This red screen turns your phone, tablet, laptop or monitor into a red light with one tap. Night vision red starts at a deep, low level that you can dim further until the screen is only a glow, so you can read a star chart, set up a camera or check on a sleeping child without losing your dark adapted eyes. Pure red at full brightness gives the most red light and checks the red subpixels of a display. A sleep timer fades the light to black, and the page keeps the screen awake until then. It works in any current browser on iPhone, Android, Windows, Mac and ChromeOS.
How to use the red screen light
- Pick Night vision for dark sites and bedrooms, Pure red for the most red light or for testing, or Dark red and Crimson for a mood light.
- Turn your device's own brightness to the minimum first. A web page cannot lower the backlight, so this matters more than anything else.
- Use the brightness slider to darken the red further until you can just read what you need.
- Set a timer if you want the light to fade out by itself, for example 15 minutes for a bedtime routine.
- Tap the preview or press F. On a phone, swipe up or down to dim and sideways to change shade. Double tap or press Esc to exit.
- Hold the screen below eye level and point it at what you are reading, not at your eyes.
What the shades and readouts mean
| Shade | Hex and RGB | Best for |
|---|---|---|
| Pure red | #FF0000, 255 0 0 | The most red light, red subpixel checks, a bold backdrop |
| Night vision red | #330000, 51 0 0 | Stargazing, camping, bedrooms. Dim further with the slider |
| Dark red | #8B0000, 139 0 0 | A warm, low mood light |
| Crimson | #DC143C, 220 20 60 | A slightly pink red for photos and backdrops |
The Brightness readout shows how far the pixels are dimmed, Timer shows the time left before the 10 second fade to black, and Screen shows whether the page is holding the display awake.
Why red light protects night vision
Your eyes use cone cells for color in daylight and rod cells for seeing in the dark. Rods need 20 to 30 minutes in darkness to reach full sensitivity, and a few seconds of bright white light undoes much of that. Rods respond very weakly to deep red light, so a dim red light lets your cones read a chart while your rods stay ready for faint stars.
Two things decide how well it works:
- Brightness matters more than color. A bright red screen still ruins night vision. Use the lowest system brightness and dim the red until it is barely enough.
- OLED screens do it best. On an OLED phone the green and blue subpixels are fully off on a red screen. An LCD lets a little white backlight leak through them, so the red is less pure.
Astronomy clubs ask visitors to dim or redden screens at observing sessions for exactly this reason. For a softer, warmer light at home, the orange screen light is a good alternative.
Make your whole phone red, not just this page
iPhone and iPad: go to Settings > Accessibility > Display & Text Size > Color Filters, switch it on, pick Color Tint, and push Intensity and Hue to the right end. In the same Display & Text Size menu, Reduce White Point dims the screen below its normal minimum. Add Color Filters to the Accessibility Shortcut so a triple click of the side button turns your phone red at any time, in any app.
Android: Night Light and Eye comfort shield only warm the screen toward amber. Samsung Galaxy phones also have Color filter in Settings > Accessibility > Vision enhancements, which tints the screen with a color from a preset list, but most Android phones have no setting that turns everything deep red. Use this red screen full screen when you need a red light, and Dark theme in the rest of your apps.
Other uses for a red screen
- Camping and night walks: a phone on Night vision red lights a tent or a path without blinding others.
- Checking on a baby or a pet at night: a dim red light is less likely to wake them than white.
- Darkroom work: black and white photo paper is not sensitive to deep red, so a dim red screen can stand in for a safelight after a fog test (see the questions below). Film needs total darkness.
- Photo and video: pure red makes a strong backdrop or a red rim light for a product shot.
Check the red subpixels for faults
Pure red lights only the red subpixel of every pixel. On a full red screen:
- A black dot that stays in place means a red subpixel that does not light.
- A green, blue or white dot means a green or blue subpixel stuck on.
Run the full dead pixel test to check the other colors, and try the stuck pixel fixer on any stuck dot. A pixel that stays dark on every color is dead and rarely recovers. Use a black screen to make stuck pixels stand out most.
Your screen turned red by itself?
- iPhone: Color Filters or Color Tint is on, often from an accidental triple click. Turn it off in Settings > Accessibility > Display & Text Size > Color Filters.
- Windows: Night light at full strength turns the screen orange to red. Check Settings > System > Display > Night light.
- Monitor on a VGA or DVI cable: a loose or damaged cable can drop the green and blue signals and leave a red picture. Reseat or replace the cable.
- Red tint on the startup logo too: the problem is below the operating system, in the cable, the screen or the graphics card.
What a red screen in a browser cannot do
The page cannot lower your backlight below the system minimum, so the darkest red depends on your device. A screen is not a certified darkroom safelight, and Safari on iPhone keeps its address bar on screen. For other colors, the color screen accepts any hex code.
Red screen questions
Why do astronomers use red light?
The rod cells that give you night vision are much less sensitive to red light than to white or blue light. A dim red light lets you read a star chart or change camera settings without undoing the 20 to 30 minutes your eyes need to adapt to the dark. Keep it as dim as possible, because bright red still dazzles.
How do I make my iPhone screen red?
Open Settings > Accessibility > Display & Text Size > Color Filters, turn Color Filters on, choose Color Tint, then drag Intensity and Hue all the way to the right. Add Color Filters to Settings > Accessibility > Accessibility Shortcut and a triple click of the side button switches the red tint on and off.
Is a red screen good before sleep?
A dim red or amber light is less disruptive at night than bright white or blue light, which is why it is popular for night lights. Keep the brightness low and use the timer so the light fades out by itself. It is a gentler light, not a treatment, and it does not replace sleep advice from a doctor.
Can I use a red screen as a darkroom safelight?
Only for black and white photo paper, and only after a fog test: leave a coin on a sheet of paper under the screen for a few minutes, then develop it. If the coin's outline shows, the light is fogging the paper. Film and color paper need total darkness.
Does a red screen save battery?
On an OLED phone, yes. Only the red subpixels light up, and at the Night vision level they give only a few percent of their full light, so a dim red screen uses far less power than white. On an LCD the backlight stays on, so the saving is small.
Why is my whole screen red?
Usually a setting: Color Filters on iPhone, a strong Night light on Windows, or an accessibility shortcut pressed by accident. If the red tint also shows on the startup logo before Windows or macOS loads, check the cable, then the screen or graphics card.