Unicode 
With a little help from your OS, practically any Unicode character can be input using your keyboard.
Caveats 
There are some limitations to this feature. Because there is no "standard" method of Unicode input across all operating systems, each of them require their own setup process on both the host and in the firmware, which may involve installation of additional software. This also means Unicode input will not "just work" when the keyboard is plugged into another device.
Usage 
The core Unicode API can be used purely programmatically. However, there are also additional subsystems which build on top of it and come with keycodes to make things easier. See below for more details.
Add the following to your keymap's rules.mk:
UNICODE_COMMON = yesBasic Configuration 
Add the following to your config.h:
| Define | Default | Description | 
|---|---|---|
| UNICODE_KEY_MAC | KC_LEFT_ALT | The key to hold when beginning a Unicode sequence with the macOS input mode | 
| UNICODE_KEY_LNX | LCTL(LSFT(KC_U)) | The key to tap when beginning a Unicode sequence with the Linux input mode | 
| UNICODE_KEY_WINC | KC_RIGHT_ALT | The key to hold when beginning a Unicode sequence with the WinCompose input mode | 
| UNICODE_SELECTED_MODES | -1 | A comma separated list of input modes for cycling through | 
| UNICODE_CYCLE_PERSIST | true | Whether to persist the current Unicode input mode to EEPROM | 
| UNICODE_TYPE_DELAY | 10 | The amount of time to wait, in milliseconds, between Unicode sequence keystrokes | 
Audio Feedback 
If you have the Audio feature enabled on your board, you can configure it to play sounds when the input mode is changed.
Add the following to your config.h:
| Define | Default | Description | 
|---|---|---|
| UNICODE_SONG_MAC | n/a | The song to play when the macOS input mode is selected | 
| UNICODE_SONG_LNX | n/a | The song to play when the Linux input mode is selected | 
| UNICODE_SONG_BSD | n/a | The song to play when the BSD input mode is selected | 
| UNICODE_SONG_WIN | n/a | The song to play when the Windows input mode is selected | 
| UNICODE_SONG_WINC | n/a | The song to play when the WinCompose input mode is selected | 
Input Subsystems 
Each of these subsystems have their own pros and cons in terms of flexibility and ease of use. Choose the one that best fits your needs.
This is the easiest to use, albeit somewhat limited. It supports code points up to U+7FFF, which covers characters for most modern languages (including East Asian), as well as many symbols, but does not include emoji.
To enable Basic Unicode, add the following to your rules.mk:
UNICODE_ENABLE = yesYou can then add UC(c) keycodes to your keymap, where c is the code point of the desired character (in hexadecimal - the U+ prefix will not work). For example, UC(0x40B) will output Ћ, and UC(0x30C4) will output ツ.
Input Modes 
Unicode input works by typing a sequence of characters, similar to a macro. However, since this sequence depends on your OS, you will need to prepare both your host machine and QMK to recognise and send the correct Unicode input sequences respectively.
To set the list of enabled input modes, add the UNICODE_SELECTED_MODES define to your keymap's config.h, for example:
#define UNICODE_SELECTED_MODES UNICODE_MODE_LINUX
// or
#define UNICODE_SELECTED_MODES UNICODE_MODE_MACOS, UNICODE_MODE_WINCOMPOSEThese modes can then be cycled through using the UC_NEXT and UC_PREV keycodes. You can also switch to any input mode, even if it is not specified in UNICODE_SELECTED_MODES, using their respective keycodes.
If your keyboard has working EEPROM, it will remember the last used input mode and continue using it on the next power up. This can be disabled by defining UNICODE_CYCLE_PERSIST to false.
Mode Name: UNICODE_MODE_MACOS
macOS has built-in support for Unicode input as its own input source. It supports all possible code points by way of surrogate pairs for code points above U+FFFF.
To enable, go to System Preferences → Keyboard → Input Sources, then add Unicode Hex Input to the list (under Other), and activate it from the input dropdown in the menu bar. Note that this may disable some Option-based shortcuts such as Option+Left and Option+Right.
