How do you make the fn keyboard button work like a Ctrl button?

Question

I'm used to having the Control button at the bottom left corner of the keyboard. It's a little annoying to be pressing Fn + Tab when I wanted a Control + Tab and the position of the Control button in the new Mac keyboard layout is just very uncomfortable for any finger to reach.

Does anybody know how you can make the Control and Fn buttons change function like how you can change the modifier keys in System Preferences?

Is it possible to map fn key only for combinations of alphanumeric keys? I would like fn key behave like control key only when pressed with combinations fn+a, fn+b..., fn+z, fn+1...fn+0. I would like still to get fn+F1, fn+F2... to work as factory default. — Marecky, Dec 14 '21 at 13:29
@Mahdi would like to know that as well. Worst part is their larger num pad keyboard has a big ctrl button and the fn key is somewhere else entirely. Consistency at its finest. — Martin Braun, Aug 13 '23 at 17:38

score 22 · Answer 1 · edited Jan 23 '18 at 20:10

22

Download and install Karabiner
Open Karabiner Elements and set the Target Device in the dropdown
Map fn to left_control and left_control to fn as below

edited Jan 23 '18 at 20:10

grg

201,078

answered Jan 23 '18 at 19:07

WiredIn

320

karabiner is great and does all things – minseong Feb 20 '19 at 04:55
is apple a1243 or a1242 supported? – Alexander Myravjev Apr 28 '20 at 01:17
1

I'm on Catalina 10.15.7. This works for most of my uses but now when I press 'fn' (that should now behave like 'ctrl') the Touch Bar still reacts to that and in my set-up the function 'buttons' are replaced with multimedia ones. So I cannot press, say, 'fn'+'f12' because as soon as I press 'fn' 'f12' disappears. Any way to stop that? – Johnny Baloney Apr 08 '21 at 15:32
@JohnnyBaloney: the same problem! – Anh-Thi DINH May 10 '21 at 13:39

score 19 · Accepted Answer · answered Jan 24 '18 at 04:45

19

Not sure which OS this started appearing in but in macOS 10.13, this can be customized in System Preferences > Keyboard > Modifier Keys:

answered Jan 24 '18 at 04:45

radj

736

15

I'm running 10.13.3 but do not see the fn Key in the modifier key window. Was it removed again? – Spork Mar 27 '18 at 15:26
@Spork I am also on 10.13.3 right now and I can still see the fn key modifiers. – radj Apr 04 '18 at 03:50
7

That's peculiar. I double checked, but see only 4 options. It also doesn't show up on google images for 'modifier keys' (the only exception being the image in this answer). Are you sure it isn't something you've installed? – Spork Apr 04 '18 at 07:43
19

Sadly this only works to map fn to ctrl but it's impossible to map ctrl to fn. – andresp Jul 02 '18 at 13:21
do you know if this works for a laptop keyboard or just external one? – William Aug 24 '18 at 23:55
@William in my setup, it works for both. – radj Aug 27 '18 at 04:41
2

I'm in 10.14.2 and also only seeing 4 options (fn not being one of them). – rept Jan 07 '19 at 23:49
I can confirm the issue that others are mentioning in the comments (in Mojave, 10.14.2), strangely enough no key except the real fn key can be mapped to fn; you can map fn to command but not command to fn. I guess this is okay for me since I rarely use fn. – jrh Jan 13 '19 at 02:26
1

This, plus binding Caps Lock › Esc, is an absolute gamechanger for Vim – iono Jul 11 '19 at 06:33
3

Apple doing it again, can remap fn to ctrl but not the otherway around, truly geniuses ahead of its time. – Ivan Castellanos Nov 24 '19 at 01:40
On my macbook pro keyboard (QWERTY) I have 4 options. On my iMac's external Apple keyboard with numpad (AZERTY) I have the above 5 options. Both systems run macOS 10.15.5. Not sure if it's external vs laptop keyboard, or related to the keyboard layout/language. If it's the former, it would be kind of ironic, since on the external keyboard the Fn key is near the numpad and not located near the ctrl key. – Rabarberski Jul 10 '20 at 12:52
On my MacBook Air I have 5 options including fn key, but on my MacBook Pro with the same operating system Mac OS 10.15.7 I only have 4 options NOT including the fn key – HerrNilsson Mar 30 '21 at 18:01
I don't see the FN key on mine either in that option menu. (Macbook pro 2019). So ridiculous. – munchschair Apr 13 '21 at 13:40

eqyiel · Answer 3 · 2020-07-26T03:06:19.153

This is my white whale. I can't use Emacs without the control key being on the left hand side. Recently I got a new MacBook so I had a chance to do this without Karabiner.

