Red Screen
Pure red — RGB 255, 0, 0 — lights only the red sub-pixel of every pixel on the panel. That makes it both a genuinely useful low-light colour and a precise way to inspect one third of your display at a time.
What people use the red screen for
Preserve night vision
Human rod cells are least sensitive to long-wavelength red light, so a red screen lets you read a star chart, find a lens cap or check a setting without resetting the 20–30 minutes of dark adaptation you just spent earning. Standard practice for astronomy, night navigation and observatory work.
Improvised darkroom safelight
Traditional black-and-white printing papers are effectively blind to red light. A phone or tablet held on a red screen, dimmed well down and kept at a distance, works as an emergency safelight when handling those papers.
Test the red sub-pixel
If a pixel is dead in red it will read as black against this screen while looking fine on white. Cycling red, green and blue full screen is the fastest way to find which sub-pixel has failed.
Red key light for photo and video
A second monitor or tablet showing red is a zero-cost gel. Position it off to one side for a hard red rim on a portrait, or bounce it off a wall for a wash.
How to use the red screen
- 1Open the red screen — it fills the page immediately, no button needed.
- 2Press F or use the fullscreen button to go edge to edge with no browser chrome.
- 3Use the brightness slider to dial the output up as a light source or down for a dark room.
- 4Move the mouse or tap once to bring the controls back; they fade out on their own after a few seconds.
- 5Press a number key or use the colour strip to jump straight to another colour.
Frequently asked questions
Is a red screen actually better for night vision?+
Yes, with a caveat: the benefit comes mostly from being dim, and only secondarily from being red. A dim red screen preserves dark adaptation far better than a dim white one, but a red screen at full brightness will still dazzle you. Turn the brightness right down as well.
Can I use a phone red screen as a darkroom safelight?+
For most graded and variable-contrast black-and-white papers, yes — keep it dim, keep it at arm's length, and test with a scrap sheet first. Never for colour paper or any panchromatic material, which are sensitive across the whole spectrum.
How do I make the red screen fill my whole display?+
Press F (or click the fullscreen button) to enter true browser fullscreen, which hides the tab bar, address bar and taskbar. Press Escape to leave. On mobile, tapping the screen hides the controls; add the page to your home screen for a fullscreen launch every time.
What is the exact red colour used here?+
#FF0000. You can copy it from the control bar, or open the colour picker to dial in any other value and keep it in the URL so the exact shade is bookmarkable.
Does this work on phones and tablets?+
Yes. It works in any modern browser on iOS, Android, Windows, macOS, Linux and ChromeOS. Nothing is installed and nothing needs an account.
Is it free, and are you tracking me?+
Free, with no sign-up. Every tool here runs entirely in your browser — no colour choices, screenshots or usage details are sent anywhere.