How to remapping keys on macOS without thirdparty applications.

remapping-keys-via-hidutil.md

How to remapping keys on macOS without thirdparty applications.

You could remapping keys via the macOS embedded command line tool hidutil.

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Key IDs Table

Usage	Usage ID (hex)	Usage	Usage ID (hex)	Usage	Usage ID (hex)	Usage	Usage ID (hex)
Keyboard a and A	0x700000004	Keyboard 5 and %	0x700000022	Keyboard F7	0x700000040	Keypad 6 and Right Arrow	0x70000005E
Keyboard b and B	0x700000005	Keyboard 6 and ^	0x700000023	Keyboard F8	0x700000041	Keypad 7 and Home	0x70000005F
Keyboard c and C	0x700000006	Keyboard 7 and &	0x700000024	Keyboard F9	0x700000042	Keypad 8 and Up Arrow	0x700000060
Keyboard d and D	0x700000007	Keyboard 8 and *	0x700000025	Keyboard F10	0x700000043	Keypad 9 and Page Up	0x700000061
Keyboard e and E	0x700000008	Keyboard 9 and (	0x700000026	Keyboard F11	0x700000044	Keypad 0 and Insert	0x700000062
Keyboard f and F	0x700000009	Keyboard 0 and )	0x700000027	Keyboard F12	0x700000045	Keypad . and Delete	0x700000063
Keyboard g and G	0x70000000A	Keyboard Return (Enter)	0x700000028	Keyboard Print Screen	0x700000046	Keyboard Non-US \ and |	0x700000064
Keyboard h and H	0x70000000B	Keyboard Escape	0x700000029	Keyboard Scroll Lock	0x700000047	Keyboard Application	0x700000065
Keyboard i and I	0x70000000C	Keyboard Delete (Backspace)	0x70000002A	Keyboard Pause	0x700000048	Keyboard Power	0x700000066
Keyboard j and J	0x70000000D	Keyboard Tab	0x70000002B	Keyboard Insert	0x700000049	Keypad =	0x700000067
Keyboard k and K	0x70000000E	Keyboard Spacebar	0x70000002C	Keyboard Home	0x70000004A	Keyboard F13	0x700000068
Keyboard l and L	0x70000000F	Keyboard - and _	0x70000002D	Keyboard Page Up	0x70000004B	Keyboard F14	0x700000069
Keyboard m and M	0x700000010	Keyboard = and +	0x70000002E	Keyboard Delete Forward	0x70000004C	Keyboard F15	0x70000006A
Keyboard n and N	0x700000011	Keyboard [ and {	0x70000002F	Keyboard End	0x70000004D	Keyboard F16	0x70000006B
Keyboard o and O	0x700000012	Keyboard ] and }	0x700000030	Keyboard Page Down	0x70000004E	Keyboard F17	0x70000006C
Keyboard p and P	0x700000013	Keyboard \ and |	0x700000031	Keyboard Right Arrow	0x70000004F	Keyboard F18	0x70000006D
Keyboard q and Q	0x700000014	Keyboard Non-US # and ~	0x700000032	Keyboard Left Arrow	0x700000050	Keyboard F19	0x70000006E
Keyboard r and R	0x700000015	Keyboard ; and :	0x700000033	Keyboard Down Arrow	0x700000051	Keyboard F20	0x70000006F
Keyboard s and S	0x700000016	Keyboard ' and "	0x700000034	Keyboard Up Arrow	0x700000052	Keyboard F21	0x700000070
Keyboard t and T	0x700000017	Keyboard Grave Accent and Tilde	0x700000035	Keypad Num Lock and Clear	0x700000053	Keyboard F22	0x700000071
Keyboard u and U	0x700000018	Keyboard , and "<"	0x700000036	Keypad /	0x700000054	Keyboard F23	0x700000072
Keyboard v and V	0x700000019	Keyboard . and ">"	0x700000037	Keypad *	0x700000055	Keyboard F24	0x700000073
Keyboard w and W	0x70000001A	Keyboard / and ?	0x700000038	Keypad -	0x700000056	Keyboard Left Control	0x7000000E0
Keyboard x and X	0x70000001B	Keyboard Caps Lock	0x700000039	Keypad +	0x700000057	Keyboard Left Shift	0x7000000E1
Keyboard y and Y	0x70000001C	Keyboard F1	0x70000003A	Keypad Enter	0x700000058	Keyboard Left Alt	0x7000000E2
Keyboard z and Z	0x70000001D	Keyboard F2	0x70000003B	Keypad 1 and End	0x700000059	Keyboard Left GUI	0x7000000E3
Keyboard 1 and !	0x70000001E	Keyboard F3	0x70000003C	Keypad 2 and Down Arrow	0x70000005A	Keyboard Right Control	0x7000000E4
Keyboard 2 and @	0x70000001F	Keyboard F4	0x70000003D	Keypad 3 and Page Down	0x70000005B	Keyboard Right Shift	0x7000000E5
Keyboard 3 and #	0x700000020	Keyboard F5	0x70000003E	Keypad 4 and Left Arrow	0x70000005C	Keyboard Right Alt	0x7000000E6
Keyboard 4 and $	0x700000021	Keyboard F6	0x70000003F	Keypad 5	0x70000005D	Keyboard Right GUI	0x7000000E7

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Remapping keys

If you want to remap the key 'CapsLock(0x700000039)' to 'F18(0x70000006D)'. type below in terminal

$ hidutil property --set '{"UserKeyMapping":[
  {
    "HIDKeyboardModifierMappingSrc": 0x700000039, # source key
    "HIDKeyboardModifierMappingDst": 0x70000006D  # destination key
  }
]}'

Checking remapped keys

$ hidutil property --get "UserKeyMapping"
# If there is no remapped key, you will receive (null).

How to persist remapping keys

Above way will be undone whenever you reboot your Mac, so one way to persist the remapping is to run the hidutil command every time your Mac boots. For that, we can rely on Launch Agents.

Create a file named ~/Library/LaunchAgents/com.example.KeyRemapping.plist, that makes macOS run the hidutil tool every time it starts up.

<!--
  Put this file in ~/Library/LaunchAgents/com.example.KeyRemapping.plist to
  automatically remap your keys when macOS starts.
-->
<?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>Label</key>
    <string>com.example.KeyRemapping</string>
    <key>ProgramArguments</key>
    <array>
        <string>/usr/bin/hidutil</string>
        <string>property</string>
        <string>--set</string>
        <string>{"UserKeyMapping":[
          {
            "HIDKeyboardModifierMappingSrc": 0x700000039,
            "HIDKeyboardModifierMappingDst": 0x70000006D
          }
        ]}</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
</dict>
</plist>

References

• https://chuyeow.wtf/2020/06/24/remapping-keys-on-macos
• https://developer.apple.com/library/archive/technotes/tn2450/_index.html#//apple_ref/doc/uid/DTS40017618-CH1-KEY_TABLE_USAGES
• https://opensource.apple.com/source/launchd/launchd-257/launchd/doc/HOWTO.html

For anyone that doesn't want to do all this manually anymore, I built a native swift app for remapping all the keys. Clicking Save will save the changes for the current session and also save/update the plist file as a launch daemon.
It needs accessibility permission to perform hidutil changes on the fly via the IOKit.hid API.
It will also ask to install a helper tool on launch so it can perform the launch daemon changes without asking for password every single time.

https://github.com/alienator88/PearHID
It's the first version/beta right now, so might have a bug or two, but would love it if anybody is willing to test it out.

@alienator88 thats a lot for this tool, man! Really appreciate my saved time!

You're welcome! Thanks for testing it out :)