The Hidden Secrets of the Fn Key

Originally published at: The Hidden Secrets of the Fn Key - TidBITS

The Fn key has been a fixture on Apple keyboards for decades, but many Mac users lack a sense of its purpose. Adam Engst thought he was going to write a quick article listing hidden keyboard shortcuts that tap the Fn key but got dragged into documenting the history and capabilities of this unsung key.

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A very handy list - thank you. Several seem to be useful for people who prefer to not use a mouse, including visually impaired.

For an ancient DOS app that I sometimes use within Boxer/DOSbox the Fn-M combination used to be equivalent to the INSERT key that is missing from Mac keyboards (it swapped between insert and replace modes). That no longer works but I did notice that the Apple symbol was highlighted and, using the left/right arrow keys, I could traverse and select the Boxer menu bar. Not very useful but there you go!

I haven’t found a key combination to change between INSERT & REPLACE but I did find a useful combination (there are numerous suggestions online). My Apple keyboard has a numeric keypad that includes a CLEAR key. I have never used (or noticed!) this key but found it swaps the numeric keypad between numbers and arrows. When in arrow mode the zero key on the numeric keypad will insert spaces in my DOS app. This is helpful for correcting minor mistypes (or should that be typos?).

Fascinating article, thanks!
The fn-delete for delete forward has been around for decades but these additional shortcuts are a revelation.

In the past, I’ve tried getting Keyboard Maestro (and before that, QuicKeys) to recognize fn to no avail. Maybe now it will.

The Fn key is getting a lot of coverage lately. For those who like to learn from videos Gary Rosenzweig of MacMost.com recently posted a very informative video tutorial about it. https://macmost.com/the-mac-fn-globe-key-everything-it-can-do.html

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Unlikely unless Apple supports it in the public Hot Key API. @peternlewis doesn’t like to delve into low-level stuff that Apple can change at a moment’s notice.

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Fn keys were quite common on PC small form-factor laptops before the PowerBook G3. My Zenith 286 SupersPORT from the early ‘90s had one, to access the numeric keypad and other keys that were mapped on top of regular keys (see this keyboard image (eBay)).

Now, a real Apple keyboard mystery is the top left key on Apple’s UK keyboard layout (Amazon). Neither the section sign, nor the combined ± symbol, are things we Brits use regularly (if at all), so why do Apple continue to include them there?

(Updating to add: I map my Caps Lock keys to Control, because I spent a lot of time previously using keyboards with it to the left of A. But it gets confusing if I have to type on colleague’s keyboards.)

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a real Apple keyboard mystery is the top left key on Apple’s [UK keyboard layout Neither the section sign , nor the combined ± symbol, are things we Brits use regularly (if at all), so why do Apple continue to include them there?

Oddly quite a few of Apple’s keyboards have that same top left key, including Arabic, Bulgarian, Dutch, International English, Greek, Hebrew, Portuguese, Romanian, Russian, and Turkish.

I haven’t found a key combination to change between INSERT & REPLACE

I think replace (overwrite) is only available in certain apps that support it, like Word and LibreOffice.

The video tutorial that @danaeugene linked to (which I “watched” in transcript) is a very nice supplement to Adam’s article.

A useful note to the list of Fn key shortcuts is that after you use Fn-A to switch keyboard focus to the Dock, you can access the submenus of Dock items by using the arrow keys (no further Fn key press required).

Interestingly, switching the Caps Lock key with the Globe key works on my 2022 MacBook Pro’s built-in keyboard, but not on the Bluetooth-connected Apple Magic Keyboard (model A1843, without Touch ID), even after a restart. Those who use Mac laptops in clamshell mode should be aware of this potential complication.

I use Fn key via Keyboard Maestro, not as a modifier key (I don’t think that’s possible?), but just as a simple trigger, in my case for brightness down. Screenshot below. I do this via the “USB device key” trigger.

Like @ace , I use “F1 through F12 to switch among my core apps” (to quote from his article). But I still like having easy access to Brightness Down / Brightness Up (which is lost when using F1 through F12 as standard function keys … and Fn-F1/Fn-F2 is not easy enough for me).

So my solution is, via Keyboard Maestro, to link Fn is down to Brightness Down, and Left Control is down (also via the USB Device Key trigger) to Brightness Up. Relatedly, I have long switched my Caps Lock key to a Control key, which anyway gives me a Control key that is easier to reach than the default one. (And it makes Caps Lock more useful than mapping it to “No Action”, as Adam has done.)

Not sure how clear my description of the above is, but my main point is that the Fn key can be put to use via Keyboard Maestro, a feature which does not seem to have been acknowledged in the above discussion. (@rowan I’ll mention you here because it seemed you were interested in this.)

Here’s my screenshot (“Apple Internal Keyboard / Trackpad #3” is just what pops up when I create a USB Device Key trigger and hit the Fn key when the first field is focused):

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Fn-Return is often Enter, which is sometimes/often(?) distinct from Return. In dialogs that accept multi-line text input where Return creates a new line, Fn-Return or Enter often submit the dialog itself (I use this often in the git client application Tower).

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Oh, interesting! I didn’t think of that, but it doesn’t surprise me that Keyboard Maestro can see it as a device key.

Good point! The Return key on the main keyboard is not the same as the Enter key on a numeric keypad, and indeed, Fn-Return sends the Enter keypress, as you can see at this site:

Worth mentioning an app called Fluor

A handy tool for macOS allowing you to switch Fn keys’ mode based on active application.

https://github.com/Pyroh/Fluor

So in editors I have them work as Function keys and in other apps as the standard media controls.

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You mention that it’s also called the Globe key. I think the reason is because it’s used to switch between languages when typing (which you can also do with CMD-Shift). It does the exact same thing with either key combination on my keyboard, switching between Japanese and English.

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I never tried the other combinations (other than just tapping Globe to switch languages). The Fn+H and Fn+N seem convenient!

My main “use” of the fn key on my Macally ergonomic keyboard is to accidentally hit it about once a day, which brings up the Spotlight Search popup. Perhaps some default setting for it is “fn” = find? But no one has mentioned that as a result of fn usage. I find that a bit odd.

Interesting. I wonder if that’s hard-coded into the Macally keyboard since I don’t see any way to trigger Spotlight with just the Fn key otherwise. Can you reset what it does in System Settings?

It might be. I have an old Macally keyboard (an iMediaKey, which isn’t even on their web site anymore). It has 19 media keys that don’t do anything without proprietary driver software.

I just tested it out on my modern Mac running Ventura (I’m actually writing this paragraph with it), and those media keys do absolutely nothing. I can’t even type them into the Keyboard system settings panel to assign them to something. So they’re very proprietary.

So this behavior might be something similar. Is there a Macally driver installed that might be providing this feature? If so, it may have a settings page you can use to change that behavior.

Just now noticing that the Fn -up and -down arrows on my Logitech K780 are set to adjust screen brightness. Maybe that’s because the top-row F keys include switching between devices, so there’s no room there for brightness?