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Dead pixel test

Fill the screen with solid colors to spot dead, stuck and hot pixels, and mark where they are.

Photosensitivity warning

This test fills your screen with solid colors, and every click, tap or key press switches the whole screen to the next one at once, including straight from black to white. If flashing lights or sudden changes in brightness affect you, don't start this test.

To go gently, turn your screen's brightness down first. The colors only change when you ask: auto-cycle stays off unless you turn it on, and holding a key down changes the color once, not repeatedly.

How to run the dead pixel test

Wipe the screen first with a dry microfiber cloth. On a white field, a speck of dust looks exactly like a dead pixel, and you'd waste time chasing it.

Then press Full screen. Only full screen covers every pixel, including the strips behind the tab bar, the address bar and the taskbar. Step through the colors with a click, a tap or the arrow keys, and give each one a slow look: first the whole screen from where you normally sit, then closer, one section at a time. On a high-resolution screen a single pixel is tiny, so a magnifying glass or your phone's camera zoomed in helps.

When you find something, Shift-click it (long-press on a touchscreen) to mark it. A ring stays on the spot so you can compare it under other colors, and the summary lists its position in device pixels and the color that showed it. Click a ring to remove it.

How to read what you see

Every pixel is made of a red, a green and a blue subpixel. A fault is one or more of them stuck on or stuck off, and the color on screen decides whether that shows:

  • Dead pixel: all three subpixels stay off. It's a black dot on white and on bright colors, and invisible on black.
  • Hot pixel: all three stay on. It's a white dot on black.
  • Stuck pixel: one or two subpixels stay on. It shows as a red, green, blue or mixed dot on black, and on any color that doesn't already include that subpixel. Cyan, magenta and yellow each switch one channel off, which singles out a stuck red, green or blue subpixel.
  • Dead subpixel: one subpixel stays off. On white it shows as a colored dot, the color of the other two: a missing red leaves a cyan dot.

Something that looks blurry, sits on top of the image rather than in it, or moves when you wipe the screen is dirt, not a pixel. A faint dot that only shows on one color and fades over minutes is more likely image retention than a fault.

What the browser can and can't tell

A web page can send colors to the screen but can't see the light that comes back, so no browser test can detect a dead pixel on its own. This one shows pure colors, where every channel is either fully on or fully off, and records what you find.

A marked position is where your pointer was, in CSS pixels, multiplied by the device pixel ratio. In full screen the test area is the whole screen, so that's the position from the screen's top-left corner. Outside full screen it's measured from the test area's corner instead, because a page can't reliably tell where its window sits on the screen. Display scaling and browser zoom can move the result by a pixel or two.

Night modes and blue light filters tint white orange and dim the blue channel, which makes blue faults harder to see. Turn them off for the test.

Questions

What is the difference between a dead, a stuck and a hot pixel?

A dead pixel has all three of its red, green and blue subpixels switched off for good, so it stays black and shows up on white. A hot pixel has all three stuck on and shows as a white dot on black. A stuck pixel has one or two subpixels stuck on, so it glows red, green, blue or a mix, and shows best on black.

Why run the test full screen?

Inside a normal page, the browser's tab bar, address bar and your taskbar cover parts of the screen, and the page itself leaves a border around the test area. Faults under any of those go unseen. Full screen fills every pixel with the test color. Safari on iPhone can't make a page full screen, so there the test fills the window and the status bar stays uncovered.

Can a stuck pixel be fixed?

Sometimes. A stuck subpixel occasionally frees itself after running rapidly changing colors over it for a while, or after very gentle pressure through a soft cloth, though pressing can damage the panel and may void the warranty. A dead pixel that gets no power at all rarely comes back. This site does not offer a color-flashing fixer, because full-screen flashing is a seizure risk and the results are hit and miss.

How many dead pixels are acceptable?

That depends on the manufacturer's pixel policy. Many follow the fault classes in ISO 9241-307, which allow a handful of defects on most panels, and some brands promise replacement for a single bright pixel. Policies usually count bright and dark faults separately and care about where they sit, so note the position and the color that revealed each one. The summary lists both.

Do dead pixels spread?

A single dead pixel doesn't make its neighbors fail. If you see new ones appearing over weeks, or a whole line of them, that points to a failing panel or a loose connection rather than isolated pixel faults, and it's worth raising with the seller while the warranty lasts.

Does the test work on phones and OLED screens?

Yes. Tap to move to the next color and long-press to mark a pixel. OLED pixels make their own light, so a dead one is completely black and a stuck one is easy to spot on black. On OLED, also look for faint shapes of the status bar or keyboard on the grey custom color: that is burn-in, a different kind of wear.

Is anything sent anywhere?

No. The colors are drawn by your browser and the marks you make stay on this page until you leave it. Nothing is uploaded, and the only thing kept in the address bar is the custom color you picked, so you can come back to it.