Mapping Mac Fn Key to Application Key on External Keyboards


In the realm of customization and personalization, tailoring your devices to work seamlessly according to your preferences is crucial for a productive workflow. For Mac users who connect external keyboards, remapping keys can significantly enhance the user experience. In this blog post, we’ll delve into the process of mapping the Mac Fn key to the Application key on an external keyboard using the powerful tool, Karabiner Elements.

Step 1: Install Karabiner Elements

To get started, download and install Karabiner Elements from the official website ( This tool serves as the gateway to effortless keyboard customization.

Step 2: Open Karabiner Elements

Launch the Karabiner Elements application from your Applications folder.

Step 3: Navigate to Complex Modifications

Click on the “Complex Modifications” tab within the Karabiner Elements window.

Step 4: Add a Rule

Select the “Add Rule” button at the bottom of the window to create a new rule.

Step 5: Import a Rule

Access a library of community-contributed rules by clicking on “Import More Rules from the Internet.”

Step 6: Search for the Desired Rule

Utilize the search bar to find a rule specifically designed to remap the Mac Fn key to the Application key on an external keyboard.

Step 7: Enable the Rule

Enable the desired rule by clicking the checkbox next to its name.

Step 8: Adjust Settings (if necessary)

Customize additional settings or options that come with the rule based on your preferences.

Step 9: Reload Configuration

Apply the changes to your keyboard configuration by clicking the “Reload” button in the menu bar of Karabiner Elements.

Step 10: Test the Mapping

Connect your external keyboard to your Mac and verify whether the Fn key now functions as the Application key.


Karabiner Elements empowers Mac users to personalize their keyboard experience, unlocking new levels of productivity. By mapping the Fn key to the Application key on an external keyboard, you can streamline your workflow and make your devices work for you.