VKT Toolkit · October 8, 2026 · 6 min read

Dead Pixel Test Online: Check Your Screen in About 30 Seconds

You open a new laptop, notice one faint dot near the corner, and now you cannot look away. Was it there yesterday? Is it a dead pixel, a crumb under the glass, or just something on the screen protector? And is it bad enough to send the thing back?

A dead pixel test answers that question in about half a minute. VKT Screen fills your whole display with solid colours — white, black, red, green, blue and three greys — so a single misbehaving dot has nowhere to hide. It runs in the browser: no download, no sign-up, and nothing from the test leaves your device.

What a screen test can and cannot find

First, the honest part: a slideshow of solid colours finds pixel-level faults. It will not tell you whether the backlight is failing, whether there is a hairline crack, or whether the panel is simply a cheap one. Here is what does show up:

• A lit dot on a dark background — a sub-pixel stuck fully on. Easiest to spot on black;
• A dark dot on a light background — a sub-pixel stuck off;
• A tinted dot — one of the three sub-pixels is dead, so the dot reads pink, cyan or yellow. Clearest on pure red, green and blue;
• Uneven brightness — a patch lighter or darker than its surroundings, and backlight bleed along the edges.

Note what this is not: it is not a diagnosis. It helps you see something and record it. If you are going to claim a warranty, that record is the part that matters.

How to run the test (about 30 seconds)

Open VKT Screen, pick a mode, press Start. The screen fills with one colour at a time and you tap to move on. Four details separate a test that works from one you end up repeating:

1. Lighting matters. Dim the room a little, or use normal indoor light — but keep direct sunlight off the panel, because it washes faint defects out;
2. Hold the phone about 30 cm away and look straight at it, not at an angle. Off-axis viewing hides exactly the kind of dot you are hunting;
3. Scan each colour row by row, top to bottom, the way you read. Most defects hide near the edges or around the camera hole — the places your eye skips;
4. Mark what looks wrong. Long-press the spot and it is recorded; a results page then lists every mark you made.

On a laptop with a notch, or a foldable, the cutout and the crease are where most surprises live. And wipe the panel with a soft cloth first: a surprising share of "dead pixels" turn out to be crumbs.

Quick check or full check?

Three modes, all configurable:

The eight colours are pure white, pure black, pure red, pure green, pure blue, and dark, mid and light grey. There is also a grid overlay you can switch on when you want to write down where a dot is — "third row, near the left edge" is a far more useful support ticket than "there is a dot somewhere". If six seconds per colour feels rushed, set the time per colour yourself. A quick pass is 3 colours in 18 seconds; a full pass is 8 colours in 48.

Phone, laptop or external monitor

• Phone or tablet: switch off auto-brightness and go to maximum brightness — a stuck-off pixel hides on a dim panel. Rotate the device once and repeat, since some defects are easier to catch in one orientation;
• Laptop: run on battery if you can, because some panels shift brightness slightly while charging. On a notched screen, look at both sides of the notch;
• External monitor: press F11 so the browser goes fullscreen with no toolbars, and sit at your normal distance. Then move the panel gently: a dot that flickers with the cable is a connection problem, not a dead pixel;
• TV or console display: if the browser cannot go fullscreen the test still works, you just see a thin strip of browser chrome. Use the biggest screen you can plug in.

If you do find a defect

Three steps, in order:

1. Run it twice, on a different colour and at a different brightness. A dot that shows up in every colour is real; one that appears only on white is more likely dust;
2. Record it properly. Note the colour it shows on and roughly where it sits. The results page keeps this round's marks and nothing is uploaded — if you want evidence for a return, photograph the screen with the mark visible;
3. Check your return window before you argue. Most manufacturers treat a small number of defective pixels as within specification, and the threshold varies by brand and panel class. Ask the seller for their policy in writing, and mention the defect while the return window is still open. Internationally standardised classes for pixel faults do exist (ISO 9241-307 is the one usually quoted), but the policy that actually binds you is your seller's.

And if nothing turns up, that is a result too. Run it once more a week later — a marginal sub-pixel sometimes fails completely once it has been warm for a while, and the mark you took on day one is exactly the kind of record a seller cannot argue with.

FAQ

More guides in the VKT blog.