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Rory Stephenson

Karabiner Function Key Rule Generator

On macOS, F1–F12 act as media keys (brightness, volume, etc.) by default, and you hold Fn to get the actual function keys. This tool generates Karabiner-Elements rules that reverse this behavior for specific apps — so F keys act as function keys in those apps while remaining media keys everywhere else.

Select apps where F keys should act as standard function keys:

Also map Fn+F key to media key action when override is active

How to use

Copy the generated JSON, then either:

In Karabiner-Elements, go to Complex Modifications → Add your own rule, paste, and save.
Save it as a .json file in ~/.config/karabiner/assets/complex_modifications/, then enable it via Complex Modifications → Add predefined rule.