Keycodes 
| Key | Aliases | Description | 
|---|---|---|
| UC(c) | Send Unicode code point c, up to0x7FFF | |
| UM(i) | Send Unicode code point at index iinunicode_map | |
| UP(i, j) | Send Unicode code point at index i, orjif Shift/Caps is on | |
| QK_UNICODE_MODE_NEXT | UC_NEXT | Cycle through selected input modes | 
| QK_UNICODE_MODE_PREVIOUS | UC_PREV | Cycle through selected input modes in reverse | 
| QK_UNICODE_MODE_MACOS | UC_MAC | Switch to macOS input | 
| QK_UNICODE_MODE_LINUX | UC_LINX | Switch to Linux input | 
| QK_UNICODE_MODE_WINDOWS | UC_WIN | Switch to Windows input | 
| QK_UNICODE_MODE_BSD | UC_BSD | Switch to BSD input (not implemented) | 
| QK_UNICODE_MODE_WINCOMPOSE | UC_WINC | Switch to Windows input using WinCompose | 
| QK_UNICODE_MODE_EMACS | UC_EMAC | Switch to emacs ( C-x-8 RET) | 
API 
uint8_t get_unicode_input_mode(void) 
Get the current Unicode input mode.
Return Value 
The currently active Unicode input mode.
void set_unicode_input_mode(uint8_t mode) 
Set the Unicode input mode.
Arguments 
- uint8_t mode
 The input mode to set.
void unicode_input_mode_step(void) 
Change to the next Unicode input mode.
void unicode_input_mode_step_reverse(void) 
Change to the previous Unicode input mode.
void unicode_input_mode_set_user(uint8_t input_mode) 
User-level callback, invoked when the input mode is changed.
Arguments 
- uint8_t input_mode
 The new input mode.
void unicode_input_mode_set_kb(uint8_t input_mode) 
Keyboard-level callback, invoked when the input mode is changed.
Arguments 
- uint8_t input_mode
 The new input mode.
void unicode_input_start(void) 
Begin the Unicode input sequence. The exact behavior depends on the currently selected input mode:
- macOS: Hold UNICODE_KEY_MAC
- Linux: Tap UNICODE_KEY_LNX
- WinCompose: Tap UNICODE_KEY_WINC, then U
- HexNumpad: Hold Left Alt, then tap Numpad +
- Emacs: Tap Ctrl+X, then 8, then Enter
This function is weakly defined, and can be overridden in user code.
void unicode_input_finish(void) 
Complete the Unicode input sequence. The exact behavior depends on the currently selected input mode:
- macOS: Release UNICODE_KEY_MAC
- Linux: Tap Space
- WinCompose: Tap Enter
- HexNumpad: Release Left Alt
- Emacs: Tap Enter
This function is weakly defined, and can be overridden in user code.
void unicode_input_cancel(void) 
Cancel the Unicode input sequence. The exact behavior depends on the currently selected input mode:
- macOS: Release UNICODE_KEY_MAC
- Linux: Tap Escape
- WinCompose: Tap Escape
- HexNumpad: Release Left Alt
- Emacs: Tap Ctrl+G
This function is weakly defined, and can be overridden in user code.
void register_unicode(uint32_t code_point) 
Input a single Unicode character. A surrogate pair will be sent if required by the input mode.
Arguments 
- uint32_t code_point
 The code point of the character to send.
void send_unicode_string(const char *str) 
Send a string containing Unicode characters.
Arguments 
- const char *str
 The string to send.
uint8_t unicodemap_index(uint16_t keycode) 
Get the index into the unicode_map array for the given keycode, respecting shift state for pair keycodes.
Arguments 
- uint16_t keycode
 The Unicode Map keycode to get the index of.
Return Value 
An index into the unicode_map array.
uint32_t unicodemap_get_code_point(uint8_t index) 
Get the code point for the given index in the unicode_map array.
Arguments 
- uint8_t index
 The index into the- unicode_maparray.
Return Value 
A Unicode code point value.
void register_unicodemap(uint8_t index) 
Send the code point for the given index in the unicode_map array.
Arguments 
- uint8_t index
 The index into the- unicode_maparray.
void ucis_start(void) 
Begin the input sequence.
bool ucis_active(void) 
Whether UCIS is currently active.
Return Value 
true if UCIS is active.
uint8_t ucis_count(void) 
Get the number of characters in the input sequence buffer.
Return Value 
The current input sequence buffer length.
bool ucis_add(uint16_t keycode) 
Add the given keycode to the input sequence buffer.
Arguments 
- uint16_t keycode
 The keycode to add. Must be between- KC_Aand- KC_Z, or- KC_1and- KC_0.
Return Value 
true if the keycode was added.
bool ucis_remove_last(void) 
Remove the last character from the input sequence buffer.
Return Value 
true if the sequence was not empty.
void ucis_finish(void) 
Mark the input sequence as complete, and attempt to match.
void ucis_cancel(void) 
Cancel the input sequence.
void register_ucis(void) 
Send the code point(s) for the given UCIS index.
Arguments 
- uint8_t index
 The index into the UCIS symbol table.