The PrefixLayer plugin allows you to easily create a keyboard layer designed for use with programs that use a prefix key, such as tmux or screen. When a key in a prefix layer is pressed, the prefix is injected first, then the key in that layer is pressed.

Using the plugin

You will need to define a keymap layer and configure the plugin to use that layer with a prefix key. You can then include the plugin’s header and set the .prefix_layers property.

#include <Kaleidoscope.h>
#include <Kaleidoscope-PrefixLayer.h>

enum {
};  // layers

static const kaleidoscope::plugin::PrefixLayer::Entry prefix_layers[] PROGMEM = {
  kaleidoscope::plugin::PrefixLayer::Entry(TMUX, LCTRL(Key_B)),


void setup() {
  PrefixLayer.prefix_layers = prefix_layers;
  PrefixLayer.prefix_layers_length = 1;

Plugin methods

The plugin provides a PrefixLayer object, which has the following methods and properties:


A kaleidoscope::plugin::PrefixLayer::Entry array that maps layers to prefix keys. The Entry constructor accepts Entry(layer_number, prefix_key). This array must be stored in PROGMEM as shown above.

Defaults to an empty array.


Length of the prefix_layers array.

Defaults to 0

Further reading

Starting from the example is the recommended way of getting started with the plugin.