Dead Pixel Test
Fill your screen with solid colours, one at a time, to reveal dead pixels, stuck pixels and uneven backlight.
This test only paints solid colours on your screen. Nothing is sent anywhere.
In fullscreen: click or press → for the next colour, ← for the previous, Esc to leave.
What this tool does
A dead pixel test fills your whole screen with one flat colour at a time. A pixel that is permanently off shows as a dark dot on white, and a pixel stuck on shows as a bright dot on black. Running through red, green, blue, black and white shows most panel faults. This test does it fullscreen in your browser.
Paints the whole test area one solid colour at a time - black, white, red, green, blue, yellow, cyan, magenta and grey - and goes fullscreen so nothing else is on the screen.
Tells you which fault each colour is there to reveal, and lets you step through the colours with a click or the arrow keys.
How to use it
- Clean your screen with a soft dry cloth so dust is not mistaken for a pixel fault.
- Press Start fullscreen test.
- Look carefully over the entire screen on each colour, including the corners and edges.
- Click or press the right arrow for the next colour; press the left arrow to go back.
- Note any dots, patches or lines and which colour showed them, then press Esc to leave. Use Copy checklist for a summary of what to look for.
Why a solid colour test works
Cycles through nine solid colours, and tells you which fault each colour is there to reveal, rather than just flashing colours with no guidance. A single faulty pixel is easy to miss on a busy picture and obvious on a flat field of the right colour.
Each screen pixel is made of red, green and blue sub-pixels. A stuck pixel shows a fixed colour on every background, and a dead pixel stays black. Black and white show those at their clearest, and red, green and blue reveal individual sub-pixels that are stuck.
Why we built it
We built the dead pixel test to cycle through nine solid colours and tell you which fault each colour reveals. Check the display details with the screen resolution checker and test other hardware with the keyboard test.
Handy alongside this: the Badge Maker.
Who this tool is for
- People checking a new monitor, laptop or phone
- Buyers inspecting a second-hand screen
- Repair technicians
When to use it
- When you receive a new monitor, laptop, tablet or phone, within the return period.
- Before buying a used or refurbished display.
- After a screen has been knocked or pressed.
- When you notice a persistent dot or patch and want to know what it is.
What each colour reveals
| Colour | What to look for |
|---|---|
| Black | Bright dots that are stuck on, and backlight bleed at the edges. |
| White | Dark dots that are dead, plus dirt and uneven brightness. |
| Red, green, blue | Dots that are not the right colour - stuck sub-pixels. |
| Yellow, cyan, magenta | Colour patches or tinting across the panel. |
| Grey | Banding, vertical lines and uneven panel areas. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| A speck that does not light up | Dust or a hair on the surface, not a pixel. | Wipe with a soft dry cloth and look again. |
| Fullscreen does not start | The browser blocked fullscreen, or a policy forbids it. | Click the button again, or use your browser's F11 fullscreen. |
| Dot is the same colour on every background | A stuck pixel. | Some can be freed by gentle pressure or a pixel-flashing video; others cannot. |
| Dot stays black on every colour | A dead pixel, which is a hardware fault. | Check the warranty policy for your panel. |
| Glow at the corners on black | Backlight bleed, common on LCD panels. | Compare in a dark room - mild bleed is usually accepted. |
Assumptions and limitations
- It cannot tell a dead pixel from a speck of dust; clean the screen first.
- OLED panels do not have a backlight, so backlight bleed does not apply to them.
- Your own eyesight and ambient light affect what you can see; test in a dim room for black.
- Whether a fault is covered by warranty depends on the maker's pixel policy, which this page cannot know.
Frequently asked questions
How do I test my screen for dead pixels?
Press Start fullscreen test, then step through black, white, red, green and blue, looking over the whole screen on each. Any dot that does not match the colour is a fault.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel is permanently off and shows black on every background. A stuck pixel is permanently on in one colour, so it shows as a bright coloured dot.
Can a stuck pixel be fixed?
Sometimes. Stuck pixels can occasionally be freed by gentle pressure or by running a pixel-refresh video, while dead pixels are a hardware fault and cannot be fixed.
Why do I need to test on several colours?
A faulty pixel is only visible against a background that contrasts with it. Black shows stuck-on pixels, white shows dead ones, and red, green and blue show stuck sub-pixels.
Is a single dead pixel covered by warranty?
It depends on the manufacturer's pixel policy, and many accept a small number before replacing a screen. Check the warranty terms for your model.
What is backlight bleed?
Light leaking around the edges or corners of an LCD panel, most obvious on a black screen in a dark room. OLED panels do not have it.