zmk/docs/docs/behaviors/mod-morph.md

title	sidebar_label
Mod-Morph Behavior	Mod-Morph

Summary

The Mod-Morph behavior sends a different keypress, depending on whether a specified modifier is being held during the keypress.

• If you tap the key by itself, the first keycode is sent.
• If you tap the key while holding the specified modifier, the second keycode is sent.

Mod-Morph

The Mod-Morph behavior acts as one of two keycodes, depending on if the required modifier is being held during the keypress.

Configuration

An example of how to implement the mod-morph "Grave Escape":

/ {
    behaviors {
        gresc: grave_escape {
            compatible = "zmk,behavior-mod-morph";
            label = "GRAVE_ESCAPE";
            #binding-cells = <0>;
            bindings = <&kp ESC>, <&kp GRAVE>;
            mods = <(MOD_LGUI|MOD_LSFT|MOD_RGUI|MOD_RSFT)>;
        };
    };
};

Note that this specific mod-morph exists in ZMK by default using code &gresc.

Behavior Binding

• Reference: &gresc
• Parameter: None

Example:

&gresc

Mods

This is how you determine what modifiers will activate the morphed version of the keycode.

Available Modifiers:

• MOD_LSFT
• MOD_RSFT
• MOD_LCTL
• MOD_RCTL
• MOD_LALT
• MOD_RALT
• MOD_LGUI
• MOD_RGUI

Example:

mods = <(MOD_LGUI|MOD_LSFT|MOD_RGUI|MOD_RSFT)>;

Advanced configuration

masked_mods

When a modifier specified in mods is being held, it won't be sent along with the morphed keycode if it is also part of masked_mods. To sent all modifiers along with the morphed keycode, set masked_mods to <0>. By default, masked_mods equals mods.

For example, the following configuration morphs LEFT_SHIFT + BACKSPACE into DELETE, and morphs RIGHT_SHIFT + BACKSPACE into RIGHT_SHIFT + DELETE.

/ {
    behaviors {
        bspc_del: backspace_delete {
            compatible = "zmk,behavior-mod-morph";
            label = "BACKSPACE_DELETE";
            #binding-cells = <0>;
            bindings = <&kp BACKSPACE>, <&kp DELETE>;
            mods = <(MOD_LSFT|MOD_RSFT)>;
            masked_mods = <(MOD_LSFT)>;
        };
    };
};

Limitations

In some circumstance, when the morphed keycode is a hold-tap, the modifier gets sent along with the hold-tap regardless of the specification of masked_mods.