RedLight is designed to help preserve your scotopic vision (vision under low-light conditions) by reducing the blue and green components of your monitor’s output, leaving mostly red, which aids in preserving biological night vision.

The human eye’s scotopic vision is most sensitive to light in the blue-green range and is less sensitive to red light. This is why red light is often used for night vision activities, as it does not disrupt the eye’s natural scotopic vision as much as other colors of light would.

This app overlays a red light filter on top of all other windows, allowing you to continue working through the night and preserving your night vision