Dual-Function Keys

Dual-function keys are keys that combine a TAP and a MOD/LAYER.

Simply put, when a dual-function key is tapped, it produces a single keystroke (TAP). However, when it is held down or used in combination with another key, it functions as a modifier key or layer access (MOD/LAYER).


Traditional keys do repeat themselves when holded but dual-function keys activate their MOD/LAYER effect in that situation.

To auto-repeat a dual-function key, first do a TAP, then hold.

Tip: You can also auto-repeat Space and Backspace by shifting them!

Pending MODs 🖱

Pending MODs are MODs on dual-function keys that are fired immediately at keypress in order to be used in conjunction with a mouse click. If the MOD is not used and the key is relased quickly, the MOD will be cancelled and the TAP will be sent instead.

However, certain applications respond to the release of the MODs themselves, which interferes with pending MODs:

  • Microsoft Windows launches the start menu when releasing Left Super
    • Some Linux window managers also use that shortcut for their menu
  • VirtualBox unfocuses the Virtual Machine when Right Control is released

Due to these interactions, only the Left Shift and Left Control pending MODs are enabled by default. If your requirements differ or if you use your mouse with your left hand, you can adjust this setting in the System Layer.

Opposite MODs as TAPs

When initiating a key combination with a MOD, all dual-function keys with MODs on the opposite side will function solely as TAP keys. This allows for the immediate activation of the combination upon key press on the opposite side.

In the case of 3-key combinations (involving two MODs), such as Super + Shift + ... or Control + Shift + ..., both MODs need to be pressed with the same hand, while the second completes the combination with a TAP key. The ADM42 has been designed to simplify such combinations by providing Shift accessible on both thumbs.

Alt keys are not dual-function keys and are not concerned by this logic.