ZMK Case Mode

A ZMK module that lets you type identifiers like snake_case, camelCase, PascalCase, kebab-case, and more; just by typing normally with spaces.

Activate a case mode, type words separated by space, and the module transforms each space into the appropriate delimiter or capitalizes the next letter. Inspired by ZMK's built-in caps-word - same idea of a smart mode that auto-deactivates, but for case styles.

Install

Add the module to your ZMK config manifest (config/west.yml):

manifest:
  remotes:
    - name: msmaili
      url-base: https://github.com/MSmaili
  projects:
    - name: zmk-case-mode
      remote: msmaili
      revision: main

Usage

Include the pre-defined behaviors and bind them in your keymap:

#include <behaviors/case_mode.dtsi>

/ {
    keymap {
        default_layer {
            bindings = <... &case_snake ...>;
        };
    };
};

Or via combos:

/ {
    combos {
        combo_snake {
            timeout-ms = <50>;
            bindings = <&case_snake>;
            key-positions = <1 2>;
        };
    };
};

Pre-defined Behaviors

Ready to use after including the dtsi. All pre-defined behaviors include numbers (N0-N9) and BACKSPACE in their continue-list. Create your own behavior if you want to remove it or add more keys like DELETE.

Binding	Produces	Example
&case_snake	snake_case	my_variable
&case_camel	camelCase	myVariable
&case_pascal	PascalCase	MyVariable
&case_kebab	kebab-case	my-variable
&case_screaming	SCREAMING_SNAKE	MY_VARIABLE

Custom Behaviors

Need dot.case, Train-Case, or something else? Define your own:

/ {
    behaviors {
        case_dot: case_dot {
            compatible = "zmk,behavior-case-mode";
            #binding-cells = <0>;
            delimiter = <DOT>;
            emit-delimiter;
            continue-list = <N1 N2 N3 N4 N5 N6 N7 N8 N9 N0 BACKSPACE>;
        };
    };
};

Path-style delimiters also work, for example:

/ {
    behaviors {
        case_path: case_path {
            compatible = "zmk,behavior-case-mode";
            #binding-cells = <0>;
            delimiter = <SLASH>;
            emit-delimiter;
        };
    };
};

Properties

Property	Type	Default	Description
delimiter	int	0	Keyboard keycode emitted on space, such as UNDERSCORE, MINUS, DOT, or SLASH. Set this when emit-delimiter is enabled.
emit-delimiter	boolean	false	Whether to send the delimiter. When false, space is swallowed.
capitalize-words	boolean	false	Capitalize the first letter of each word (after space).
capitalize-first	boolean	false	Capitalize the very first letter after activation.
capitalize-all	boolean	false	Capitalize every letter (for SCREAMING styles).
continue-list	array	none	Extra keycodes that don't deactivate case mode.

Boolean properties in devicetree are enabled by writing the property name alone, and disabled by omitting it.

Alpha keys (A-Z) always continue the mode. Everything else deactivates unless it's in continue-list.

How properties combine

Style	delimiter	emit-delimiter	capitalize-words	capitalize-first	capitalize-all
snake_case	UNDERSCORE	✓
camelCase			✓
PascalCase			✓	✓
kebab-case	MINUS	✓
SCREAMING_SNAKE	UNDERSCORE	✓			✓
dot.case	DOT	✓
Train-Case	MINUS	✓	✓	✓

Behavior Notes

• Press the case mode binding again to toggle it off.
• Activating one case mode deactivates any other active instance.
• Modifier chords (Ctrl/Alt/Gui + key) pass through without affecting case mode.
• Any key not in alpha (A-Z) or continue-list deactivates the mode and passes through normally.

Development

This module follows the ZMK module layout: https://zmk.dev/docs/development/module-creation