Building and Flashing


From here on, building and flashing ZMK should all be done from the app/ subdirectory of the ZMK checkout:

cd app

To build for your particular keyboard, the behaviour varies slightly depending on if you are building for a keyboard with an onboard MCU, or one that uses an MCU board addon.

Keyboard (Shield) + MCU Board

ZMK treats keyboards that take an MCU addon board as shields, and treats the smaller MCU board as the true board

Given the following:

  • MCU Board: Proton-C
  • Keyboard PCB: kyria_left
  • Keymap: default

You can build ZMK with the following:

west build -b proton_c -- -DSHIELD=kyria_left

Keyboard With Onboard MCU

Keyboards with onboard MCU chips are simply treated as the board as far as Zephyr™ is concerned.

Given the following:

  • Keyboard: Planck (rev6)
  • Keymap: default

you can build ZMK with the following:

west build -b planck_rev6

Pristine Building

When building for a new board and/or shield after having built one previously, you may need to enable the pristine build option. This option removes all existing files in the build directory before regenerating them, and can be enabled by adding either --pristine or -p to the command:

west build -p -b proton_c -- -DSHIELD=kyria_left

Building For Split Keyboards


For split keyboards, you will have to build and flash each side separately the first time you install ZMK.

By default, the build command outputs a single .uf2 file named zmk.uf2 so building left and then right immediately after will overwrite your left firmware. In addition, you will need to pristine build each side to ensure the correct files are used. To avoid having to pristine build every time and separate the left and right build files, we recommend setting up separate build directories for each half. You can do this by using the -d parameter and first building left into build/left:

west build -d build/left -b nice_nano -- -DSHIELD=kyria_left

and then building right into build/right:

west build -d build/right -b nice_nano -- -DSHIELD=kyria_right

This produces left and right subfolders under the build directory and two separate .uf2 files. For future work on a specific half, use the -d parameter again to ensure you are building into the correct location.

Building from zmk-config Folder

Instead of building .uf2 files using the default keymap and config files, you can build directly from your zmk-config folder by adding -DZMK_CONFIG="C:/the/absolute/path/config" to your west build command. Notice that this path should point to the folder labelled config within your zmk-config folder.

For instance, building kyria firmware from a user myUser's zmk-config folder on Windows 10 may look something like this:

west build -b nice_nano -- -DSHIELD=kyria_left -DZMK_CONFIG="C:/Users/myUser/Documents/Github/zmk-config/config"


Once built, the previously supplied parameters will be remembered so you can run the following to flash your board with it in bootloader mode:

west flash

For boards that have drag and drop .uf2 flashing capability, the .uf2 file to flash can be found in build/zephyr (or build/left|right/zephyr if you followed the instructions for splits) and is by default named zmk.uf2.