Screen Test and Dead Pixel Test
Check a new or used monitor, laptop, TV or phone for dead pixels, backlight bleed, banding and blur. Every test runs full screen in your browser.
Choose a test
- Any colour #2F5BEAFill the screen with a colour of your choice.
In full screen: click or press → for the next screen, ← to go back, H to hide the bar, Esc to exit.
Screen details
All tests run in your browser. Nothing is sent anywhere.
Photosensitivity warning
This test flashes bright colours rapidly. Do not use it if you are sensitive to flashing light or have epilepsy, and do not look directly at the flashing square.
How to test your screen
- Clean the screen first: a speck of dust can look just like a dead pixel.
- Press Start dead pixel test. The page goes full screen and fills it with a single colour.
- Look over the whole screen from a normal distance, then click, tap or press → to move to the next colour. A dot that stays black, white or one colour on every screen is a faulty pixel.
- Try the other tests for bleed, banding, sharpness, motion and touch, and press Esc to exit at any time.
What each screen test reveals
Whether you have just unboxed a new monitor, are buying a used laptop or want to check a phone screen, a few minutes with these tests show problems that are easy to miss in everyday use. Everything runs full screen in your browser, so it works on computers, tablets, phones and smart TVs with a browser.
Dead and stuck pixels
A dead pixel stays black on every colour and is most visible on white. A stuck pixel is stuck on red, green or blue and shows on black and on the other colours. A hot pixel stays white and stands out on black. Go through all nine colours, because some faults only show on one of them. Many manufacturers replace a monitor only when it has several faulty pixels, so check the warranty policy and test new screens within the return period.
Stuck pixel fixer
Stuck pixels can sometimes be revived by flashing them rapidly. Drag the flashing square over the stuck pixel and leave it running for 10 to 20 minutes, or longer. It does not help dead pixels, which have no power at all, and it does not work every time, but it is harmless to try. Please read the photosensitivity warning first.
Backlight bleed and uniformity
On LCD screens, light can leak around the edges. Darken the room and look at the black and dark grey screens: bright patches at the corners are backlight bleed, a glow that changes with your viewing angle is IPS glow, and cloudy patches are uneven backlighting. A little bleed is normal; large bright areas are worth reporting. OLED screens have no backlight, so watch instead for uneven grey or faint banding.
Gradients and levels
Smooth gradients should not show visible stripes. Strong banding or colour tints in the grey ramp point to a low-quality panel, wrong colour settings or aggressive image processing. The black and white level screens show whether you can see the darkest and brightest shades; adjust brightness and contrast until most squares are visible.
Sharpness, motion and touch
The 1-pixel line patterns should look like an even grey from a distance and like fine lines up close; flickering or moiré means the display is not running at its native resolution. The circles should be perfectly round. The motion test shows how blurry moving objects look and whether trails appear behind them. On phones and tablets, draw over every square of the touch test to find areas that do not respond. The screen details show the native resolution, scaling and measured refresh rate, useful for confirming that a 120 or 144 Hz screen really runs that fast.
Frequently asked questions
How do I check my screen for dead pixels?
Clean the screen, press Start dead pixel test and look closely at each full-screen colour. A dot that stays black on white, or one colour on black, is a dead or stuck pixel. Check all nine colours because some faults show on only one.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel gets no power and always looks black. A stuck pixel is stuck on one colour, usually red, green or blue, and is most visible on black. Stuck pixels can sometimes be fixed; dead pixels usually cannot.
Can a stuck pixel be fixed?
Often, yes. Run the stuck pixel fixer over the pixel for 10 to 20 minutes, or longer. Gently massaging the spot with a soft cloth while the screen is off also helps sometimes. If neither works, contact the manufacturer about the warranty.
How do I test for backlight bleed?
Turn the brightness up, darken the room and open the Uniformity test. Bright patches near the edges or corners of the black screen are backlight bleed. Look straight at the screen from a normal distance, because viewing from an angle exaggerates it.
Is this screen test safe for my display?
Yes. The tests only show colours and patterns, just like any web page. Only the stuck pixel fixer flashes rapidly; it is safe for the screen but not for people sensitive to flashing light, so read the warning first.