Mac function key emulation

Hi. This is a Mac keyboard question.

On the Mac, the funcition key can act as a modifier. For example a common key equivalent for “view fullscreen” is fn-F. Does anyone know if there’s there a good way to emulate the Mac function key? I’ve looked all over the UHK Agent for one, but haven’t been able to spot it.


Hi there,

Unfortunately, I can’t provide a better answer than this knowledgebase article: How can I map the Fn key of my laptop to the UHK? - Ultimate Hacking Keyboard

Hmm. IDK, there are USB keyboards with the function (Fn) key, including third-party ones, so some kind of USB HID code must exist.

Unfortunately the key mapping on the Mac doesn’t go that far. You can remap CTRL to Fn if you’d like, but then you lose CTRL, and there is no built-in way to map the left and right keys differently AFAICT. Using a software add-on somewhat feels like cheating…

Whatever gets the job done IMO. And sometimes it is better or more versatile to use a software solution instead of the magic keyboard.

Do the mentioned third-party keyboards with Fn keys emulate the native Fn keys of the Mac as expected?

IDK if the 3P keyboards do the full Apple keyboard emulation, because I do not have one, but they do have the screen brightness and volume control icons on the number row, so I’d assume so. There are a bunch of Amazon.

The codes are not listed here UIKeyboardHIDUsage | Apple Developer Documentation, but there is some discussion in various forums such as this one keyboard - What is the hex ID for Fn key - Ask Different, but it seems some degree of vendor ID fakery may be required.

The mentioned media functions are available in Agent and can be mapped to your UHK’s Fn layer.

I’ve created a firmware issue for emulating the Mac Fn key with the UHK.


Just like everything in life, it’s about tradeoffs. I still use Karabiner-Elements for a few things that I can certainly do, and probably better, with uhk macros, because if I’m using my mbp’s keyboard, I still want to access the same functionality, or at least as close as I can. It’s all about muscle memory.

Additional software, especially low-level / driver type packages aren’t always an option. I can install whatever sketcyware on my personal computer, but not on my work machines.