Blank Screen
One click to a clean full-screen colour — black for cleaning, white as a light panel, warm to cool presets and a dimmer. Everything runs locally in your browser.
Full brightness — the colour is shown at its own sRGB value.
Nothing here uses your camera, microphone or screen capture, and nothing is uploaded — your last colour and brightness are kept in this browser only. Press Esc at any time to come back.
How to use it
- Pick a field, then go full screen. The two shortcut buttons jump straight to black or white; the swatches, the colour picker and the dimmer all update the preview strip first so you know exactly what you are about to get.
- Change colour without leaving. Click anywhere on the field, or press ← / →, to step through the swatches. ↑ and ↓ move the dimmer in 5% steps.
- Getting out. Esc always works, and so does the Exit button in the pill. The pill fades after a few seconds so it is not in your way — move the mouse, tap the screen or press a key and it comes straight back.
- The pointer hides after two seconds of stillness so there is no arrow sitting on the field while you clean or trace. Any movement brings it back.
- Cleaning: use black, and turn the monitor’s own brightness up before you start — smears only show when the panel is throwing light through them.
- Bias light or video call: use soft light or one of the white presets, then pull the dimmer down until it stops being uncomfortable. Your choice is remembered for next time.
What the black field and the white field each show you
Black is the cleaning field. On a normal page, dust, fingerprints and dried spray marks disappear into the image; on black with the backlight up, every one of them lights up as the panel pushes light through the smear. Work in slow straight passes with a dry microfibre cloth rather than circles, and if you need moisture, put distilled water on a corner of the cloth — never on the panel, where it runs down behind the bezel. Alcohol, ammonia and household glass cleaner attack the matte anti-glare layer on most modern monitors and leave permanent cloudy patches; paper towel and tissue contain wood fibre that is harder than the coating and will scratch it.
A useful trick while you are there: move your head side to side and watch the speck. If it shifts relative to the pixels around it, it is sitting on the outer surface and will wipe off. If it stays locked to the pixels, it is behind the glass — dust that got inside during assembly, or a dead subpixel — and no amount of wiping will touch it.
Black in a dark room is also the backlight-bleed test. Bright clouds or streaks leaking in from the edges and corners are bleed: a real manufacturing fault, and it stays put as you move your head. A silvery or purple wash that only appears when you look at the panel off-axis, and changes as you shift position, is IPS glow — a property of the technology, not a defect, and it cannot be fixed. Stuck subpixels show up here too, as single coloured dots on the black.
White is the light panel and the uniformity check. As a light it is genuinely useful: tracing on paper against a laptop screen, hunting a dropped screw under a desk, or throwing fill on your face for a call. As a test it shows tint bands, warm or green corners, and blotchy patches. Note that backlight bleed is a black-field test, not a white one — on white the backlight swamps it. Dirty-screen effect, the faint mottling you notice when the camera pans in a game, is easiest to see if you pull the dimmer down two or three steps and turn the white into a light grey.
Soft light is for cameras and long sessions. A flat white rectangle is a hard light source: sharp-edged shadows on your face and an obvious bright rectangle reflected in glasses. The soft field falls off toward the edges, which reads much more like a diffused softbox — rounder catchlight, gentler shadow edges — and it is far less tiring to sit in front of than a wall of maximum white.
What this page cannot do
- It cannot change your backlight. The dimmer draws a semi-transparent black layer over the colour, which is the only lever a web page has. Less light comes out, but the backlight still draws full power and the black level does not improve. Your monitor’s own brightness button is the real control.
- The slider is not linear in light. It scales the colour’s sRGB value, and displays are gamma-encoded, so 60% on the slider emits roughly 33% of the light and 30% emits about 7%. The figure under the slider is an estimate assuming a standard gamma-2.2 display, not a measurement.
- The colour temperatures are approximations. They are blackbody colours converted to sRGB and scaled so the brightest channel sits at full. Because 6500 K is the sRGB white point, the cool preset lands on #fffefa — all but identical to plain white, which is the honest answer rather than a bluer colour that would look more convincing. Making a colour warmer costs light: 2700 K puts out around half the luminance of full white on the same panel, and 4000 K about two thirds, because two of the three channels are turned down to make it.
- It is not a calibrated light source. Fine for a bias light, a fill light or tracing; not fine for setting camera white balance, judging print colour or anything clinical.
- HDR displays will not hit peak brightness here. A browser page is composited at the SDR reference white level, so an HDR panel that can flash 1,000 nits in a film will show this field at its far dimmer desktop white.
- The wake lock is a request, not a guarantee. Some browsers have no Screen Wake Lock API and some phones drop it on low battery, which is why the panel reports what actually happened instead of claiming success.
FAQ
How do I make my whole screen a single colour?
Pick a colour on this page and press Go full screen. The browser hands the page the whole display, so you get one flat field with no toolbars, and the pointer hides itself after two seconds of stillness. Click or press the arrow keys to change colour while you are in there, and press Esc to come back. If your browser refuses full screen the tool falls back to covering the entire page instead.
What is the safest way to clean a monitor?
Switch to the black field, turn the monitor’s own brightness up so the light rakes across the surface, and use a dry microfibre cloth in slow straight passes. For a stubborn mark, dampen one corner of the cloth with distilled water — never spray the panel, because liquid runs down into the bezel. Keep alcohol, ammonia and household glass cleaner away from matte anti-glare coatings, and never reach for paper towel or tissue: the wood fibre in them is hard enough to leave fine scratches.
Does the brightness slider really dim my screen?
Not the way the monitor’s own control does. A web page cannot touch the backlight, so the slider lays a semi-transparent black layer over the colour. Less light leaves the panel, which is what you want for a bias light at night, but the backlight still runs at full power and the black level does not improve. Use the monitor’s brightness button or your laptop’s brightness key for a real change.
Why will it not go full screen on my iPhone?
Safari on iOS does not implement the Fullscreen API for ordinary page elements, so no website can take over an iPhone screen. The tool detects that and covers the whole page instead, which leaves Safari’s address bar and the home indicator visible. Adding the page to your home screen and launching it from there gets you closer to a clean field.
Will my screen still go to sleep while this is open?
Usually not. The tool asks for a screen wake lock while the blank field is showing, releases it the moment you exit, and asks again if you switch away and come back. Not every browser grants one and some phones drop it on low battery, so the panel reports whether the lock was actually held rather than assuming it worked.
Are the warm, neutral and cool white presets accurate?
They are approximations and the page labels them that way. Each one is the blackbody colour for that temperature converted to sRGB and scaled so the brightest channel sits at full, which reproduces the look of a 2700 K bulb or 4000 K office light on a roughly calibrated display. Note that 6500 K is the sRGB white point, so the cool preset comes out almost identical to plain white. None of them is a calibrated light source, so do not use one to set white balance for a camera.