Karabiner on macOS

Karabiner-Elements is a powerful, low-level keyboard customizer for macOS. It enables global remapping, complex multi-key rules, and per-application profiles — useful for developers, power users, and anyone who wants to tailor keyboard behavior beyond System Preferences.

Why use Karabiner?

System-wide remapping - Remap keys globally (e.g., swap Caps Lock and Control)
Context-aware rules - Create rules for specific apps
Complex modifications - Combine simple modifications with tap vs hold behavior
Low-level stability - Works everywhere: login screen, terminal, all apps

Quick Setup

Download and install Karabiner-Elements
Open Karabiner Preferences and enable the app
Add rules via the "Complex Modifications" tab or edit ~/.config/karabiner/karabiner.json directly

Common Use Cases

Example 1: Windows Keyboard Profile

Create a separate profile for a Windows keyboard on macOS to maintain familiar key layouts.

Example 2: Swap Command and Control

Switch left_command and left_control keys on the Windows keyboard. By default, the Windows key maps to Command. If you're used to Cmd + C for copying, this switch makes the Ctrl key on your Windows keyboard act like the Command key. Karabiner Settings

Example 3: Caps Lock as Alfred Trigger

Map Caps Lock to Cmd + Ctrl + Opt + Shift + Space to launch Alfred instantly.

Instead of pressing the full Cmd + Ctrl + Opt + Shift + Space combination, just hit Caps Lock and Alfred appears!

Configuration:

Add this rule under the "rules" array in your karabiner.json:

{
  "manipulators": [
    {
      "description": "Change caps_lock to command+control+option+shift+spacebar.",
      "from": {
        "key_code": "caps_lock",
        "modifiers": { "optional": ["any"] }
      },
      "to": [
        {
          "key_code": "spacebar",
          "modifiers": ["left_command", "left_control", "left_option"]
        }
      ],
      "type": "basic"
    }
  ]
}

Resources

Official Documentation
Complex Modifications Gallery
Config location: ~/.config/karabiner/karabiner.json