How the test works

First, wipe the screen gently with a soft cloth. Dust and smudges can look like dead pixels – a real one stays in place after wiping.

The whole screen then shows white, black, red, green and blue, one at a time. Tap or click anywhere for the next colour, or use ← Previous colour to go back. The text hides itself after about 2 seconds, so the entire screen is one colour. Nothing flashes – the colour changes only when you tap or click.

Finally, you answer What did you notice? and get a short result with plain-language advice, which you can save as PDF.

Dead pixel or stuck pixel?

Each pixel is made of tiny subpixels – red, green and blue – that mix to make the colours you see.

• Dead pixel – the pixel stays dark. It shows as a black dot on white and other bright colours, but not on black.
• Stuck pixel – one or more subpixels stay lit. It shows as a bright or coloured dot on black – usually red, green, blue or white – and as an odd-coloured dot on some of the other colours.

Each test colour lights different subpixels, so five colours catch faults that one colour would miss.

How to check a monitor for dead pixels

The Resolution card above shows roughly how many pixels your screen has, as width × height (on a Mac with a scaled resolution, it shows the size the Mac draws at). A 3840 × 2160 screen has more than 8 million, so one faulty pixel is tiny. Don’t just glance – search.

1. Look section by section – left to right, top to bottom, like reading a page.
2. On a phone or laptop, bring the screen closer to your eyes. On a large monitor or TV, step up close.
3. Check the corners and edges too.
4. If you find a dot, wipe that spot again. If it moves or disappears, it was dust.

If you find a dead or stuck pixel

• Note where it is and on which colour it shows. A close-up photo helps if you contact the seller.
• Check the return period and the warranty. Policies on pixel defects differ – some replace a screen for one bright pixel, others only above a certain number – so read the manufacturer’s or seller’s terms.
• A stuck pixel sometimes recovers by itself after the screen has been on for a while. A dead pixel usually does not.
• Don’t press on the screen or rub it hard – you can damage the panel. Skip flashing “pixel fixer” videos too. Rapid flashing can trigger seizures in people with photosensitive epilepsy, which is why PeakNits never flashes.

Blotches or darker edges rather than single dots? Try the uniformity test. On OLED, the burn-in test looks for faint shapes left by static images.

More single tests

• HDR brightnessHow bright highlights get, and how much big bright areas dim.
• Black levelTrue black and the darkest shadow detail.
• GradientsStripes in smooth colour ramps – 8-bit or 10-bit.
• ColoursStandard sRGB, Display-P3 or beyond.
• Refresh rateYour Hz right away, plus motion clarity.
• Burn-inFaint shapes left by static images on OLED.
• UniformityPatches, darker edges and backlight bleed.