This is what worked for me to rebind the function key to control (for the built-in keyboard only), on macOS 10.15.6.

hidutil property --matching '{ "ProductID": 0x027e }' --set '{
  "UserKeyMapping": [
    {
      "HIDKeyboardModifierMappingDst": 30064771300,
      "HIDKeyboardModifierMappingSrc": 1095216660483
    },
    {
      "HIDKeyboardModifierMappingDst": 30064771296,
      "HIDKeyboardModifierMappingSrc": 280379760050179
    }
  ]
}'

Verify it with hidutil property --matching '{ "ProductID": 0x027e }' --get "UserKeyMapping".

How I found these keycodes

I've both seen the option to change the Function (fn) Key and not seen the option to change the Function (fn) Key on the same computer, using the same version of macOS. Take it with a grain of salt, but I can consistently get the variant with the Function (fn) Key option to appear if I:

Have an external keyboard attached, via a USB-Type C hub
Open the Keyboard → Keyboard → Modifier Keys
Lock the screen using the external keyboard
Walk away for some time (wait until the computer sleeps)
Wake the computer by pressing a key on the external keyboard and use Touch ID to log in
Now the Modifier Keys preference has the Function (fn) Key option. While in this state, change the behaviour of the function key using the drop down list (I chose ^ Control)
Copy ~/Library/Preferences/ByHost/.GlobalPreferences.${__UUID__}.plist (described here) somewhere else temporarily
Convert the binary PList to XML: plutil -convert xml1 .GlobalPreferences.${__UUID__}.plist

Contents of that file are:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>com.apple.keyboard.modifiermapping.1452-638-0</key>
    <array>
        <dict>
            <key>HIDKeyboardModifierMappingDst</key>
            <integer>30064771300</integer>
            <key>HIDKeyboardModifierMappingSrc</key>
            <integer>1095216660483</integer>
        </dict>
        <dict>
            <key>HIDKeyboardModifierMappingDst</key>
            <real>30064771296</real>
            <key>HIDKeyboardModifierMappingSrc</key>
            <integer>280379760050179</integer>
        </dict>
    </array>
</dict>
</plist>

This page shows up if you search for these HIDKeyboardModifierMappingSrc and says that 1095216660483 is for the left function key, 280379760050179 is for the right.

I thought I was going crazy so I took some screenshots for proof:

Modifier Keys preference pane without the `Function (fn) Key` option

Modifier Keys preference pane with the `Function (fn) Key` option

About `ProductID`

You can find the Product ID associated with your keyboard using the System Report button: Apple menu → System Report → Hardware → USB.

If you use the --matching parameter to hidutil using a specific Product ID, the changes will affect that piece of hardware only. For example, maybe you want to change the layout of the built-in keyboard, but not an external one.

Excellent post, thanks very much - this answer deserves to be much higher as it does exactly what is asked without the overhead of additional software. — geedoubleya, Sep 05 '20 at 20:21
Nice aswer! But it didn't work, unfortunately. Fn started to work as Ctrl, but kept also working as Fn, and Ctrl didn't work as Fn. I'm using the MacBook Pro 16 here, so it seems there is some hardwired stuff in this hardware, probably related to the touch bar. — Bruno Medeiros, Sep 08 '20 at 03:57
I had the same problem as @BrunoJCM. This solution allowed me to map the Fn key to Ctrl, but it didn't map the Ctrl key to Fn. And when I press the Fn key, the function commands still pop up on the touch bar. — wheeler, Nov 03 '21 at 23:17
This is super nice solution ! Thank you! I value your process of finding out the right things. Now, if we need other codes, one can use https://hidutil-generator.netlify.app to find out the mapping (not my work). — Ciprian Tomoiagă, Nov 10 '21 at 15:00
@wheeler it seems some keyboards generate different codes for Fn. I've found out form here: https://github.com/amarsyla/hidutil-key-remapping-generator/issues/3 — Ciprian Tomoiagă, Nov 10 '21 at 15:01
Is it possible only to allow fn+tab behave as control+tab? That would help me a lot, I don't need more mapping, just this one. — Marecky, Dec 14 '21 at 13:41

