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Mouse keys

Mouse keys is a feature that allows you to emulate a mouse using your keyboard. You can move the pointer at different speeds, press 5 buttons and scroll in 8 directions.

Adding mouse keys to your keyboard

To use mouse keys, you must at least enable mouse keys support and map mouse actions to keys on your keyboard.

Enabling mouse keys

To enable mouse keys, add the following line to your keymap’s


Mapping mouse actions

In your keymap you can use the following keycodes to map key presses to mouse actions:

KC_MS_UPKC_MS_UMove cursor up
KC_MS_DOWNKC_MS_DMove cursor down
KC_MS_LEFTKC_MS_LMove cursor left
KC_MS_RIGHTKC_MS_RMove cursor right
KC_MS_BTN1KC_BTN1Press button 1
KC_MS_BTN2KC_BTN2Press button 2
KC_MS_BTN3KC_BTN3Press button 3
KC_MS_BTN4KC_BTN4Press button 4
KC_MS_BTN5KC_BTN5Press button 5
KC_MS_BTN6KC_BTN6Press button 6
KC_MS_BTN7KC_BTN7Press button 7
KC_MS_BTN8KC_BTN8Press button 8
KC_MS_WH_UPKC_WH_UMove wheel up
KC_MS_WH_DOWNKC_WH_DMove wheel down
KC_MS_WH_LEFTKC_WH_LMove wheel left
KC_MS_WH_RIGHTKC_WH_RMove wheel right
KC_MS_ACCEL0KC_ACL0Set speed to 0
KC_MS_ACCEL1KC_ACL1Set speed to 1
KC_MS_ACCEL2KC_ACL2Set speed to 2

Configuring mouse keys

Mouse keys supports three different modes to move the cursor:

  • Accelerated (default): Holding movement keys accelerates the cursor until it reaches its maximum speed.
  • Kinetic: Holding movement keys accelerates the cursor with its speed following a quadratic curve until it reaches its maximum speed.
  • Constant: Holding movement keys moves the cursor at constant speeds.
  • Combined: Holding movement keys accelerates the cursor until it reaches its maximum speed, but holding acceleration and movement keys simultaneously moves the cursor at constant speeds.
  • Inertia: Cursor accelerates when key held, and decelerates after key release. Tracks X and Y velocity separately for more nuanced movements. Applies to cursor only, not scrolling.

The same principle applies to scrolling, in most modes.

Configuration options that are times, intervals or delays are given in milliseconds. Scroll speed is given as multiples of the default scroll step. For example, a scroll speed of 8 means that each scroll action covers 8 times the length of the default scroll step as defined by your operating system or application.

Accelerated mode

This is the default mode. You can adjust the cursor and scrolling acceleration using the following settings in your keymap’s config.h file:

MOUSEKEY_DELAY10Delay between pressing a movement key and cursor movement
MOUSEKEY_INTERVAL20Time between cursor movements in milliseconds
MOUSEKEY_MAX_SPEED10Maximum cursor speed at which acceleration stops
MOUSEKEY_TIME_TO_MAX30Time until maximum cursor speed is reached
MOUSEKEY_WHEEL_DELAY10Delay between pressing a wheel key and wheel movement
MOUSEKEY_WHEEL_INTERVAL80Time between wheel movements
MOUSEKEY_WHEEL_DELTA1Wheel movement step size
MOUSEKEY_WHEEL_MAX_SPEED8Maximum number of scroll steps per scroll action
MOUSEKEY_WHEEL_TIME_TO_MAX40Time until maximum scroll speed is reached


  • Setting MOUSEKEY_DELAY too low makes the cursor unresponsive. Setting it too high makes small movements difficult.
  • For smoother cursor movements, lower the value of MOUSEKEY_INTERVAL. If the refresh rate of your display is 60Hz, you could set it to 16 (1/60). As this raises the cursor speed significantly, you may want to lower MOUSEKEY_MAX_SPEED.
  • Setting MOUSEKEY_TIME_TO_MAX or MOUSEKEY_WHEEL_TIME_TO_MAX to 0 will disable acceleration for the cursor or scrolling respectively. This way you can make one of them constant while keeping the other accelerated, which is not possible in constant speed mode.
  • Setting MOUSEKEY_WHEEL_INTERVAL too low will make scrolling too fast. Setting it too high will make scrolling too slow when the wheel key is held down.

Cursor acceleration uses the same algorithm as the X Window System MouseKeysAccel feature. You can read more about it on Wikipedia.

