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FnLamp

A native macOS app that lets you check and toggle the fn key mode right from the menu bar

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Motivation

Changing the fn key behavior in macOS requires navigating through System Settings → Keyboard → Keyboard Shortcuts → Function Keys — multiple steps every time. And there's no way to tell which mode is currently active without actually pressing a key.

FnLamp solves both of these annoyances.

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Features

Feature	Description
Menu bar indicator	Two-row LED (fn / 🌞) shows the current mode at a glance
Click to toggle	Left-click the menu bar icon to switch modes instantly
Global shortcut	Toggle from anywhere with the default shortcut ⌃⌥⌘F
Customizable shortcut	Right-click → Shortcut Settings to assign any key combination
Transition popover	A brief notification appears below the menu bar for 1 second on every mode change
External change detection	Automatically syncs the indicator if the mode is changed via System Settings or any other path

Reading the menu bar indicator

fn  🟢   ← Standard Function Keys mode (F1, F2, F3 …)
🌞  ⚫

fn  ⚫   ← Special Function Keys mode (brightness, volume, media controls …)
🌞  🟠

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Installation

Note: No pre-built binary is provided. Please build the project yourself using the macOS and Xcode versions appropriate for your system.

Requirements

• macOS 26 or later
• Xcode 26 or later

Build from source

git clone https://github.com/your-username/FnLamp.git
cd FnLamp
open FnLamp.xcodeproj

In Xcode, choose Product → Run (⌘R) to run, or Product → Archive to build a release binary.

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Usage

1. Launch the app — a small indicator appears in the menu bar (no Dock icon).
2. Left-click → toggle fn mode immediately
3. Right-click (or ⌃+left-click) → context menu
   • Toggle fn (T) — switch mode
   • Refresh State (R) — sync with any externally applied changes
   • Shortcut Settings… — reassign the global shortcut
   • Quit (Q)
4. Global shortcut ⌃⌥⌘F — toggles the mode regardless of which app has focus

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Tech Stack

• Language: Swift 5
• UI: SwiftUI + AppKit (menu-bar-only accessory app, no Dock icon)
• Global hotkey: Carbon Event Manager (RegisterEventHotKey)
• Applying settings: CFPreferences + the activateSettings utility for immediate effect without a restart

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License

MIT © 2026 Kyle Ahn — see LICENSE for details