Check any screen for dead, stuck and hot pixels with full-screen colours, test backlight bleed, banding and sharpness, and try the stuck pixel fixer.
Runs in your browser. Nothing to install, and your marks and results stay on this device.
- Go full screen
- Cycle through the solid colours
- Zoom in on any dead or stuck pixel
Full-screen colour test
Nine solid colours that make dead, stuck and hot pixels easy to spot, then extra screens for bleed, banding, uniformity, sharpness and motion.
Click, tap or press the right arrow for the next screen. Press Esc to exit.
Your screen
- Resolution
- Checking…
Your results
Before you start
- Clean the screen with a dry microfibre cloth. Dust looks just like a dead pixel.
- Turn brightness up for the colour screens. Turn it down to about 20 to 50% for backlight bleed.
- Sit straight in front at your usual distance, and look slowly across the whole screen on each colour.
Or jump straight to a screen
Stuck pixel fixer
A small square of rapidly changing colours that can exercise a stuck pixel. It sometimes clears one, with no guarantee, and is very unlikely to help a dead pixel.
Photosensitivity warning. The fixer flashes bright colours rapidly. Do not use it if you, or anyone who can see the screen, has photosensitive epilepsy or is affected by flashing light. Look away while it runs. Press any key, or Stop, to end it at once.
Drag the square over the stuck pixel, or tap where it is. Drag the corner to resize. If you marked a pixel in the test, the square starts there. Leave it running for at least 10 minutes, then check the pixel on black and white.
Keyboard and touch controls
| To | Use |
|---|---|
| Next screen | Click, tap, swipe left, Space, Enter or the right arrow |
| Previous screen | Right-click, swipe right, Backspace or the left arrow |
| Jump to a colour | Number keys 1 to 9 |
| Mark a suspect pixel | Press M, then click or tap the pixel. Click it again to remove the mark |
| Auto-advance on or off | A |
| Hide or show hints | H |
| Show the controls | Move the mouse, or touch and hold the screen |
| Exit | Esc, or Exit in the controls |
How it works
- Go full screen
- Cycle through the solid colours
- Zoom in on any dead or stuck pixel
What the dead pixel test does
A dead pixel test fills your screen with solid colours so faulty pixels stand out: a dark dot on a bright colour is a dead pixel, and a lit dot on black is a stuck or hot pixel. This one also checks backlight bleed, banding and sharpness, lets you mark faults with exact positions, and includes a stuck pixel fixer.
- Works with: monitors, laptops, TVs with a browser, tablets and phones, LCD or OLED.
- Tests: nine solid colours, then bleed, uniformity, banding, sharpness and motion screens.
- Extras: marks with exact pixel positions, auto-advance, a timed fixer, and your screen’s resolution and refresh rate.
- Privacy: the test runs on your device. Your marks and results are never uploaded.
How to do a dead pixel test on your screen
- Wipe the screen with a dry microfibre cloth and turn the brightness up.
- Click Start the dead pixel test. The screen turns black.
- Look slowly across the whole screen, then click, tap, swipe or press the right arrow for the next colour. Keys 1 to 9 jump to a colour.
- If you spot a dot, press M (or Mark in the controls) and click it. Check the same spot on black and on white.
- Press Esc when you are done. Your marks are listed with their positions, and Copy summary copies the details for a warranty claim.
Dead, stuck and hot pixels: what is the difference?
A dead pixel test makes more sense once you know that on most screens each pixel is made of red, green and blue sub-pixels. The ISO 13406-2 standard named three kinds of fault: a hot pixel is always on and white, a dead pixel is always off and black, and a stuck pixel has one or more sub-pixels always on or off.
| What you see | What it is | Can it be fixed? |
|---|---|---|
| A black dot on white and colour screens | Dead pixel | Usually not: it is a hardware fault |
| A red, green or blue dot on black | Stuck sub-pixel | Sometimes, with the stuck pixel fixer |
| A white dot on black | Hot pixel | Sometimes, with the stuck pixel fixer |
| A cyan, pink or yellow dot on white | One dead sub-pixel | Usually not |
| A fuzzy, irregular speck, clearest on white | Dust on or behind the glass | Wipe it off; dust inside needs a service visit |
How many dead pixels are acceptable?
