Double Rainbow Screensaver_
A calm double rainbow for your screen
Eight looks
Keyboard & mouse
Guide — a double rainbow on any screen in a minute
Pick a sky, move the sun, go fullscreen. Everything runs in your browser.Choose one of eight skies: Green hills, Waterfall mist, Storm clearing, Sunset, Moonbow night, Tropical, Desert after rain or Snow-dust, or press 1 to 8. A look sets the sun, rain, mist and bow brightness in one go.
Drag the sun elevation slider or press ↑ ↓. A lower sun makes a taller bow; once the sun is above about 42° the main bow sinks below the horizon. Press L for a time-lapse that raises the sun and lets the bow grow, then fade.
Set rain, mist, drop size and bow brightness, and switch the secondary bow and the faint extra arcs on or off. Press M or click the scene in fullscreen to make it rain and watch the bow form.
Press E to label both bows, the dark band and the angles on the live scene. Turn on captions (C) for calm lines or optics facts, and ambient rain and wind (A), which is off by default and generated in your browser.
Press Enter fullscreen, click the scene or press F. Space pauses, P saves a PNG wallpaper up to 4K, and Copy link shares your exact sky. Esc leaves fullscreen.
What is in here
- Primary
- About 42° from the anti-solar point, red on the outside
- Secondary
- About 51°, fainter, colours reversed
- Dark band
- Darker sky between the bows (Alexander’s band)
- Extra arcs
- Faint pink and green fringes inside the main bow
- Sun height
- Lower sun, taller bow; none above about 42°
Rain curtains, drifting mist, soft clouds, god-rays and layered hills with haze that grows with distance. The bow only forms where there is water in the air, so more rain or mist makes it stronger, and Make it rain brings it up within seconds.
- Explain
- Labels the bows, the band and the angles live
- Forecast
- A made-up daily line with a look to try
- Clock
- Large soft time and date overlay
- Captions
- Calm lines or optics facts
Save as wallpaper renders the current scene at 1080p, 1440p or 4K. Copy link stores the look, sun, weather and switches in the web address, so the same sky opens for anyone.
The double rainbow screensaver, explained
What it is
A free, fullscreen double rainbow screensaver that runs in your browser. Instead of a looping picture, the sky is computed live: a primary and a secondary bow, the dark gap between them, faint extra arcs inside the main bow, rain curtains, drifting mist, layered hills, soft clouds, god-rays and a few birds or butterflies drawn as simple silhouettes. This page is an independent tribute to the 2010 viral video of the same name; it uses none of its footage, sound or speech and is not affiliated with it.
Use it as a screensaver, wallpaper or calm display
Press Enter fullscreen or F. In fullscreen the controls and the cursor hide after a couple of seconds, and the page asks the browser to keep the display awake where the Screen Wake Lock feature is supported. A web page cannot register itself as your operating system’s screensaver, so open it whenever you want it, or leave it on a TV, a spare monitor or a laptop on power. On iPhone the page fills the browser window, because Safari does not let a page take over the whole display. For a still wallpaper, pick a moment and press Save as wallpaper; the PNG is rendered again at 1920 × 1080, 2560 × 1440 or 3840 × 2160 (4K), limited to what your graphics card supports.
What you see in the sky
Everything below follows how real rainbows work, simplified for a calm picture.
- Primary bow: sunlight enters a raindrop, reflects once inside and leaves. Red comes out at about 42° from the anti-solar point (the point directly opposite the sun, in the shadow of your head), violet at about 40°. So red is on the outside.
- Secondary bow: light that reflects twice inside the drop comes out at about 50° (red) to 53° (violet). It is fainter, and its colours are in reverse order, with red on the inside.
- Alexander’s dark band: the sky between the two bows receives almost no light from either path, so it looks darker. It is named after Alexander of Aphrodisias, who described it around 200 AD.
- Brighter sky inside: the sky inside the primary bow is brighter than the sky outside the secondary one.
- Supernumerary bows: faint pink, purple and green arcs just inside the primary. They are an interference effect of light waves and show best when the drops are small and similar in size.
- Sun height: the bow is a circle around the anti-solar point, and the horizon cuts it off. The top of the main bow stands about 42° minus the sun’s elevation above the horizon, so a low sun gives a tall bow, and with the sun higher than about 42° the main bow lies below the horizon. The slider in this page does exactly that.
- Colour: a low sun is redder because its light crosses more air, and the bow follows. Drop size changes the width and purity of the colours; very small droplets such as in fog give a broad, almost white bow.
