None of the keys in my keyboard (Microsoft Sculpt Ergonomic Keyboard) are natively recognized as the Fn key by OS X (I checked with Mouseposé)

I have Karabiner and Keyboard Maestro installed but:

  1. Karabiner doesn't seem to have a template to map things to Fn
  2. As shown below, there doesn't seem to be an option in Keyboard Maestro to enter by hand Fn

How can I bind a key (specifically I am hoping to map F15) of my keyboard (e.g. F15 to Fn)?

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3 Answers 3


Try the DoubleCommand (free, sourceforge) project. According to the features page, you can map the fn key, though it's only listed as partial support. I don't have any personal experience to share...

  • Thanks for the suggestion. It looks like it comes with few pre-defined settings so it doesn't let me define a specific key to map to Fn (similar to Karabiner), but it's good to know. Sep 17, 2014 at 14:51

You can easily map to Fn keys with Karabiner by using a KeytoKey map. For example, on my Microsoft Sculpt, I wanted the F12 key to show my desktop. The default Mac command for this is F11, but I'd previously mapped F11 to something else. Luckily, Karabiner maps map to original assignments, not other customizations, so I simply used:

<autogen>--KeyToKey-- KeyCode::F12, KeyCode::F11</autogen>

So when I hit F12, it has the original Mac effect of F11, which is to show my desktop.


I had the same problem, but this seems to work on my setup. Not the same keyboard, but an original Windows keyboard without Fn-key (A Saitek).

You need to tick the box after writing new items in your private.xml. I.e. the private.xml file doesn´t activate the re-map, just makes it an option in the "Karabiner Preferences" (on top). I made this mistake at first.


    <name>F13/PrtScr to Fn</name>
    <autogen>__KeyToKey__ KeyCode::F13, KeyCode::FN</autogen>

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