How to use the dead pixel test
- Prepare the screen. Wipe it gently with a dry microfibre cloth so dust is not mistaken for a pixel fault, set brightness to maximum, and switch off night mode, blue-light filters and auto-brightness.
- Press Start full-screen test. The screen fills with black. Look slowly across the whole area from about arm's length, then move closer to any spot that looks wrong.
- Click, tap or press → to step through black, white, red, green, blue, cyan, magenta, yellow and 50% grey, then the pattern screens. Press ← or swipe right to go back, and Esc or swipe down to exit. You can also jump straight to one screen with the coloured buttons, or choose Auto-advance to cycle hands-free.
- For backlight bleed and clouding, dim the room lights and look at the black and dark grey screens. For banding, look at the gradient screens. For sharpness and scaling, look at the checkerboard and grid.
- On a phone or tablet, press Start touch test and draw across every part of the screen. Squares that never fill in point to dead touch zones.
Dead, stuck and hot pixels: how to tell them apart
Each pixel on an LCD or OLED panel is made of red, green and blue sub-pixels. Different faults show up on different backgrounds, which is why the test uses several solid colours:
| Fault | What you see | Best screen to spot it |
|---|---|---|
| Dead pixel | A dot that stays black whatever the colour | White, red, green, blue |
| Stuck pixel | A dot stuck on red, green, blue or a mix such as cyan | Black, plus the colours it does not match |
| Hot (bright) pixel | A dot that stays white | Black |
| Partial sub-pixel fault | A dot that looks wrong on only one or two colours | Red, green and blue in turn |
Dust or a pixel? Dust and specks sit on top of the glass: they usually look grey and soft, they stay dark on every colour, and they move or vanish when wiped. Shine a torch at an angle or look from the side: a speck casts a slight shadow or shifts relative to the pixels, while a real pixel fault stays exactly in the pixel grid and keeps a sharp, square shape. Hide the mouse pointer too; the test hides it automatically after a moment.
Backlight bleed, clouding, banding and uniformity
LCD monitors are lit from behind, and some light can leak around the edges. On the black screen in a dark room, bright patches along the edges or in the corners are backlight bleed; uneven blotches in the middle are clouding. A small amount is common on LCD panels, especially IPS panels, which also show a silvery "IPS glow" that changes when you move your head (bleed does not). Take a photo with your phone only if it matches what your eyes see, as phone cameras exaggerate bleed. OLED screens have no backlight, so they cannot bleed, but on the dark grey screen they may show faint vertical bands or a slight tint, and on the 50% grey screen any panel can reveal dirty-screen effect or tinted corners.
The gradient screens should change smoothly from dark to light. Visible steps or stripes are banding, which can come from the panel, a low colour depth, or image processing in the display or graphics driver. The checkerboard alternates single pixels; on a sharp, correctly scaled display it looks like an even grey texture, while ripples or moiré usually mean the operating system is scaling the picture or the display is not running at its native resolution.
Screen information and refresh rate
The Your screen panel shows the screen size in CSS pixels as the browser reports it, the device pixel ratio, an estimate of the physical resolution (CSS size × pixel ratio), the colour depth and the colour gamut the browser reports. The refresh rate is measured by timing the browser's animation frames for about a second. It reflects what the browser is drawing at right now: power saving, battery mode, a browser frame-rate cap or a monitor connected to a different port can all show a lower number than the panel's maximum, so compare it with your display settings.
What to do if you find a dead or stuck pixel
- New device: check the retailer's return window and the manufacturer's warranty straight away. Return periods and pixel policies vary by shop, brand and country; many manufacturers only replace a panel when the number or position of faulty pixels exceeds their own published limit, while some offer a zero-bright-pixel guarantee.
- Document it: note the colour screens where the fault is visible and take a close-up photo.
- Stuck pixels may recover: a stuck pixel is still powered and sometimes responds to rapid colour changes. The optional fixer above flashes a small square over it for up to 10 minutes. It may help or it may not, and it cannot revive a dead (black) pixel. Some people also try very gentle pressure through a soft cloth, but pressing on a panel can cause more damage, so we do not recommend it.
Checking a whole setup? Try the keyboard tester, the mouse test or the speaker test, or see all device tests.
Privacy: the test runs entirely in your browser. No pictures of your screen are taken and nothing is uploaded; only your auto-advance choice is remembered in this browser's local storage.
Frequently asked questions
How do I check my monitor for dead pixels?
Clean the screen, set brightness to maximum, press Start full-screen test and look carefully at each solid colour. A dot that stays black on white or colour screens is a dead pixel; a dot that stays coloured or white on black is a stuck or hot pixel.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel gets no power and stays black. A stuck pixel has one or more sub-pixels stuck on, so it shows a constant red, green, blue or mixed colour. Stuck pixels can sometimes recover; dead pixels rarely do.
Can a dead pixel be fixed?
A truly dead pixel usually cannot be fixed by software. A stuck pixel sometimes responds to rapidly changing colours, which is what the optional fixer does, but there is no guarantee. If the device is new, a return or warranty claim is the reliable fix.
How do I test for backlight bleed?
Turn the room lights off, wait a minute for your eyes to adjust, set brightness to around the level you normally use and look at the black screen. Light leaking from the edges or corners is backlight bleed; patches in the middle are clouding.
Does the dead pixel test work on phones, iPads and TVs?
Yes. It works in any modern browser. On iPhone, Safari does not allow web pages to go fully full screen, so the test fills the browser window; hide the toolbars by scrolling or use landscape for the largest area. On a smart TV, use the TV's browser or cast the page.
How can I test my touch screen?
Press Start touch test and slide your finger over the whole screen. Every square you touch fills in and the number of fingers detected at once is displayed. Squares that never fill in, or lines that break as you draw slowly, suggest a dead zone in the digitiser.
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