Fill your whole display with one flat color, a gradient, or a gentle moving wash. It is the fastest way to find what a picture hides: white shows dirt on the glass, black shows stuck pixels and backlight bleed, gray shows uneven patches, and red, green and blue each isolate a subpixel the others cover for. The same flat field, turned down low, is also a genuinely good soft light for a video call.
Filling a display with a single flat color sounds trivial, and that is exactly why it is useful. It removes every variable. Whatever you can still see is either dirt on the glass, a fault in the panel underneath, or light coming from somewhere else in the room.
Cleaning. A white field turns fingerprints into dull gray clouds and makes dust obvious. Normal desktop wallpaper hides all of it. Finding faults. A dead pixel stays dark against white, while a stuck pixel is jammed on and shows against black. Single-subpixel failures only appear on the matching red, green or blue field, which is why a proper display check cycles through all five.
Light. This has quietly become the most common reason people reach for a tool like this. A phone, tablet or laptop filled with white is a genuinely good soft light source, because the panel is large relative to your face. That is what makes the light soft and the shadows gentle, and it is what photographers pay real money for.Mood. At low brightness the same screen becomes ambient light: a warm glow behind a desk, a cool wash behind a television, a color that changes the feel of a room.
Getting a clean result
Two things get in the way. Interface is the first: any toolbar, cursor or notification breaks the field, which is what fullscreen mode is for. Your display's own color management is the second. Night-shift modes and blue-light filters tint everything toward orange, and adaptive brightness can change the level under you mid-task. Turn both off before you judge a panel.
Nothing you pick here is sent anywhere. The tool runs entirely in your browser, and the color you choose lives in the address bar, so sharing the exact screen is just sharing the link.
Common questions
How do I fill my screen with a color?
Pick a swatch or dial in a hex, then press Fill screen or the F key and the color covers your whole display with no interface on it. Press Escape to come back. Nothing is installed and nothing is sent to a server.
How do I test for dead pixels?
Show white, black, red, green and blue in turn and look closely at each. A dead pixel stays dark on every color. A stuck pixel shows one color permanently and is easiest to spot against black. Checking a single color is not enough, because a healthy-looking pixel can have one failed subpixel.
Can I use my screen as a light?
Yes, and it is one of the most popular reasons people use a tool like this. A phone, tablet or laptop filled with white or warm white makes a soft, even fill light for video calls and photography. While a color is filling the screen, the browser is asked to keep the display awake.
What are the gradient and ambiance modes for?
A gradient fills the screen with two or three colors blended across it, which is what you want behind a desk or a television rather than a flat field. Ambiance moves it: breathe swings the brightness slowly, cycle laps the hue wheel, and wash turns a gradient through a full rotation. The periods run long on purpose, because the calmest failure of a room light is being noticed.
Does this work on a phone?
Yes. The tool is built mobile first, the swatches are large enough to hit accurately, and a phone filled with a color is exactly what you want for the fill-light and bias-lighting uses.