels

Every pixel is made of a red, a green and a blue sub-pixel. If all three are permanently off, you get a black dot that shows up on white. If one or more are permanently on, you get a coloured dot that shows up on black. A pixel that is always white has all three stuck on. Because the cause is a sub-pixel, a "stuck red pixel" is really one stuck red sub-pixel, and it will vanish on a screen where red is not displayed in that area.

Common uses

Buying a used or refurbished monitor, phone or laptop: run the whole sequence before you pay, or within the return window.
Checking a new screen on arrival: a fault found on day one is much easier to resolve than one found months later.
Diagnosing a spot you noticed: step through the colours to see if it changes with the colour (a sub-pixel), stays black (dead) or disappears (dirt or a pressure mark).
Checking a TV or projector: open the page in the built-in browser, or cast it, and use the same sequence.

Tips and limits

Test at the display's native resolution. If the operating system scaling is unusual, a bright speck can be a rendering artefact rather than a fault in the panel.
Watch for tiny dots that only show on one colour. Zooming in with your eyes is not enough for small panels, so lean close or use a magnifier.
The page only fills the screen. It cannot measure colour accuracy, response time or brightness, and it does not scan automatically; you need to look yourself.
Other pixel flaws exist that solid colours will not catch, such as image retention, which only appears after a static image has been displayed for a long time.