One-shots are a new kind of behaviour for your standard modifier and momentary layer keys: instead of having to hold them while pressing other keys, they can be tapped and released, and will remain active until any other key is pressed subject to a time-out.

In short, they turn Shift, A into Shift+A, and Fn, 1 to Fn+1. The main advantage is that this allows us to place the modifiers and layer keys to positions that would otherwise be awkward when chording. Nevertheless, they still act as normal when held, that behaviour is not lost.

Furthermore, if a one-shot key is double-tapped ie tapped two times in quick succession, it becomes sticky, and remains active until disabled with a third tap. This can be useful when one needs to input a number of keys with the modifier or layer active, and does not wish to hold the key down. If this “stickability” feature is undesirable, it can be unset (and later again set) for individual modifiers/layers. If stickability is unset, double-tapping a one-shot modifier will just restart the timer.

To make multi-modifier, or multi-layer shortcuts possible, one-shot keys remain active if another one-shot of the same type is tapped, so Ctrl, Alt, b becomes Ctrl+Alt+b, and L1, L2, c is turned into L1+L2+c. Furthermore, modifiers and other layer keys do not cancel the one-shot effect, either.

Using One-Shot keys

To enter one-shot mode, tap quickly on a one-shot key. The next normal (non-one-shot) key you press will have the modifier applied, and then the modifier will automatically turn off. If the Shift key is a one-shot modifier, then hitting Shift, a, b will give you Ab, if you hit shift quickly.

Longish keypresses do not activate one-shot mode. If you press Shift, a, b, as above, but hold the Shift key a bit longer, you’ll get ab.

To enter sticky mode, tap twice quickly on a one-shot key. The modifier will now stay on until you press it again. Continuing the Shift example, tapping Shift, Shift quickly and then a, b, c, Shift, d, e, f will give you ABCdef.

This can be a bit tricky; combining this plugin with LED-ActiveModColor will help you understand what state your one-shot is in; when a one-shot key is active, it will have a yellow LED highlight; when sticky, a red highlight. When it is in a “held” state, but will be deactivated when released like any non-one-shot key, it will have a white highlight. (These colors are configurable.)

Using the plugin

After adding one-shot keys to the keymap, all one needs to do, is enable the plugin:

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

// somewhere in the keymap...
OSM(LeftControl), OSL(_FN)


void setup() {

Keymap markup

There are two macros the plugin provides:


A macro that takes a single argument, the name of the modifier: LeftControl, LeftShift, LeftAlt, LeftGui or their right-side variant. When marked up with this macro, the modifier will act as a one-shot modifier.


Takes a layer number as argument, and sets up the key to act as a one-shot layer key.

Please note that while Kaleidoscope supports more, one-shot layers are limited to 8 layers only.

In addition, there is a special key:


A key that behaves like a one-shot key, but while active, it makes other keys that are pressed become sticky, just like double-tapped one-shot keys.

Plugin methods

The plugin provides one object, OneShot, which implements both one-shot modifiers and one-shot layer keys. It has the following methods:

Configuration methods: Timeouts


OneShot keys will remain active after they’re pressed for timeout milliseconds (or until a subsequent non-oneshot key is pressed). The default value is 2500 (2.5 seconds).


If a one-shot key is held for longer than timeout milliseconds, it will behave like a normal key, and won’t remain active after it is released. The default value is 250 (1/4 seconds).


If a one-shot key is double-tapped (pressed twice in a row) in less than timeout milliseconds, it wil become sticky, and will remain active until it is pressed a third time. The default value is -1, which indicates that it should use the same timeout as .setTimeout().

Configuration methods: Stickability



Enables/disables stickability for all keys listed. The keys should all be OneShot keys, modifier keys, or layer-shift keys, as specified on the keymap. For example: OneShot.enableStickability(OSM(LeftShift), OSL(1), Key_RightGUI). OneShot.disableStickability(OSM(RighttAlt), OSL(2), ShiftToLayer(4)).

By default, all OneShot keys are stickable.





Enables/disables stickability for all modifiers and layers, respectively. These are convenience methods for cases where one wants to enable stickability for a group of one-shot keys.

Configuration methods: Automatic one-shot keys




Enables/disables/toggles auto-oneshot functionality for modifier keys. When enabled, all normal modifier keys, including those with other modifier flags added to them (e.g. LSHIFT(Key_LeftAlt), Key_Meh) will be automatically treated as one-shot keys, in addition to dedicated ones like OSM(LeftGui).




Enables/disables/toggles auto-oneshot functionality for layer shift keys (see above).




Enables/disables/toggles auto-oneshot functionality for all modifiers and layer shift keys.

Test methods


Returns true if the key at key_addr is in an active one-shot state. Note that if a key is still being held, but will be not remain active after it is released, it is not considered to be in a one-shot state, even if it had been earlier.


Returns true if the key at key_addr is in a temporary one-shot state. Such a key will eventually time out or get deactivated by a subsequent key press.


Returns true if the key at key_addr is in a permanent one-shot state. Such a key will not be deactivated by subsequent keypresses, nor will it time out. It will only be deactivated by pressing it one more time, or by being cancelled by the cancel() method (see below).


Returns true if there are any active one-shot keys. Note: it returns false if there are no currently active one-shot keys, but there are keys that were at one time in a one-shot state, but are still being held after that state has been cancelled.


Returns true if there are any sticky one-shot keys.


Returns true if a key of the specified value can be made sticky by double-tapping.


Returns true if the specified key is a modifier key. This does not include OneShot modifiers (e.g. OSM(LeftShift)), but it does include modifiers with additional modifier flags (e.g. Key_Meh, LCTRL(Key_RightGui)).


Returns true if the specified key is a layer-shift key (e.g. ShiftToLayer(2)). OneShot layer keys (e.g. OSL(5) are not included).


Returns true if the specified key is a OneShot modifier or layer-shift key (e.g. OSM(LeftAlt), OSL(3)).

Other methods


Immediately deactivates the one-shot status of any temporary one-shot keys. Any keys still being physically held will continue to function as normal modifier/layer-shift keys.

If with_stickies is true (the default is false), sticky one-shot keys will also be deactivated, in the same way.

Deprecated methods

The following methods have been deprecated, and should no longer be used, if possible. These functions made more sense when OneShot was based on Key values; it has since be rewritten to be based on KeyAddr values.

.inject(key, key_state)

Finds an idle key on the keyboard, and turns it into a one-shot key. When OneShot was based on Key values, this made more sense, as it didn’t need a valid KeyAddr to work. Since the main purpose of this method was to enable the triggering of multiple one-shot modifiers with a single key, it is much better to use automatic one-shot modifiers, if possible, because then it’s not necessary to use a Macro to configure.


Returns true if a keymap cache entry with the current value of key is active (one-shot, sticky, or held). This should be a function that is not specific to OneShot.


Returns true if a keymap cache entry with the current value of key is in an active one-shot state. Please use .isActive(key_addr) instead.


Returns true if a keymap cache entry with the current value of key is in a sticky one-shot state. Please use .isSticky(key_addr) instead.


Returns false. OneShot doesn’t need to keep track of whether or not a one-shot key is still pressed any more. This function was mainly used by LED-ActiveModColor, which no longer needs it.


Further reading

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