Dead Pixel Test

Find dead or stuck pixels by cycling fullscreen white, black, red, green, blue, cyan and magenta screens with click or keyboard navigation.

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This test cycles 7 full-screen solid colors so you can spot dead or stuck pixels on your display. A dead pixel stays black no matter what color fills the screen. A stuck pixel stays one fixed color (usually red, green or blue) even as everything around it changes.

Once started, click anywhere (or press the right arrow / spacebar) to move to the next color, the left arrow to go back, and Esc to exit. The test tries to enter fullscreen for the most accurate result, but still works even if your browser can't go fullscreen.

🔒 Private by design: everything runs locally in your browser and never uploaded to any server.

Written and maintained by Last updated

The seven colors in the cycle, and what each one reveals

The sequence is fixed: white, black, red, green, blue, cyan, magenta. The order is not decorative. White is the brightest thing the panel can produce, so a pixel with no power reaching it shows up as an obvious dark speck against it. Black is the opposite test. With the whole screen off, any sub-pixel locked on at full brightness becomes a tiny colored pinprick that is very hard to miss.

The three primaries in the middle isolate one channel each. Fill the screen with pure red and only the red sub-pixels are lit, which means a pixel that fails on green alone looks perfectly normal on the red screen and wrong on the green one. That tells you which channel is broken, not just that something is.

Cyan and magenta are the two extra checks. Cyan drives green and blue and leaves red dark; magenta drives red and blue and leaves green dark. Because each one switches off exactly one channel, a sub-pixel stuck on that channel appears as the wrong color rather than as a slightly brighter dot, and a hue difference is much easier for the eye to catch than a brightness difference.

Cycling through the panel, one color at a time

  1. Click Start dead pixel test. The tool asks the browser for real fullscreen and fills the screen with the first color, white.
  2. Sweep across the panel in bands, corner to corner, instead of staring at the center. Sit close enough that a single pixel is actually resolvable.
  3. Click anywhere, or press the right arrow or spacebar, to move on. The hint strip names the color and your position out of seven.
  4. Press the left arrow, or the ← Previous button in the hint strip, to step back to a color that deserves a second look.
  5. Press Esc, or the Exit (Esc) button, when you are done.

Fullscreen is attempted, then quietly forgiven

Starting the test fires a real requestFullscreen() call on the tool’s own container, with a WebKit fallback, wrapped in a try/catch that swallows any rejection. This matters because the color layer itself is a plain fixed, full-viewport overlay: it does not need the Fullscreen API to work at all. An iframe without a fullscreen permission, or a user who declines the prompt, still gets a usable test.

Real fullscreen is worth having when it is available, though. Browser chrome, the tab strip, the address bar and a scrollbar all sit over parts of the panel you would otherwise never get a flat color onto, and edges are precisely where you want to look. There is also a fullscreenchange listener wired up, so if the browser drops out of fullscreen on its own through F11 or its own exit affordance, the test closes instead of leaving a colored sheet stranded over the page.

Dead, stuck, and telling them apart in two clicks

A dead pixel receives no power. It stays dark on white, on red, on green, on blue, on cyan and on magenta, and vanishes into the background only on the black screen. A stuck pixel is the reverse: it is powered but locked, so it holds one fixed color while everything behind it changes, and it screams on black.

That is the whole diagnostic. Note the position of the dot, then step through the cycle watching only that spot. If it is always dark, it is dead. If it is always the same bright color, it is stuck, and the primary it matches names the offending sub-pixel channel. Both defects are pixel-sized, so this is one of the few checks worth doing with your nose near the glass.

Where this sits among the other panel checks

A dead pixel is a manufacturing defect, but plenty of the things people blame on one are not. If the whole image tears or stutters, that is a frame timing question rather than a pixel question, and the refresh rate test measures it directly. If you are trying to work out what panel you actually bought, What Is My Screen Resolution reads it back from the browser. On a phone or a tablet, an unresponsive patch of glass is a digitizer fault rather than a display fault, which is what the Touchscreen Test is for.

The same “open a page, check the hardware, close the page” pattern covers the Keyboard Tester and the rest of the testers section, and the hardware testers guide walks through which check answers which symptom.

What this test does not do

It finds nothing by itself. There is no image analysis, no camera, no measurement of the panel in software: seven flat colors and your own eyes are the entire mechanism. A defect you do not personally spot is a defect this page will not report, which is why the slow corner-to-corner sweep on each color matters more than the tool does.

It also cannot distinguish a panel defect from dust, a fingerprint, or a speck trapped under the glass. Clean the screen first. A mark that survives a cloth and holds the same color through all seven backgrounds is a real stuck pixel; one that moves or disappears was never a pixel at all.

See it in action

Screenshot of the Dead Pixel Test tool with a display test that cycles seven full-screen solid colours, with the distinction it depends on stated up front: a dead pixel stays black whatever colour fills the screen, while a stuck pixel stays lit in one colour
Dead Pixel Test mid-process: a display test that cycles seven full-screen solid colours, with the distinction it depends on stated up front: a dead pixel stays black whatever colour fills the screen, while a stuck pixel stays lit in one colour.
Diagram: where the work happens on a SysFenix page that has no file input at all: the tool arrives as ordinary JavaScript inside the page, works the answer out on your own device and renders it in place, so the upload, queue and server-side record a typical online tool needs never happen
Where the work happens on a SysFenix page that has no file input at all: the tool arrives as ordinary JavaScript inside the page, works the answer out on your own device and renders it in place, so the upload, queue and server-side record a typical online tool needs never happen.

Frequently asked questions

Which key does what once the color overlay is up?

Right arrow and spacebar both advance to the next color, left arrow steps back one, and Esc ends the test. Clicking anywhere on the color advances too, so the whole cycle can be run from a trackpad without touching the keyboard. The two buttons in the hint strip, Previous and Exit, deliberately stop the click from also advancing, so pressing them does exactly what the label says and nothing else.

Does the cycle stop at magenta, or start over?

It wraps in both directions. Advancing past magenta returns to white, and stepping back from white lands on magenta, so you can go round as many times as you like without restarting. The hint strip names the current color and your position out of seven, so it is always clear where in the sequence you are.

What happens if my browser refuses to go fullscreen?

The test still runs. Real fullscreen is requested once when you start and any rejection is swallowed on purpose, because the colored layer is a fixed full-viewport overlay that does not depend on it. You lose the strip of screen taken up by browser chrome, so maximize the window and inspect those rows separately, but every pixel the overlay does cover is tested exactly as normal.

Will cycling these colors repair a stuck pixel?

No, and this page does not try. There is no rapid flashing repair mode here, only seven steady colors you step through yourself at your own pace. A genuinely dead pixel has no power reaching it and no software can bring it back. A stuck sub-pixel is occasionally coaxed loose by other methods, but nothing on this page attempts that.

Why are cyan and magenta in the list after the three primaries?

Every pixel on an LCD panel is built from one red, one green and one blue sub-pixel. Cyan lights green and blue while leaving red dark, and magenta lights red and blue while leaving green dark, so each one switches off exactly one channel. A sub-pixel stuck on the missing channel then reads as a wrong-colored dot rather than a marginally brighter one, which the eye catches far more easily.

Is one bad pixel enough to return a brand new monitor?

That depends on the manufacturer, not on this tool. Most panel makers publish a pixel policy with a defect count threshold, and many treat a bright stuck pixel more seriously than a dark dead one. Run the full cycle while the retailer's return window is still open, photograph anything you find, and check the policy for your exact model before making the case.

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