Screen Test: Dead Pixel and Monitor Test

How to use it

1. Clean the screen. Dust looks like a dead pixel. Wipe the screen with a dry microfibre cloth first.
2. Choose a test and press "Start full screen". The Dead pixels test is selected at the start. It is the one to run first on a new or second-hand screen.
3. Move through the screens. Click, or press Space or →, for the next screen. Press ← to go back and Esc to close. On a phone, tap the screen, and tap its left edge to go back. The help text fades after three seconds so that it does not cover any pixels.
4. Look closely. Check each screen slowly, corner to corner, from about 30 cm. If you find a spot, take a photo and note where it is. It is your evidence for a return.

The screens change only when you ask, so nothing here flashes by itself. The Ghosting test has blocks that move fast. Skip it if moving patterns bother you.

What each test shows

Reading the results

Dead, stuck or just dust? A dead pixel stays dark. A stuck pixel stays lit in one colour, so it shows up on the black screen and on the colours that do not contain it. Dust moves when you wipe it, and it looks soft rather than sharp.

Backlight bleed or IPS glow? Move your head back, or tilt the screen. IPS glow is normal on these panels, and it changes with your position [2]. Backlight bleed is a defect: light leaks through the edges of the panel [2]. Judge both in a dim room at a normal brightness. At full brightness in a dark room, almost every LCD shows some.

Is my refresh rate right? Browsers usually draw one frame for each refresh of the screen, so the frame count here follows the screen [3]. If you see 60 Hz on a 144 Hz monitor, the likely cause is a setting or a cable. On Windows, open Settings > System > Display > Advanced display and choose the rate there [4]. On a Mac, open System Settings > Displays. Safari on an iPhone usually draws 60 frames a second, even on a 120 Hz screen, so 60 there does not mean a fault. A laptop on battery, or a browser with many tabs open, can run below the screen's rate. Variable refresh rate can also lower the reading when little is moving on the screen.

Ghosting or a slow camera? Judge ghosting with your eyes, not with a phone camera. A camera has its own shutter, and it can add trails that are not on the screen.

Should I return it?

It depends on the maker and on the model. Makers set their own limits, and they do not all read the ISO pixel standard the same way [1]. Dell, for example, replaces monitors under its Premium Panel Exchange for one bright pixel during the warranty and tolerates up to 5 dark subpixels on most of them. Its standard monitors allow up to 5 bright pixels or subpixels [5]. Check the policy for your model before the return period ends. Photograph the fault first, on the same screen of this test.

Test a 3D screen

The last test is a 3D picture in side-by-side form: the left half is for the left eye and the right half is for the right eye. On a normal screen you see two nearly identical pictures. The red square sits a little further to the left in the right half, and the blue one a little further to the right. On a 3D monitor or a headset in side-by-side mode, the two become one picture, the red square floats in front of the grid, and the blue one sits behind it.

The Owl3D Shift is a glasses-free 3D monitor that detects a side-by-side picture on its screen and shows it in 3D. Press Start on the Stereo 3D Playback tab in the Owl3D app, then run this test full screen.

Frequently asked questions

How do I test my monitor for dead pixels?

Run the Dead pixels test above, full screen, and go through each colour slowly. A dot that stays dark or stays one colour on every screen is a dead or stuck pixel. Clean the screen first, so that you do not mistake dust for a fault.

Can a dead pixel be fixed?

A stuck pixel sometimes can. Software that flashes colours over the spot can bring it back, though it does not always work [1]. A truly dead pixel usually cannot be fixed, and the panel has to be replaced. This page has no pixel fixer: nothing here flashes, by design.

How many dead pixels are acceptable?

There is no single number. Each maker sets its own limit, and it often differs for bright pixels and dark ones [5]. Look up the pixel policy for your model.

Does this work on a phone or a TV?

Yes, on anything with a browser. Safari on an iPhone has no full-screen mode for web pages, so its bars may stay visible at the edges. Rotate the phone, and check the edges a second time with the bars scrolled away. On a TV, open this page in its browser, or connect a computer.

Why does it show a lower refresh rate than my screen's?

The measurement counts the frames your browser really draws. Check the rate in your system settings, then close other tabs and plug in a laptop. Some cables and ports also limit the rate at high resolution.

Does this test OLED burn-in?

Yes. Use the Backlight bleed test: its dark grey screen and the Dead pixels grey screen show burn-in as a faint shape that stays. Black will not show it. Bright pixels on a black OLED screen are stuck pixels, not burn-in.

Is anything uploaded?

No. Every screen is drawn in your browser. We count which test was started and finished, with no picture and nothing about what you see.