Dead pixel test
The dead pixel test fills your screen with one solid color at a time, so dead and stuck pixels stand out. No install needed.
- Black
- White
- Red
- Green
- Blue
- Gray
In full screen, tap the right side or press → or Space for the next color, and tap the left side or press ← to go back. Press Esc or Exit to leave.
Runs in your browser. Test data stays on your device.
- Colors checked
- –
- Rendering resolution
- –CSS size × pixel ratio
- Screen in CSS pixels
- –The size web pages see
- Device pixel ratio
- –Device pixels per CSS pixel
- Color depth
- –Bits per pixel
- Viewport
- –Visible page area in CSS pixels
How to use the dead pixel test
- Wipe the screen with a dry microfiber cloth. A speck of dust looks just like a dead pixel.
- Click Start dead pixel test. The screen fills with black.
- Look over the whole screen from your usual distance, then from closer up. Check the corners and the edges too.
- Tap the right side of the screen, or press → or Space, for the next color. Tap the left side or press ← to go back. The colors run black, white, red, green, blue and gray, and after gray the sequence starts again.
- Press Esc or click Exit when you are done.
Nothing changes until you ask for it. The buttons and the cursor fade out after about 2 seconds without input (4 seconds while the first-time hint is on screen), so they cover no pixels. Move the mouse or tap to bring them back; a tap also changes the color. The test also closes when you switch to another tab.
What the results mean
You judge the screen by eye. A faulty pixel stays in the same place on every color, and each type shows most clearly on a different one.
| What you see | What it means | What to do |
|---|---|---|
| A dot that stays black on every color | Dead pixel: all three sub-pixels are off. It shows most clearly on white; on black it disappears. | Wipe the spot, then follow the steps below. |
| A dot that stays white on every color | Hot pixel: all three sub-pixels are lit. It shows most clearly on black; on white it disappears. | Wipe the spot, then follow the steps below. |
| A dot that stays one color, such as red, green or blue | Stuck pixel: one or two sub-pixels are lit all the time. Black and the other colors show it. | Note where it is. It sometimes recovers on its own, but there is no guarantee. |
| A dot that is dark on one color only | Dead sub-pixel: one sub-pixel never lights. On its own color the dot is dark, and on white it looks cyan, magenta or yellow. | Wipe the spot, then follow the steps below. |
| A speck that moves or wipes away | Dust or a smudge, not a pixel. | Wipe the screen and look again. |
| Patchy brightness or bright edges on gray | Uneven backlight, not a pixel fault. | Check it with the backlight bleed test. |
If a dot stays in place on every color, it is a hardware fault:
- Take a photo of the dot on a solid color. It helps with a return or a warranty claim.
- New screen? Check the store’s return period first. A return or an exchange is often quicker than a warranty claim.
- Warranty: manufacturers publish a pixel policy that says how many faulty pixels count as a defect. Some replace a screen for one bright pixel, others allow a few. Look up the policy for your model.
- Do not press on the screen or rub the spot hard. It can damage more pixels.
The cells next to the test show what your browser reports. Colors checked counts the colors you have stepped through in this run, not whether you looked at each one. Rendering resolution is the screen size in CSS pixels times the device pixel ratio, the resolution your browser draws at. A pixel ratio of 2 means each CSS pixel is drawn with 2 × 2 device pixels. The rendering resolution equals the panel’s native resolution only at 100% browser zoom with the display in its native mode. Color depth is the value your browser reports in bits per pixel: 24 bits means 8 bits for each of red, green and blue. It is not a measurement of the panel, and many browsers report 24 even for a 10-bit screen.
Dead pixel test not working?
The test asks for no permission, so it has few ways to fail.
Full screen does not start
The test asks the browser for real full screen when you click Start dead pixel test. If the browser refuses, for example inside an embedded frame, the test fills the page with a fixed layer instead. The colors still cover the page, but the browser bars stay on screen and the pixels under them are not tested. On a computer, press F11 (Windows and Linux) or Ctrl + Cmd + F (Mac) to hide the bars, then run the test.
The test covers only the page on an iPhone
Safari on the iPhone puts only videos into full screen, so there the test is always a layer over the page and the browser bars stay visible. Turn the phone sideways to hide most of them.
The color does not change
Tap the right half of the screen, or press →, ↓, Page Down or Space, for the next color. Tap the left half, or press ←, ↑, Page Up or Shift + Space, to go back. A key held down does not repeat, so press it again for each step. Keys held with Alt, Ctrl or Cmd are handled by the browser, so Alt + ← still goes back in your history, not to the previous color. The arrow buttons at the bottom of the screen do the same.
The test closes by itself
The test closes when you press Esc or Exit, when the browser leaves full screen, and when the page is hidden, for example when you switch to another tab. Click Start dead pixel test again for a new pass from black. The color counter starts again from 1.
Colors look tinted
The test draws exact color values, but the system can still change what reaches your eyes. Turn off Night Light on Windows, Night Shift and True Tone on Apple devices, and eye-comfort or reading modes on Android. These modes shift white and gray toward warmer tones, which makes a faint dot harder to judge. Check again at your usual brightness.
The resolution shown looks wrong
The rendering resolution is the screen size in CSS pixels times the pixel ratio, so zoom and display scaling change it. Press Ctrl + 0 (Cmd + 0 on a Mac) to reset the page zoom, and check the display scaling in your system settings. A scaled mode on a Mac or a lowered resolution on a phone also gives a lower figure than the panel’s native one.
How we measure
The test measures nothing itself: it paints the whole screen in one exact color at a time, #000000, #ffffff, #ff0000, #00ff00, #0000ff and #808080, and you judge the pixels by eye. The cells come from the browser: the screen size from screen.width and screen.height, turned to match how you hold the device, times devicePixelRatio for the rendering resolution, plus screen.colorDepth and the size of the window. The system can still change colors (Night Light, color filters, a color profile), and a browser cannot read the panel’s own pixels, so only you can confirm a faulty one. The Colors checked counter shows which colors you stepped through, not whether you looked at each.
Frequently asked questions
How do I check a screen for dead pixels?
Wipe the screen, click Start dead pixel test and step through the six colors in full screen. Look for a dot that stays in the same place on every color. Check from your usual distance and from close up, and look at the corners and edges as well. A speck that wipes away or moves was dust, not a pixel.
What is the difference between a dead, hot and stuck pixel?
A dead pixel stays black because all three of its sub-pixels are off. A hot pixel stays white because all three are lit. A stuck pixel stays one color, such as red, green or blue, because one or two sub-pixels are lit. The test shows each type on the color where it stands out most.
Can a dead pixel be fixed?
Usually not. A dead or hot pixel is a hardware fault that software cannot repair. A stuck pixel sometimes recovers on its own, but there is no guarantee. If the screen is new, a return or exchange is often quicker than a warranty claim. Otherwise check the warranty before you try anything on the panel.
How many dead pixels are acceptable?
There is no single number, because each manufacturer sets its own pixel policy and it can differ between product lines. Some policies treat bright pixels more strictly than dark ones. Before you contact support, note where each faulty pixel sits and which colors show it, and have the model, a count and a photo of each ready.
Does the dead pixel test work on phones, tablets and TVs?
Yes, in a current browser on a computer, phone or tablet. On a touch screen, tap the right half for the next color and the left half to go back. On an iPhone the test covers the page instead of using real full screen, so the browser bars stay visible. A smart TV works if its browser opens the page.
Does the screen flash during the test?
No. The color changes by one step only when you tap, click or press a key, and a held key does not repeat. Going from black to white is still a sharp change in brightness, so lower the brightness first if bright screens bother you, and press Esc to leave at any time.