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Device tests

Dead pixel test

The test fills the whole screen with one colour at a time. On a solid background a defect is obvious: a black dot on white, a glowing dot on black or a coloured dot that doesn’t change with the background.

Wipe the screen first so dust isn’t mistaken for a pixel, and look from 30–50 cm. Click, Space or an arrow key — next colour; Esc or the × button — exit. On iPhone the colour fills the screen without true full screen — that’s a Safari limitation.

Press “Start test” to fill the screen with colour.

Everything runs in your browser: sound, video and keystrokes are never sent or stored.

What next

How to read the result

  • Dead pixel — a black dot visible on white and coloured backgrounds.
  • Hot pixel — glows white on a black background.
  • Stuck sub-pixel — a red, green or blue dot on every background. It sometimes recovers on its own or after flashing colours over it.
  • A new monitor with defects can usually be returned within the store’s return window or under warranty if the defect count exceeds the brand’s pixel policy.

More tests

Frequently asked questions

How many dead pixels are acceptable?
It depends on the panel class and the brand’s policy: some replace a monitor for a single bright pixel, others allow 2–5. Check your warranty terms.
Can a dead pixel be fixed?
A dead one can’t. A stuck one sometimes recovers with rapidly changing colours over the area or gentle pressure through a soft cloth. Never press hard.
Does the test work on a phone?
Yes. Android switches to full screen; iPhone fills the screen without it. Turn brightness up.
It’s a patch, not a dot — what is it?
Patches and lines are backlight bleed or panel damage, not pixels. They show best on black and grey.