Horizon Updater for Mac

Update the firmware of your GrizzLights Horizon EUC headlight from a Mac. GrizzLights only ships a Windows updater; this app does the same job on macOS.

Download for Mac

Version 1.0.0 · macOS 13 or newer · Apple Silicon or Intel · 29 MB · all releases

Horizon Updater window: firmware 1.19.6 loaded, light identified as P2 (Inmotion P6), Update button ready

What you need

The light, off the wheel, with the cap taken off its USB-C port.
A USB-C data cable (a charge-only cable won't work), plugged straight into the Mac.
The official firmware .zip from the GrizzLights firmware page. The app contains no GrizzLights firmware.

Install

Open the downloaded .dmg and drag Horizon Updater into Applications.
Open it. The first time, macOS says it can't verify the app, because it isn't signed with a paid Apple Developer ID. Click Done.
Open System Settings → Privacy & Security, scroll down, and click Open Anyway next to "Horizon Updater". You only do this once.

Update the light

Firmware: drop the GrizzLights .zip on the window, or click Choose…
Light: plug it in and click Identify Light. The light restarts and reports its model (for example P2, Inmotion P6) and its current version. Nothing is written.
Update: leave Back up first on (about 6 minutes), click Update, and keep the light plugged in until it says it's done. The app restarts the light and checks it reports the new version.

To undo an update, choose File → Restore Backup… and pick the backup the app saved. It puts back everything, calibration included.

How it keeps your light safe

It writes the same files, to the same places, with the same tool (Espressif's esptool) as GrizzLights' Windows installer, and adds checks:

If the light doesn't report its model, nothing is written. (The Windows installer falls back to the Legacy Leaperkim L1 firmware.)
It writes only to the light you identified, checked by chip ID before every step.
Each firmware file's built-in checksum is checked, and each must be built for its model.
It makes an optional full backup first, and restores a backup only onto the light it came from (one it has no record of needs your OK).
If an update is interrupted, the light can still be updated again over USB: the chip's flashing mode is in read-only memory.

Details in the README.