I observed some questions on the Internet concerning this.

Karabiner-Elements can map from F1~F24, but can only map to F1~F20

And you can tell the OS is aware of there keys from this reply: https://forum.keyboardmaestro.com/t/f-keys-f13-to-f24/8953/7

So what's peculiar about F21~F24 on MacOS?

  • Which actual problem are you trying to solve here? Are you looking for ways to use a keyboard with F21-F24?
    – nohillside
    Aug 14, 2020 at 12:36

2 Answers 2


If this post at the Hammerspoon GitHub site is right:

enter image description here

then macOS does not handle F21~F24 (0x70~0x73) at all.

And it makes sense for Karabiner to not deliver any of these keys to the OS because of that.

  • That’s not correct. The OS receives scan codes. Whether macOS does anything with them is irrelevant. If it’s received, you can work with it. You need to see if the OS is receiving the scan code. See this answer: apple.stackexchange.com/a/317556/119271
    – Allan
    Aug 14, 2020 at 12:25

It tested it on my Macro-Pad with QMK firmware.
Assigned F21, F22, F23 and F24 to some keys.

MAC OSX (10.15.7) receives it (tested with Karabiner EventViewer) and you can assign it in Karabiner.

enter image description here

  • 1
    Karabiner can detect them, and that's what I was saying. Try with another app like Emacs. I doubt it can detect them.
    – nichijou
    Mar 31, 2021 at 16:02

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