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ZMK State Of The Firmware #5

· 8 min read
Pete Johanson

Welcome to the fifth ZMK "State Of The Firmware" (SOTF)!

This update will cover all the major activity since SOTF #4. That was over a year ago, so lots to cover!

Recent Activity

Here's a summary of the various major changes since last time, broken down by theme:


Since last time, there have been several new powerful keymap features and behaviors added, including several asked for features, such as tap-dance and macros.

Caps Word

petejohanson added the caps word behavior, i.e. &caps_word, in #823 that allows toggling a mode where all all alpha characters are sent to the host capitalized until a non-alpha, non-"continue list" keycode is sent. This can be useful for typing things like CONFIG_ENABLE_CAPS_WORD without having to hold down shift. This is similar in spirit to using the caps lock key, but with the added benefit of turning itself off automatically.

Key Repeat

petejohanson added the new key repeat behavior in #1034 to allow repeating the last sent key-press again, including any modifiers that were applied to that key press. It can be added to your keymap using the simple &key_repeat reference.


petejohanson, taking heavy inspiration on the initial work from okke-formsma, added macro support in #1168. Several common patterns are documented, but one example, changing the underglow color as you activate/deactivate a layer, looks like:

wait-ms = <0>;
tap-ms = <0>;
= <&macro_press &mo 1>
, <&macro_tap &rgb_ug RGB_COLOR_HSB(128,100,100)>
, <&macro_pause_for_release>
, <&macro_release &mo 1>
, <&macro_tap &rgb_ug RGB_COLOR_HSB(300,100,50)>;

Tap Dance

kurtis-lew worked diligently to add the tap-dance behavior in #1139, allowing different behaviors to be invoked based on the number of times a user taps a single key in their keymap, e.g.

/ {
behaviors {
td0: tap_dance_0 {
compatible = "zmk,behavior-tap-dance";
#binding-cells = <0>;
tapping-term-ms = <200>;
bindings = <&kp N1>, <&kp N2>, <&kp N3>;

keymap {
compatible = "zmk,keymap";

default_layer {
bindings = <

Conditional Layers

bcat added conditional layers in #830 as a generalized version of the common "adjust layer" pattern on smaller keyboards.


/ {
conditional_layers {
compatible = "zmk,conditional-layers";
tri_layer {
if-layers = <1 2>;
then-layer = <3>;


mcrosson added the layer specific combos in #661, so users can make certain combos only triggerable when the layers set for the combo are active.

This is used by the ZMK implementation of ARTSEY extensively.

Sticky Keys

okke-formsma updated sticky keys in #1122 to add the ignore-modifiers; property; when set, sticky keys won't release when other modifiers are pressed. This allows you to combine sticky modifiers, which is popularly used with "callum-style mods".

Hold-Tap Improvements

jmding8 added an additional positional hold-tap configuration in #835 to help certain sequences produce the expected results.

jmding8 also added an additional hold-tap flavor: tap-unless-interrupted in #1018 which works very well with the new positional hold-tap config.

okke-formsma implemented retro-tap hold-tap property in #667

okke-formsma also added quick-tap-ms hold-tap property in #655

Apple Device Compatibility Improvements


petejohanson did some sleuthing and fixed a long standing problem with inconsistent pairing with macOS in [#946]]( With the changes, macOS more reliably pairs with ZMK devices.

Consumer (Media) Codes

Another persistent bug that Apple users experienced was related to crashes and problems with keyboard configurations, that was traced to an issue with ZMK's HID usage that was fixed by petejohanson in #726.

Debounce Enhancements

joelspadin applied some major enhancements to our debouncing approach to allow fine grained control of our debouncing in #888, including allowing eager debouncing which can reduce key press latency.

Split Improvements

Behavior Locality

The long awaited locality enhancement was finally merged by petejohanson in #547, allowing more fine grained control of where certain behaviors are invoked. Some key improvements thanks to the changes:

  • RGB Underglow behaviors now run globally, so enabling/disabling RGB, changing the color, animation, etc. applies to both sides of a split properly.
  • Reset/Bootloader behaviors now run wherever the key was pressed. For example, adding a &bootloader reference to the peripheral side of a split will now put that side of the split into the bootloader when pressed.

Split Connections

petejohanson also added fixes to improve split re-connection for certain scenarios in #984, helping ensure splits properly connect when one side or the other is reset.

Hardware Support


bortoz added single color backlight support in #904 for those keyboards that have it as an alternative to RGB underglow.

E-Paper Display (EPD) Driver

petejohanson worked with LOWPROKB to add support for the E-Paper Displays (EPD) in #895 used in keyboards like the Corne-ish Zen.

nRF VDDH Battery Sensing

joelspadin added a new sensor driver to support battery charge calculation by sensing voltage on the VDDH pin on nRF52 chips in #750, which is particularly useful for designs using "high voltage mode" with that SoC.



dxmh and caksoylar have joined the ZMK organization to help with documentation, and have been doing an amazing job adding new docs, and leading reviewing docs related PRs to free other contributors up to focus on other areas. It's been an incredible addition to ZMK!

NKRO Support

petejohanson's work on the HID foundation also included adding support for full NKRO HID in #726 that can be enabled by adding the following to your .conf file for your config:


Power Profiler

It's been live for a while, but nicell added an amazing power profiler in #312 to allow users to estimate their battery life for various hardware configurations.

Min/Max Underglow Brightness

malinges added support for configuring min/max underglow brightness in #944 by setting the values in your .conf file as percentages of full:


This can be useful to be sure that lowering brightness doesn't set the brightness to zero, and raising the brightness doesn't consume too much power.

Zephyr 3.0

petejohanson helped prepare and test the upgrade of ZMK to Zephyr 3.0 in #1143. The updated Zephyr release brings with it some key BLE stability fixes, as well as various other core improvements that improve ZMK. This was a huge undertaking!

New Shields

New Boards

Board/Shield Metadata

nicell and petejohanson worked together in #883 to settle on a metadata format that is used to document every board and shield. This now drives automatic generation of our supported hardware page and our more nuanced GH Actions automation for testing changes to ZMK.

Coming Soon!

Some items listed in the last coming soon section are still under active development.

  • RP2040 support
  • Peripheral rotary encoder support
  • Caps/Scroll/Num Lock LED support
  • Mouse Keys
  • Wired split support
  • More modular approach to external boards/shields, custom code, user keymaps, etc.
  • More shields and boards


Some statistics of interest for ZMK:

  • GitHub (lifetime stats)
    • 105 Contributors
    • 791 Closed PRs
    • 849 Stars
    • 832 Forks
  • Discord Chat
    • 3430 total registered
  • Website (last 30 days)
    • 35.9K page views
    • 3.29K new users


As we approach the two year birthday for ZMK, I am reminded of how far we have come in such a short time, in large part thanks to the amazing community that has grown around it. I am so grateful to have so many contributors, testers, and user believing in the project and helping make it a joy to work on.

Article Updates

  • 12/2023: Removed the deprecated label property from code snippets.