Red Screen

A full red screen lights only the red sub-pixels, so it is a quick way to test the red channel and spot dead or stuck sub-pixels. It also makes screen tint and uniformity problems easy to see, because a single flat colour exposes patchiness and brightness drift that a busy desktop hides. Dimmed right down, a red screen works as a bias light behind a monitor that is gentle on the eyes in the dark. Red light also preserves dark-adapted vision, which is why it is used for astronomy and late-night reading.

To make your whole screen red, open this red screen tool and press the Go Full-Screen Red button, or tap the red swatch. The page fills your entire display with solid red and hides the browser interface. Once you are full-screen, the left and right arrow keys switch between red, green, blue, white, black and gray. Press Esc to exit.

On a pure red field every working pixel shows only its red sub-pixel. A dead sub-pixel appears as a small dark dot and a stuck sub-pixel shows as an off-colour speck, so faults stand out against the flat background. Red alone tests only one third of each pixel, so cycle red, green and blue to check every sub-pixel. The dead pixel test runs that sequence for you.

The red screen switches to any of the other solid colors. Pick a swatch before you start, or once full-screen use the left and right arrow keys or the on-screen swatches to move between red, green, blue, white, black and gray. The white screen exposes dust and dead pixels while the black screen exposes bright and stuck ones, so run all three on a panel you are checking. For a full palette with a custom hex value, open the color screen tool.

The red screen tool uploads nothing and needs no install. It runs entirely in your browser, with no account, no download and no data leaving your device. Once the page has loaded it keeps working offline, so it still works on a machine with no connection. Closing the tab removes it completely.