Red light preserves dark adaptation; white/blue destroys it within seconds.
Astronomy use
Use to check star charts without affecting eye dark adaptation.
Cost
100% free. No login, no ads.
Exiting
ESC key, Exit button, or F11.
Mobile
Fully works on iOS and Android.
Privacy
All in-browser. Nothing uploaded.
Common questions
FAQ
A red screen is used for: night vision preservation (red light doesn't constrict pupils), astronomy (check star charts without losing dark adaptation), darkroom photography, red chroma-key video backgrounds, and red-channel pixel testing.
The eye's rod cells — responsible for night vision — are insensitive to red wavelengths. Using a red screen to check apps or charts means your eyes stay dark-adapted so you can continue seeing faint stars. White or blue light destroys dark adaptation within seconds.
Yes. Red wavelengths (~620–750nm) have minimal effect on rhodopsin, the pigment responsible for night vision. A red screen is the safest screen colour to use in a dark environment.
Yes. While green and blue are more common for chroma-key, red can be used when the subject's clothing or skin tones don't include much red. Use our Green Screen for the standard chroma-key colour.
Press ESC, click the Exit button, or press F11.
Red Screen Online: Night Vision & Astronomy Guide
Why red light is special for vision
Human night vision relies on rod cells in the retina, which contain a photosensitive pigment called rhodopsin. This pigment is regenerated in darkness — a process called dark adaptation that takes 20–30 minutes. Exposure to white or blue light destroys this adaptation within seconds. Red light (wavelengths of ~620–750nm) is the exception: rod cells are minimally sensitive to red, so a red screen allows you to see your device screen without losing your dark-adapted vision.
Astronomy and stargazing
Astronomers have used red torches and red-filtered displays for decades. Using a red screen for your stargazing app, star charts, or notes means you can glance at your device and immediately return to observing faint nebulae, galaxies, or planets without your eyes needing to readjust.
Darkroom photography
Traditional darkroom safe-lights use red or amber light for a similar reason — most black-and-white photographic papers are insensitive to these wavelengths. While a screen is not a substitute for a professional darkroom light, a red screen can serve as a reference in controlled conditions.
Red vs other color screens
Compared to our Blue Screen (which actually disrupts sleep and night vision the most), red is at the opposite extreme. For daytime chroma-key work, Green Screen remains the industry standard. For OLED power saving, a Black Screen is most effective.