ScreenHalo

ScreenHalo

A small, free and open source menu bar app that lights the wall behind your Mac display with the colors on your screen.

Local lighting for compatible USB strips using the Skydimo serial protocol.

Download for Intel Mac View source

Requires macOS 14 Sonoma or later. Intel download · No developer tools needed to run the app · MIT License

On an Intel Mac, you can also build it yourself with Xcode or Apple’s Command Line Tools. Apple silicon (M-series) version coming soon.

The real ScreenHalo menu bar popover: lights on in Screen sync mode with a live preview of the LED strip, and Brightness and Smoothing sliders.
How it works

Your screen's edges, painted on the wall.

Like an ambient-light TV, but for the monitor on your desk, using a USB LED strip on the back of your screen.

1

Sample the edges

ScreenHalo captures a small image of your selected display and samples bands along its left, top, and right edges. The bottom edge is not used.

2

Map to LEDs

Each LED follows the average color of its matching edge region. Adjustable smoothing softens transitions.

3

Send to the strip

Colors go straight to the strip over USB, and the wall glows to match.

Screenshots

Small, quiet, out of your way.

ScreenHalo Setup: choose your display, connect your USB strip, choose Screen sync or Solid color, then turn on the lights.
Setup walks you through it: pick your display, plug in the strip, turn on the lights.
The ScreenHalo menu bar popover with the lights on in Screen sync mode, a live LED preview, and Brightness and Smoothing sliders.
Everything you need, one click from the menu bar.
LED layout settings: 13 LEDs left, 26 top, 13 right, strip starting bottom left, clockwise.
Map your strip once and every LED picks up the right edge.
General settings: open at login, auto off when the display sleeps or the Mac locks, and capture settings.
General
Device settings showing an LED strip connected over USB with 52 LEDs.
Device
Shortcuts settings with global keyboard shortcuts for lights, mode, brightness and color.
Shortcuts
What you need

Your Mac. A compatible USB strip.

Choose a compatible controller and match the LED layout to your monitor.

  • An Intel Mac running macOS 14 Sonoma or later. Download the ready-to-run app or build it yourself from source with Xcode or Apple’s Command Line Tools. A native Apple silicon (M-series) version is coming soon.
  • A compatible Skydimo USB LED strip mounted on the back of your monitor. ScreenHalo uses the Skydimo serial protocol at 115200 baud, with RGB color order and up to 255 LEDs. Using the Skydimo app does not guarantee compatibility with every controller.
  • A free USB port for the strip.
Ideas for the future
  • More than screens. Desk light bars and other lighting could be explored. The current app supports one USB strip behind one selected display.
  • Windows and Linux. ScreenHalo currently supports macOS only. Windows and Linux versions are possible future projects, with no release dates.
  • Custom hardware for DIY strips. A controller for DIY strips is another possible direction. No custom hardware is available with the current app.
Get started

Up and glowing in five steps.

  1. Download and install

    Download the app ZIP from Releases, unzip it and drag ScreenHalo into your Applications folder. Choose the ScreenHalo.zip attachment, not GitHub’s source-code ZIP. No developer tools are required.

  2. Open it the first time

    Open ScreenHalo from Applications. Version 0.1.1 is signed with a Developer ID certificate and notarized by Apple. If macOS asks whether you want to open an app downloaded from the internet, click Open.

  3. Run Setup

    On first launch, ScreenHalo opens Setup. Choose the display with the strip behind it, plug your LED strip into a USB port and pick it from the list. Quit the Skydimo app first so it isn't holding the strip.

  4. Allow screen access (Screen sync only)

    Screen sync needs permission to see your screen; Solid color works without it. Click Allow screen access in Setup. If macOS asks, switch ScreenHalo on in System Settings › Privacy & Security (Apple lists it under “Screen & System Audio Recording”), then return to the app and click Check access. Quit and reopen ScreenHalo if macOS asks, or if access still appears unavailable. macOS shows a capture indicator while Screen sync is running. Screen images are processed in memory, never saved or sent over the network. Audio isn't captured.

  5. Turn on the lights

    Pick Screen sync or Solid color and click Turn on lights. If the glow looks shifted or mirrored, open LED layout and set how many LEDs are on each side and where the strip starts.

Using it

Lives in your menu bar.

Click the halo icon to turn the lights on or off, switch between Screen sync and Solid color, and adjust brightness and smoothing. The icon changes to show whether the lights are on or off. Closing the settings window keeps the app running; choose Quit ScreenHalo to exit.

On Off
Default shortcuts
ActionKeys
Turn lights on / off⌃⌥H
Switch mode⌃⌥M
Brightness up / down⌃⌥↑ / ↓
Next solid color⌃⌥C

Change them any time in Settings › Shortcuts.

Privacy

Screen colors stay local.

ScreenHalo processes frames from your selected display in memory and uses the edge colors to drive your lights. Screen images are never saved or uploaded. Your preferences are saved locally.

Why ScreenHalo exists

I wanted my desk lights to work locally, without an account or a cloud service, so I built ScreenHalo.

  • No saved screen images. Screen images are processed in memory, never saved or sent over the network. Audio isn't captured.
  • No screen data goes over the internet. Colors go straight to your LED strip over USB.
  • No account, tracking, or analytics in the app. Just install and go.
  • Open source. See how the app works: read the code.

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FAQ

Troubleshooting

Quick fixes for the most common hiccups. Still stuck? Open an issue.

The strip stays dark or only shows black.
Check that your strip has power, the correct USB port is selected, brightness is above zero, and other strip-control apps are closed. Try Solid color first: it needs no screen permission. If Solid color works but Screen sync does not, open Setup and check screen access and the selected display. Enable access in System Settings if needed, return and click Check access. Quit and reopen if macOS asks. Protected video may appear black.
The glow is on the wrong side or mirrored.
Check Settings › LED layout: check the counts for the left, top, and right sides, then choose Bottom left · clockwise or Bottom right · counter-clockwise to match your cable. The bottom edge is not sampled.
My Mac feels slow while syncing.
Turn off the lights, open Settings → General → Screen capture, and lower Update rate and Edge depth. Try 30 fps and 5–10% depth, then turn the lights back on. A lower update rate captures less often. A smaller edge depth samples fewer pixels and makes the lights follow colors closer to the screen edges.
The glow flickers.
Raise Smoothing in the menu bar popover. Higher smoothing makes color changes calmer.
Does it work alongside the official Skydimo app?
Quit the Skydimo app before using ScreenHalo. Only one app should control the strip at a time. Another app holding the port can prevent ScreenHalo from connecting.
Does ScreenHalo record or upload my screen?
No. Screen images are processed in memory, never saved or sent over the network, and audio isn't captured. ScreenHalo only uses the edge colors to drive your LED strip, and it doesn't connect to the internet. See Privacy.