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Device test

Black — shows stuck pixels and backlight bleed

In fullscreen, tap or press a key for the next colour. Press and hold on a bad pixel to mark it (or right-click, or press M). Escape leaves.

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Laptop screen test: dead pixels and pressure marks

Laptop panels add two faults monitors rarely show: pressure marks from the keyboard, and bleed along the bottom edge. Both appear on the fields below.

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The short answer

To test a laptop screen, go fullscreen and cycle through red, green, blue, white and black at maximum brightness. Dead pixels stay black on every colour and stuck pixels stay lit on one. Pressure marks are different: they show as faint light or dark patches on a solid grey or white field.

Reading what you see

Dead, hot or stuck: what each one means

What the fault looks like, whether it can recover, and how it counts towards a return.

FaultWhat you seeDoes it recover?For a return
Dead pixelA black dot on every colour, clearest on whiteNoCounts as an always-dark fault. Class II panels may have 2 per million pixels
Hot pixelA white dot on every colour, clearest on blackRarelyCounts as an always-lit fault. Class II allows 2 per million, and some makers replace a panel for one
Stuck pixelA red, green or blue dot that vanishes on a field of its own colourSometimes, with rapid colour flashingA sub-pixel fault. Class II allows 5 per million pixels
Backlight bleedLight leaking in from an edge or corner on black, in a dark room. It stays put when you move your headNoNot a pixel fault, so there is no count. It is judged by eye: photograph it in a dark room
Dust or a markA soft-edged speck that seems to shift against the picture as you move your headWipe it offNot a fault. Clean the screen before you mark anything

The class figures come from ISO 13406-2, since carried into ISO 9241-307. Most consumer screens are sold as Class II, which works out at 4 always-lit, 4 always-dark and 10 sub-pixel faults at 1920 × 1080 (Full HD), 7 always-lit, 7 always-dark and 18 sub-pixel faults at 2560 × 1440 (QHD) and 16 always-lit, 16 always-dark and 41 sub-pixel faults at 3840 × 2160 (4K). A maker's own warranty can be stricter or looser, so read it for your model.

Getting it right

Four things worth knowing

  • Look for pressure marks on grey, not black

    A keyboard pressing against the panel inside a bag leaves faint blotches that a mid-grey field reveals and a black field hides. Check for them in a line matching the key rows.

  • Bottom-edge bleed is common and often acceptable

    The backlight enters most laptop panels from the bottom, so a slight glow along that edge is normal. An obvious bright patch is not.

  • Open the lid fully and look straight on

    Laptop panels, especially TN ones, shift colour sharply with angle. A half-open lid will show you faults that are not actually there.

  • Find it before the return window closes

    A laptop screen is rarely user-serviceable, so a panel fault means a whole-machine return or a service visit. The day it arrives is the cheapest possible time to discover one.

Nothing leaves your device

This test runs entirely in your browser. There is no upload, no recording and no server that could receive anything — close the tab and it is gone.

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FAQ

Questions people ask

Anything we've missed?

Tell us

What are the faint blotches on my laptop screen?

Usually pressure marks, where the keyboard or something in a bag pressed against the panel. They show best on a grey or white field. Light ones sometimes fade; deep ones do not.

Can a laptop screen be replaced for a dead pixel?

Under warranty, if the fault meets the manufacturer's threshold. Out of warranty, panel replacement is possible on many models but not on those with a bonded display assembly.

Is backlight bleed on a laptop a fault?

Some is expected, particularly along the bottom edge. It becomes a fault when it is visible during normal use on dark content, rather than only when you go looking in a dark room.

Should I test a refurbished laptop?

Yes, immediately. Refurbished units are the most likely to arrive with a cosmetic screen fault, and their return windows are usually shorter.

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