Guido Preite · Answer 4 · 2013-04-16T11:13:51.870

6

you can use KeyRemap4MacBook

http://pqrs.org/macosx/keyremap4macbook/

you can find the included prepared settings list at this address:

http://pqrs.org/macosx/keyremap4macbook/list.html.en

as you can see there is the setting for Fn Key

edited Apr 16 '13 at 11:13

answered Apr 16 '13 at 06:28

Guido Preite

3,541

Thank you! Worked like a charm. And it has many other useful settings, too! – radj Apr 16 '13 at 09:21
As a heads up, this has been replaced by Karabiner-Elements – jkmartindale Nov 30 '21 at 00:19

score 3 · Answer 5 · edited Nov 30 '21 at 01:12

I was happy, but then not as much. I just bought a Logitech K850 keyboard. Has a nice shape to help with wrist issues (for another time). Has keys from left as:

ctrl    fn    alt opt    cmd <butterfly>

Tried Karabiner but it didn't seem to work (tested by using ctrl-F in vi/vim). Then I found this document https://karabiner-elements.pqrs.org/docs/getting-started/features which lists a limitation.

Karabiner-Elements cannot modify the fn key on non Apple keyboards such as Logitech keyboards.

Not for Logitech. Ouch. Other suggestions? Back to best buy again? I'm really just looking for a mac layout keyboard with full size keys. I don't care about the num pad, etc. on right side. The K850 looked good except for this issue. Some gentle ergonomics help is good.

I am still using the K850 after more than a year. Though I cannot swap the ctrl and fn keys, I am very happy with this keyboard. I've grown accustomed to the layout and the feel is "oh so much" better than the macbook air 2018 laptop keyboard. FYI. — Alan Carwile, Apr 28 '20 at 16:31

score 3 · Answer 6 · answered Aug 04 '22 at 07:58

3

I'm a new Mac user so I don't know much about how this was solved before. But this seems to be fixed in MacOs Monterey 12.5 (MacBook Pro 16'' 2021). No third application required :)

answered Aug 04 '22 at 07:58

yin_yang2k

31

score 2 · Answer 7 · edited Nov 30 '21 at 06:52

2

You could also add this to private.xml:

<autogen>__KeyToKey__ KeyCode::FN, KeyCode::CONTROL_L</autogen>
<autogen>__KeyToKey__ KeyCode::CONTROL_L, KeyCode::FN</autogen>

See the source for the key code values and predefined settings.

edited Nov 30 '21 at 06:52

jkmartindale

121

answered Apr 16 '13 at 12:33

Lri

105,117

score 1 · Answer 8 · answered Feb 01 '21 at 19:59

1

In addition to trackpad gestures, Better Touch Tool allows you to remap individual keyboard combinations. I use it to remap fn ⇥ to ⌃ ⇥ and fn ⇧ ⇥ to ⌃ ⇧ ⇥.

answered Feb 01 '21 at 19:59

Greg Perham

1,495

ms350125 · Answer 9 · 2021-10-01T21:30:52.727

1

Looks like the one way to make Karabiner work with Logitech keyboards is to uninstall Logi Options, but then:

the keyboard will behave like standard Apple keyboard - the mapping of function keys will differ from pictograms (I guess these can be remapped with Karabiner)
you will need to find another way to configure mouse buttons 3-5.

edited Oct 01 '21 at 21:30

answered Oct 01 '21 at 21:00

ms350125

11

score 0 · Answer 10 · edited Oct 23 '23 at 14:07

0

The hidutil-key-remapping-generator worked perfectly for me. You can access the tool online from hidutil key remapping generator for MacOS and copy the configuration to

~/Library/LaunchAgents/com.local.KeyRemapping.plist

edited Oct 23 '23 at 14:07

agarza

2,274

answered Oct 23 '23 at 12:20

lovemarcus

1

How do you make the fn keyboard button work like a Ctrl button?

10 Answers10

How I found these keycodes

Modifier Keys preference pane without the `Function (fn) Key` option

Modifier Keys preference pane with the `Function (fn) Key` option

About `ProductID`

Linked

Related

How do you make the fn keyboard button work like a Ctrl button?

10 Answers10

How I found these keycodes

Modifier Keys preference pane without the Function (fn) Key option

Modifier Keys preference pane with the Function (fn) Key option

About ProductID

Linked

Related

Modifier Keys preference pane without the `Function (fn) Key` option

Modifier Keys preference pane with the `Function (fn) Key` option

About `ProductID`