1. Full-screen color test
Click a color or the start button. In the test, click, tap, press Space or → for the next color and ← for the previous one. Press Esc to exit.
2. Stuck pixel flasher (optional)
Photosensitive seizure warning. The flasher shows a small square that changes color repeatedly. Flashing light can trigger seizures in people with photosensitive epilepsy. Do not use it if you or anyone who can see the screen has epilepsy or a history of seizures, and stop at once if you feel unwell.
The rate is capped at 3 flashes per second, the limit used by WCAG 2.3.1. This may not fix your pixel; there is no guarantee it will work.
About this tool
A dead pixel test fills the whole screen with one solid color at a time. On a uniform background, a single faulty pixel stands out as a dot that does not match its neighbours. This page cycles through black, white, red, green and blue, with cyan, magenta, yellow and mid gray as optional extras, and includes a slow flasher for pixels that appear stuck on one color. It runs in your browser and works on monitors, laptops, TVs with a browser, tablets and phones.
How to test a monitor for dead pixels
- Clean the screen first. Dust and specks look very like dead pixels. Wipe the screen gently with a dry microfiber cloth, following the manufacturer's cleaning advice.
- Set the display to its native resolution and turn off night-light or blue-light filters, which tint white and can hide colored dots.
- Click Start full-screen test. The browser asks to go full screen. If it cannot, the page covers the whole browser window instead; press F11 or your browser's full-screen command for the best result.
- Step through every color with a click, Space or the arrow keys. Look across the whole screen, section by section, from a normal viewing distance and then up close.
- Check suspicious spots with a magnifier. A magnifying glass or a phone camera's zoom shows whether a dot is one pixel, a single red, green or blue subpixel, or dirt on the surface. Dirt usually moves or smears when wiped; a pixel fault does not.
- Note the position and color of anything you find, and take a photo if you may need to make a warranty claim.
Dead, stuck and hot pixels
On a typical LCD, each pixel is made of red, green and blue subpixels that let more or less light through. Faults are usually described by what you see:
| Term | What you see | Best background to spot it |
|---|---|---|
| Dead (dark) pixel | A black dot that stays dark whatever the screen shows | White, and the bright colors |
| Stuck pixel or subpixel | A dot stuck on one color, such as red, green or blue | Black, and the other primary colors |
| Hot (bright) pixel | A dot that stays lit white | Black |
These names are not used consistently. Some manufacturers call any defective pixel a dead pixel or a stuck pixel, and use "bright dot" and "dark dot" instead. That is why the test cycles through several colors: a pixel that is permanently lit is invisible on white, and a dark one is invisible on black. Photographers also talk about hot pixels in camera sensors, which a screen test cannot check.
What a stuck pixel flasher can and cannot do
A flasher rapidly changes the color of a small area. The idea is that repeatedly driving a stuck subpixel on and off might free it. Online claims about how often this works vary widely, and there is no reliable evidence that it fixes a given pixel. A dead pixel, one that never lights, is generally treated as a hardware fault that software cannot repair. Try it if you like, but expect that it may change nothing:
- Read the seizure warning above the flasher. This flasher is capped at 3 flashes per second, the threshold in the WCAG 2.3.1 Three Flashes or Below Threshold success criterion, where a flash is a pair of opposing changes in brightness. Some other flasher tools run much faster.
- Drag the square over the stuck pixel with a mouse or finger, or nudge it with the arrow keys (hold Shift for 10-pixel steps).
- Leave it running for a while, then go back to the full-screen colors to check. If nothing changes, stop and look at warranty options instead.
- Do not press hard on the screen. Pressure methods suggested online can damage a panel and may not be covered by a warranty.
Checking warranty and return policies
Pixel faults are often handled by a specific dead pixel or pixel defect policy rather than the general warranty, and many policies only cover a panel with more than a set number of faulty pixels, or faults in certain places. Some manufacturers describe their thresholds using the pixel-fault classes of the ISO 9241 ergonomics series. The relevant part, ISO 9241-307, replaced the older ISO 13406-2. Policies differ between brands, models and countries, so read the exact policy for your model on the manufacturer's support site, and check the retailer's return window, which may be easier to use than a warranty claim. Test a new screen as soon as it arrives.
Common mistakes
- Testing only on white. A stuck red subpixel can blend into white. Check every color, especially black.
- Testing in a scaled browser window. If the page does not cover the whole screen, the edges and corners go unchecked. Use full screen.
- Mistaking image retention for a stuck pixel. A faint ghost of a previous image that fades over time is not a pixel fault.
- Confusing backlight bleed with faulty pixels. Light leaking at the edges of an LCD on a black screen is a separate issue from individual pixel faults.
Use cases
Run this test when you unbox a new monitor, laptop or phone, before buying a second-hand screen, after moving or shipping a display, and when you notice a dot that will not go away. For other display and color checks, the Aspect Ratio Calculator helps you work out screen dimensions, the Color Converter translates between HEX, RGB and HSL, and the Contrast Checker tests text and background color pairs.
Frequently asked questions
Yes. Open this page in the phone or tablet browser and start the test. Tap the screen to move to the next color and use the Exit button to leave. Some mobile browsers do not allow full screen, in which case the page fills the browser window, so check the area under the address bar separately.
There is no established answer. Advice online ranges from a few minutes to several hours, and none of it is backed by reliable evidence. A sensible approach is to run it for a short while, check the pixel on the full-screen colors, and stop if nothing has changed rather than leaving it flashing for long periods.
A single faulty pixel is usually an isolated defect and does not by itself cause neighbouring pixels to fail. If you see more faulty pixels appearing over time, or lines and patches rather than single dots, that suggests a different fault with the panel or its connections, and it is worth contacting the manufacturer.
Manufacturing tolerances mean that a small number of pixel faults can occur, and many manufacturers do not treat a single faulty pixel as grounds for replacement. Others offer a zero bright-dot or zero-defect policy on some models. Check the specific policy for your model and the retailer return window as soon as you find it.
A pixel stuck with only its red subpixel lit looks red on black, but on a red background it matches its neighbours, and on white it can be hard to see. That is expected. Write down which colors show the dot, because it tells you which subpixels are affected and helps when describing the fault for a warranty claim.
Yes, the full-screen colors show faulty pixels on any display type. OLED pixels produce their own light, so black should look completely dark, which makes a lit pixel easy to spot. A faint shape that remains after a static image was shown for a long time is image retention or burn-in, not a single faulty pixel.