It depends on the maker’s pixel policy. In 2007 most manufacturers rated their screens ISO 13406-2 Class II, which allowed up to 2 hot pixels, 2 dead pixels and 5 sub-pixel faults per million pixels. The standard was replaced by parts of ISO 9241 in 2008, but its limits are still a useful yardstick. Scaled to common resolutions and rounded down:
| Screen | Hot | Dead | Sub-pixel |
|---|---|---|---|
| 1366 × 768, 1.05 million pixels | 2 | 2 | 5 |
| 1920 × 1080 Full HD, 2.07 million | 4 | 4 | 10 |
| 2560 × 1440 QHD, 3.69 million | 7 | 7 | 18 |
| 3440 × 1440 ultrawide, 4.95 million | 9 | 9 | 24 |
| 3840 × 2160 4K, 8.29 million | 16 | 16 | 41 |
Some makers are stricter: Dell’s Premium Panel Exchange replaces an eligible monitor for even one bright pixel. Run the dead pixel test on a new screen the day it arrives and keep the copied summary. In the UK, the Consumer Rights Act 2015 gives you 30 days from delivery to reject faulty goods for a full refund.
How to fix a stuck pixel
The stuck pixel fixer shows a small square of rapidly changing random colours. Drag it over the stuck pixel, or mark the pixel during the test so the square starts there. Fixer makers suggest running it for at least 10 minutes; if the pixel has not changed after an hour, it is unlikely to respond. It sometimes works, with no guarantee, and is very unlikely to revive a dead pixel, which is a hardware fault.
Flashing light can trigger seizures in people with photosensitive epilepsy, most commonly at 3 to 30 flashes a second. The fixer never starts on its own, asks you to confirm and stops at any key. Its square is at most 128 pixels wide, under the flashing area limit in the Web Content Accessibility Guidelines at a normal viewing distance. Slow mode, the default if your device asks for reduced motion, changes colour twice a second, under their limit of three flashes a second.
Backlight bleed, IPS glow and tests beyond the dead pixel test
| Screen | What it shows | What to look for |
|---|---|---|
| Backlight bleed | Light leaking in at the edges of an LCD | Bright patches at the edges on black, with the room dim and brightness at 20 to 50% |
| IPS glow | A glow on IPS panels seen at an angle | Glow that shifts as you move your head, unlike bleed |
| Uniformity 10 to 40% | How even dark greys look | Cloudy patches, darker corners, bands or faint shapes |
| Gradient banding | Ramps of 256 shades per colour | Visible steps or tints in a smooth blend |
| Sharpness and text | One-pixel checkerboards, lines and text | Blur, shimmer or colour fringes at 100% zoom |
| Motion and ghosting | Blocks moving at 480 and 960 pixels a second | A smear trailing behind each block |
OLED pixels make their own light, so OLED screens have no backlight to bleed. They can be more prone to burn-in than LCDs, so look for faint shapes on the grey screens.
Frequently asked questions
What is the difference between a dead pixel and a stuck pixel?
A dead pixel never lights up, so it shows as a black dot on bright screens. A stuck pixel has one or more sub-pixels stuck on, so it shows as a red, green, blue or white dot, most clearly on black.
Can a dead pixel be fixed?
Usually not. A dead pixel is a hardware fault, so the remedy is a warranty claim or a repair. Stuck pixels sometimes clear with a pixel fixer.
Do dead pixels spread?
No, and a dead pixel test is a good way to check for new ones later. One dead pixel does not make its neighbours fail, though new faults can appear as a screen ages or is knocked.
Is a dead pixel covered by warranty?
It depends on the maker’s pixel policy, which sets how many faulty pixels a screen needs before it is repaired or replaced. Policies differ by brand and model, and some are stricter about bright pixels than dark ones, so check yours and keep the summary from the dead pixel test for your claim.
How many dead pixels are acceptable on a new monitor?
It depends on the maker’s pixel policy. Under the old ISO 13406-2 Class II, a Full HD screen could have up to 4 dead and 4 hot pixels, but some premium monitor lines are replaced for a single bright pixel.
Does the dead pixel test work on phones?
Yes. Chrome on Android goes full screen. Safari on iPhone does not let web pages go full screen, so the test fills the browser window instead.
Is the stuck pixel fixer safe to use?
Do not use it if you or anyone watching has photosensitive epilepsy or is affected by flashing light. Otherwise, keep the square small, look away while it runs, and choose Slow for a gentler flash.
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