How to use the Dead Pixel Test
- Clean the screen, set brightness to your usual level and turn off night mode or blue-light filters.
- Click Start full-screen test. Click, press Space or the arrow keys to change colours, and Esc to exit. Auto-cycle is optional.
- Look for bright dots and bleed on black, and dark or coloured dots on white and solid colours. Note the position of any defect.
- For a suspected stuck pixel, try the flashing fixer for 10–20 minutes, then copy the summary for the seller.
Dead, hot and stuck pixels
A dead pixel stays black on every colour and is usually a failed transistor that cannot be repaired. A hot pixel stays lit white on black. A stuck pixel is frozen on a red, green or blue sub-pixel and can sometimes be revived by rapid colour flashing. ISO 9241-307 grades pixel faults, and brand "zero bright dot" guarantees refer to it, so check the return policy before you buy.
Checking backlight bleed and uniformity
In a dark room, switch to pure black and 10–20% grey and look for bright patches at corners and edges (bleed) or a greyish glow (IPS glow, which fades when viewed straight on). On 50% grey, look for visible tint shifts or dark corners, which reveal brightness and colour uniformity.
What gradients and sharpness patterns reveal
Grey and RGB gradients show banding and posterisation, common on 6-bit panels or with wrong colour settings. If the 1px checkerboard or fine lines show moiré, flicker or blur, scaling is not 100%, the resolution is not native, or the panel has PWM or response issues.
Frequently asked questions
Is an online dead pixel test accurate?
Full-screen solid colours are the method manufacturers and reviewers use. Accuracy depends on staying in full screen, disabling colour filters and looking carefully. Check once in a dark room and once in normal light, and confirm suspected spots with a magnifier or phone camera.
Can the flashing fixer repair a stuck pixel?
It sometimes helps stuck pixels but cannot fix a truly dead pixel. The fixer flashes colours rapidly, so do not use it if you are sensitive to flashing light or have photosensitive epilepsy, and look away while it runs.
How many dead pixels justify a return?
It depends on the brand and retailer. Some promise zero bright pixels; others allow a few defects according to ISO 9241-307 classes. Send photos and positions to the seller within the return window.
Does it work on a phone?
Yes. Tap Start and the page tries to go full screen; tap to change colours. Some browser address bars cover the top edge, so rotate to landscape or scroll to hide the bar.
Why is the resolution smaller than the spec sheet?
Web pages read CSS pixels. Physical pixels equal the CSS resolution multiplied by the device pixel ratio (DPR), for example 1440×900 × 2 = 2880×1800. The tool lists both.