White screen

A full screen of pure white, sent to your display as sRGB 255, 255, 255 with no tint or dimming applied.

Dim 100%

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What this test can and cannot tell you

This page sends your display an exact value (#FFFFFF, or 255, 255, 255 in RGB) and fills the screen with it. That part is reliable.

What comes out the other side is not something a browser can see. Your panel, your operating system colour profile, your brightness setting and the light in your room all change what you perceive, and nothing on this page can read any of them. Judging colour properly needs a colorimeter; judging a fault needs your eyes on a clean field, which is what this gives you.

The dim slider is the one control that changes what is sent to the panel. Leave it at 100 per cent whenever you are making a judgement about the display.

More on this: what a browser cannot detect and how these measurements work.

What a white screen is for

Finding dust, smears and scratches

Against a bright even field, anything sitting on top of the glass casts a shadow or scatters light, so specks and smudges that vanish against a normal desktop become obvious. This is the fastest way to decide whether a dark dot is a pixel fault or a piece of dust: wipe the area gently with a dry microfibre cloth and look again. Dust moves or disappears. A pixel stays exactly where it was, at exactly the same size, every time.

Spotting dark and dead pixels

A dead pixel is permanently off, so on a white field it shows as a black dot, and white is the single best field for finding one. Partial failures are subtler: if only one sub-pixel is out, the pixel still lights on white but takes on a faint colour cast, so look for a dot that is slightly cyan, magenta or yellow rather than grey. Get close enough to see individual pixels, then step back to arm length and sweep the screen slowly in bands rather than trying to take it all in at once.

Judging tint and white balance

A white field is where a colour cast becomes visible, because there is nothing else on screen to compare against. Laptop panels commonly drift warm and yellow with age, and a mismatched OS colour profile can push a screen noticeably blue or pink. The reliable way to judge it is comparison: open this page on two devices side by side, or hold a sheet of plain white paper next to the screen under daylight. Do turn off Night Shift, Night Light, f.lux and any adaptive colour feature first, because all of them warm the display deliberately.

Checking edge-to-edge brightness

Look for corners that are dimmer than the centre, a band of uneven brightness down one side, or a faint mottling across the field. Some falloff towards the edges is normal, especially on large or edge-lit panels. What is worth acting on is a sharp step in brightness, a distinctly darker corner, or a patch that looks like a thumbprint pressed into the picture.

Using the screen as a light

A white full screen makes a decent soft light at short range: fill light for a video call, a backlight for reading a film negative or tracing a drawing, or an improvised torch. A tablet held just off to one side of your face gives noticeably better results on a call than a ceiling light directly overhead.

How to run this test

Wipe the screen with a dry microfibre cloth before you start, so dust does not read as a pixel fault.
Go full screen and set your display brightness to a level you can look at comfortably.
Sweep the screen in horizontal bands at arm length, looking for black or off-colour dots.
Step back and check the corners against the centre for dimming, and the whole field for a colour cast.
Turn off Night Shift, Night Light or any warm-light feature before judging tint.

What a problem looks like

Dark dots that stay put: A dot that survives a wipe and appears in the same place every time you load the page is a pixel fault, not dirt. Note where it is before you contact the retailer.
Yellow or blue cast: A uniform tint across the whole field usually means a colour profile or a warm-light feature is active. A tint that covers only part of the screen points at the panel itself.
Vignetting and mura: Gradual darkening towards the corners is vignetting. Irregular cloudy patches are mura, a manufacturing artefact in the panel layers. Both show more clearly on grey than on white.

What to do next

If something looks wrong, check it again in a normally lit room and from straight on, then check whether it appears on a second device. If it only happens on this screen and you are still inside the return window, that is the time to contact the retailer.

Questions people actually ask

Why does my white screen look yellow?

Most often a warm-light feature is on: Night Shift on Apple devices, Night Light on Windows, or an equivalent on Android. Turn those off and look again. If it is still yellow, check your display colour profile, and compare against a second screen before assuming the panel has aged.

Is a white screen good for finding dead pixels?

It is the best single field for dead pixels, because a fully dead pixel is black and stands out sharply. It is the worst field for stuck pixels, which are lit and hide against a bright background. Run black and the three primaries as well to cover both cases.

Can I use a white screen to check for a scratch?

Yes, and it works better than a dark field for surface damage. A scratch catches the light and shows as a bright line, while a mark under the coating stays dark. Tilt the screen so light rakes across the surface to tell the two apart.