Rainbow Screen

This rainbow screen fills your phone, tablet, computer or TV with moving rainbow colors. Choose a color cycle that fades the whole screen through every hue, flowing bands that slide across the screen, or still bars from red to violet, then set the speed from a slow minute per cycle to a lively two seconds. A dimmer and a timer make it a mood light that fades out on its own, and the page keeps the screen awake while it runs. Colors always blend smoothly with no flashing. It works in any current browser on Windows, Mac, ChromeOS, Android, iPhone and iPad.

How to use the rainbow screen

1. Pick a mode: Cycle changes the whole screen through the rainbow, Flow moves rainbow bands sideways, Still bars shows seven fixed bars.
2. Set the speed. The slider runs from 60 seconds per cycle to 2 seconds, and the One cycle readout shows the current time.
3. Dim it for a room light, and pick a timer if it should fade out by itself.
4. Click the preview, tap it, or press F. Use the left and right arrow keys or swipe sideways to switch modes, up and down to change brightness, and Space to pause the colors.
5. Press Esc or double tap to exit.

The three modes

A party and mood light

A TV or a spare monitor running the rainbow screen lights a room with slowly changing color:

• Calm evening: Cycle at 30 to 60 seconds, 30% brightness, with a 60 minute timer.
• Party: Flow at 4 to 6 seconds, full brightness, on the biggest screen you have.
• Kids' room: Cycle at 20 seconds and 15% brightness as a night light, with a 15 or 30 minute timer that fades it out.

Phones and tablets work too. Stand one on a table facing a wall and the wall picks up the color.

Check colors and smooth motion

The rainbow is also a quick check of your screen and its connection:

• Still bars should show seven distinct colors. If a bar is missing or two bars look alike, one color channel is not arriving. Reseat the cable, then check with the monitor color test.
• Flowing bands should glide without stutter. Jerky or uneven movement points to a frame rate problem. The refresh rate test shows the rate your screen is running at.
• Color cycle should fade evenly. Steps or stripes in the blends show limited color depth, common on 6 bit panels and over screen casting.

Gentle on sensitive eyes

The colors change smoothly and the screen never flashes from dark to light. At the fastest setting the whole rainbow takes two seconds, which keeps the change far below the three flashes per second that web accessibility guidelines set as the limit. When your phone or computer has Reduce motion turned on, the page opens on Still bars, and Space pauses any mode instantly.

Seeing rainbows you did not ask for

• Flashes of red, green and blue on a projector: single chip DLP projectors draw colors one after another with a spinning color wheel, and some people see brief rainbow fringes around bright objects when they move their eyes. It is called the rainbow effect. Projectors with faster wheels, LED or laser light sources reduce it, and 3LCD projectors do not have it.
• Rainbow lines or bands on a TV or phone: colored lines that stay on every picture, including the device's own menus, mean a damaged panel or a loose display connector, often after a knock or a drop.
• Rainbow patterns on a monitor in photos: that is moiré between the camera sensor and the pixel grid, not a fault. Move the camera or focus slightly off the screen.

A tv test pattern makes lines, color faults and focus problems easy to see on a TV or projector.

What a rainbow screen in a browser cannot do

Screens make every color from red, green and blue light, so the deep violet at the edge of a real rainbow is out of reach and shows as a blue purple. For a steady violet or lavender, the purple screen has its own shades. The page cannot sync with music or control smart bulbs, and it cannot raise your backlight. For a single color that stays put, use the color screen, or the pink screen light for a soft pink glow.

Rainbow screen questions