Sigil

A macOS app that assigns custom icons to external volumes — and remembers them across unmounts, reformats, and remounts.

Screenshots

Main window — sidebar lists mounted and remembered volumes, detail pane holds the drop zone and actions

Permission prompt — on macOS 13+, the first apply asks for Removable Volumes access; click Allow

Applied state — current icon fills the canvas, ready to reset or replace

Finder — custom icons persist on the volume, visible anywhere macOS shows drive icons

Remembered group — unmounted drives keep their assignment for silent re-apply on remount

Features

• Apply custom icons from PNG, JPEG, HEIC, or .icns files via drag-and-drop or click-to-browse
• Remember every assignment in a local database keyed by volume UUID
• Silent re-apply — plug a known drive back in and Sigil writes its icon back within 1–3 seconds, no clicks required
• Conflict detection — if the volume's icon changed outside Sigil, Sigil asks rather than clobbering
• Per-volume notes — tag what each drive is for; notes show in the Remembered group even when unplugged
• Reset — one click returns a volume to its default Finder icon
• Forget — one click removes Sigil's record of a volume entirely

Why Sigil exists

macOS Finder stores a custom volume icon as a hidden .VolumeIcon.icns file on the volume itself. Reformat the drive and the icon's gone. Use it on another Mac and the icon's gone. Plug in a new drive and you get the generic silver icon forever. Sigil fixes all three by keeping the (UUID → icon) mapping locally and re-applying on remount.

Installation

1. Download Sigil-1.0.1.dmg from Releases
2. Open the DMG and drag Sigil to Applications
3. Launch from Applications folder

The DMG is notarized by Apple — no Gatekeeper warning on first launch.

Usage

1. Plug in an external volume
2. Select it in the Mounted sidebar
3. Drop or click an image onto the canvas
4. Apply — the Finder icon updates within a second

Once applied, the assignment is remembered. Eject and replug the drive anytime — Sigil re-applies silently.

Keyboard Shortcuts

Shortcut	Action
⌘S	Apply
⌘W	Close window
⌘Q	Quit

How it works

Every apply is a direct three-step write to the volume root:

1. Write the rendered .icns to /Volumes/<Drive>/.VolumeIcon.icns atomically
2. Set byte 8 of com.apple.FinderInfo to 0x04 (the kHasCustomIcon flag) via setxattr(2)
3. Bump the volume's mtime with utimes so Finder refreshes its icon cache

This bypasses NSWorkspace.setIcon(_:forFile:options:), which silently fails on volume roots since macOS 13.1. The .icns itself is generated by iconutil -c icns from a 10-file .iconset rendered at 16/32/128/256/512pt @1x and @2x.

Data

Sigil stores:

• ~/Library/Application Support/Sigil/volumes.json — UUID, name, note, hash, timestamps, plus a rolling .bak
• ~/Library/Application Support/Sigil/icons/{uuid}.icns — cached rendered icon for silent re-apply
• ~/Library/Application Support/Sigil/icons/{uuid}.src.{ext} — cached source so the icon can be re-rendered without re-picking the file

Sigil does not run in the background. The mount watcher only operates while the app is open. If a drive is plugged in while Sigil is closed, its icon re-applies next time you open Sigil.

Requirements

• macOS 14.0 (Sonoma) or later
• External volumes (USB, Thunderbolt, SD, or mounted disk image)

Building from Source

Requires Xcode 16+ and macOS 14.0+.

git clone https://github.com/Xpycode/Sigil.git
cd Sigil/01_Project
xcodebuild -scheme Sigil -configuration Release

Non-goals (v1.0)

• SF Symbol / emoji icons
• iCloud sync
• Sparkle auto-update
• Mac App Store distribution
• Background process / launch at login

Reporting bugs

Open an issue with the output of:

log show --predicate 'subsystem == "com.lucesumbrarum.sigil"' --last 1h

License

MIT