- Moonbow: bright moonlight makes bows too, but they are faint and look white because our eyes do not see colour well in the dark.
- Why the sun is not in the picture: you look away from the sun to see a rainbow. The scene shows what that sun does instead: long shafts that seem to fan out from the anti-solar point, and at low sun the pink glow and the blue shadow of the Earth near the horizon.
The page computes the bow from the refraction of light in water for each wavelength, blurs it with a wave-optics profile that depends on drop size, and converts the result to screen colours. It is a picture, not a measurement: it leaves out polarisation, the real size spread of drops and much else.
The eight looks
- Green hills: rolling fields, farm buildings and mist after a shower. The classic.
- Waterfall mist: a bow forming in rising spray, mirrored in the pool. Spray makes real bows too.
- Storm clearing: dark clouds breaking over a field, with shafts of light.
- Sunset: a very low sun, a huge bow and warm clouds over a lake.
- Moonbow night: a faint white bow, stars and the Milky Way over a quiet lake.
- Tropical: palms, sand and a turquoise sea.
- Desert after rain: red rock and cacti, with a sudden bow as a shower leaves.
- Snow-dust: frosted pines and diamond dust. This one is artistic: ice crystals make halos rather than rainbows, so the pastel bow inside a faint halo is imagined.
Controls, time-lapse and extras
Sliders set the sun elevation (0° to 60°), rain, mist, drop size, bow brightness and colour saturation, and two switches turn the secondary bow and the faint extra arcs on or off. Time-lapse moves the sun slowly up and down between 0° and 50°, so the bow grows, shrinks and fades; at speed 1 a full cycle takes five minutes, at speed 10 thirty seconds. Make it rain brings in a shower, and the bow forms over a few seconds. Explain this sky draws labels and the 42° and 51° circles on the live scene. Captions show a calm line or an optics fact every few seconds, and are off by default. The clock overlay shows your local time and date. The rainbow forecast is made up fresh each day from the date, is purely for fun, and has nothing to do with real weather.
Ambient rain and wind is generated in your browser with the Web Audio API, from noise, with no audio files. It is off by default and can only start after you switch it on, because browsers block sound until you interact with the page. It follows the rain slider, and a volume slider sits below it.
Performance and fallback
With a graphics card, the sky is drawn by a WebGL shader on one full-screen layer. Without one, or if WebGL fails, the page switches to a Canvas 2D painter that draws a simpler version of the same scene; add gl=0 to the link to force it. The canvas resolution follows your screen, capped at a few megapixels. If the page measures fewer than about 38 frames per second for three seconds, auto quality lowers the number of particles and then the resolution; switch it off in the Quality section or with aq=0. Everything pauses in a hidden tab. If your system asks for reduced motion, the page starts calm: clouds drift slowly, birds and the time-lapse are off and the look change does not flash.
Share a link
Copy link to this sky builds a web address with your settings. Open it and you get the same sky. You can also write the parameters yourself:
| Parameter | Values |
|---|---|
look | hills, falls, storm, sunset, moon, tropic, desert, snow (or 1 to 8) |
sun | 0 to 60 (sun elevation in degrees) |
rain mist | 0 to 100 |
drop | 2 to 30 (drop size in tenths of a millimetre) |
bright | 1 to 10 (bow brightness) |
sat | 0 to 160 (colour saturation in percent) |
tls | 1 to 10 (time-lapse speed) |
sec sup tl clock scan life spark | 1 or 0 (secondary bow, extra arcs, time-lapse, clock, scanlines, birds and butterflies, dew sparkle) |
cap | 0 off, 1 calm lines, 2 optics facts |
expl | 1 to open with the Explain overlay |
sd | 0 to 999 (landscape variation) |
fs=1, aq=0, gl=0 | open in fullscreen, switch auto quality off, force the Canvas 2D painter |
Ideas
- Calm background: Green hills or Tropical at low rain, captions off, on a spare monitor.
- Desktop wallpaper: set the sun to taste, choose 4K and save a PNG.
- Teaching: open Explain this sky, drag the sun and let the class watch the bow sink below the horizon.
- Evening: Sunset or Moonbow night with the ambient rain at low volume.
Works everywhere, privately
It runs in current browsers on Windows, Mac, Linux, Chromebook, iPhone, iPad and Android. Everything is drawn on your device and nothing about your use is sent anywhere. Your settings are kept in your browser’s local storage, and Copy link puts them into the web address in plain text. No account, no ads, no watermark.