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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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Phone screen test: dead pixels and OLED burn-in

On an OLED phone the usual fault is burn-in, not a dead pixel — a faint ghost of the status bar on a grey field. The colours below reveal both.

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The short answer

To test a phone screen, open this page fullscreen at maximum brightness with auto-brightness turned off, then cycle through the colours. Dead pixels show as black dots on every colour. Burn-in shows as a faint permanent ghost of the status bar, navigation bar or keyboard, and is clearest on a solid grey 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

  • Turn auto-brightness off first

    The ambient sensor will change the level part way through and make a uniform field look uneven. Set brightness manually to maximum and leave it alone.

  • Grey shows burn-in that white hides

    A mid-grey field reveals uneven pixel wear far better than pure white. Look specifically where the status bar, navigation bar and keyboard sit.

  • Take the case off and clean the glass

    A smudge under a screen protector looks exactly like a stuck pixel. Clean the surface, and check with the protector removed if you can.

  • Buying second-hand? Check burn-in before anything else

    It is the most common real fault on a used OLED phone, it cannot be repaired, and a thirty-second grey field finds it.

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.

  • No sign-up and no account
  • Nothing recorded or stored
  • Works with an ad blocker on
  • Free, and staying free
FAQ

Questions people ask

Anything we've missed?

Tell us

What is OLED burn-in?

Uneven ageing of the pixels. Elements that stay on screen for long periods — the status bar, the keyboard — dim faster than the rest, leaving a permanent faint ghost. It is wear rather than a failure, and it cannot be reversed.

Is a green or pink tint a dead pixel problem?

No. A tint across a region is a panel uniformity issue, most often seen on AMOLED at low brightness. It is a separate fault, and worth reporting under warranty if it is pronounced.

Can I fix a stuck pixel on a phone?

Sometimes, with rapid colour cycling over the area for a few minutes. It works on stuck pixels and never on dead ones. Do not press on the screen — that risks making it worse.

Does this work on iPhone and Android?

Yes, in Safari and Chrome. Use the browser's fullscreen mode, turn off auto-brightness, and set brightness to maximum before you start.

Test it for something specific

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Photo by Helena Lopes on Unsplash
Before it matters

Find the problem now, not mid-sentence

Every one of these runs in the browser and checks one thing properly. Nothing is uploaded, nothing is recorded, and none of them need an account.

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