Kinetic Mode

This is an extension of the accelerated mode. The kinetic mode uses a quadratic curve on the cursor speed which allows precise movements at the beginning and allows to cover large distances by increasing cursor speed quickly thereafter. You can adjust the cursor and scrolling acceleration using the following settings in your keymap’s config.h file:

MK_KINETIC_SPEEDundefinedEnable kinetic mode
MOUSEKEY_DELAY5Delay between pressing a movement key and cursor movement
MOUSEKEY_INTERVAL10Time between cursor movements in milliseconds
MOUSEKEY_MOVE_DELTA16Step size for accelerating from initial to base speed
MOUSEKEY_INITIAL_SPEED100Initial speed of the cursor in pixel per second
MOUSEKEY_BASE_SPEED5000Maximum cursor speed at which acceleration stops
MOUSEKEY_DECELERATED_SPEED400Decelerated cursor speed
MOUSEKEY_ACCELERATED_SPEED3000Accelerated cursor speed
MOUSEKEY_WHEEL_INITIAL_MOVEMENTS16Initial number of movements of the mouse wheel
MOUSEKEY_WHEEL_BASE_MOVEMENTS32Maximum number of movements at which acceleration stops


  • The smoothness of the cursor movement depends on the MOUSEKEY_INTERVAL setting. The shorter the interval is set the smoother the movement will be. Setting the value too low makes the cursor unresponsive. Lower settings are possible if the micro processor is fast enough. For example: At an interval of 8 milliseconds, 125 movements per second will be initiated. With a base speed of 1000 each movement will move the cursor by 8 pixels.
  • Mouse wheel movements are implemented differently from cursor movements. While it's okay for the cursor to move multiple pixels at once for the mouse wheel this would lead to jerky movements. Instead, the mouse wheel operates at step size 1. Setting mouse wheel speed is done by adjusting the number of wheel movements per second.

Constant mode

In this mode you can define multiple different speeds for both the cursor and the mouse wheel. There is no acceleration. KC_ACL0, KC_ACL1 and KC_ACL2 change the cursor and scroll speed to their respective setting.

You can choose whether speed selection is momentary or tap-to-select:

  • Momentary: The chosen speed is only active while you hold the respective key. When the key is raised, mouse keys returns to the unmodified speed.
  • Tap-to-select: The chosen speed is activated when you press the respective key and remains active even after the key has been raised. The default speed is that of KC_ACL1. There is no unmodified speed.

The default speeds from slowest to fastest are as follows:

  • Momentary: KC_ACL0 < KC_ACL1 < unmodified < KC_ACL2
  • Tap-to-select: KC_ACL0 < KC_ACL1 < KC_ACL2

To use constant speed mode, you must at least define MK_3_SPEED in your keymap’s config.h file:

#define MK_3_SPEED

To enable momentary mode, also define MK_MOMENTARY_ACCEL:


Use the following settings if you want to adjust cursor movement or scrolling:

MK_3_SPEEDNot definedEnable constant cursor speeds
MK_MOMENTARY_ACCELNot definedEnable momentary speed selection
MK_C_OFFSET_UNMOD16Cursor offset per movement (unmodified)
MK_C_INTERVAL_UNMOD16Time between cursor movements (unmodified)
MK_C_OFFSET_01Cursor offset per movement (KC_ACL0)
MK_C_INTERVAL_032Time between cursor movements (KC_ACL0)
MK_C_OFFSET_14Cursor offset per movement (KC_ACL1)
MK_C_INTERVAL_116Time between cursor movements (KC_ACL1)
MK_C_OFFSET_232Cursor offset per movement (KC_ACL2)
MK_C_INTERVAL_216Time between cursor movements (KC_ACL2)
MK_W_OFFSET_UNMOD1Scroll steps per scroll action (unmodified)
MK_W_INTERVAL_UNMOD40Time between scroll steps (unmodified)
MK_W_OFFSET_01Scroll steps per scroll action (KC_ACL0)
MK_W_INTERVAL_0360Time between scroll steps (KC_ACL0)
MK_W_OFFSET_11Scroll steps per scroll action (KC_ACL1)
MK_W_INTERVAL_1120Time between scroll steps (KC_ACL1)
MK_W_OFFSET_21Scroll steps per scroll action (KC_ACL2)
MK_W_INTERVAL_220Time between scroll steps (KC_ACL2)

Combined mode

This mode functions like Accelerated mode, however, you can hold KC_ACL0, KC_ACL1 and KC_ACL2 to momentarily (while held) set the cursor and scroll speeds to constant speeds. When no acceleration keys are held, this mode is identical to Accelerated mode, and can be modified using all of the relevant settings.

  • KC_ACL0: This acceleration sets your cursor to the slowest possible speed. This is useful for very small and detailed movements of the cursor.
  • KC_ACL1: This acceleration sets your cursor to half the maximum (user defined) speed.
  • KC_ACL2: This acceleration sets your cursor to the maximum (computer defined) speed. This is useful for moving the cursor large distances without much accuracy.

To use combined speed mode, you must at least define MK_COMBINED in your keymap’s config.h file:


Inertia mode

This mode provides smooth motion, like sliding on ice. The cursor accelerates along a quadratic curve while a key is held, then glides to a stop after the key is released. Vertical and horizontal movements are tracked independently, so the cursor can move in many directions and make curves.

Cannot be used at the same time as Kinetic mode, Constant mode, or Combined mode.

Recommended settings in your keymap’s config.h file:

MOUSEKEY_INERTIAundefinedEnable Inertia mode
MOUSEKEY_DELAY150Delay between pressing a movement key and cursor movement
MOUSEKEY_INTERVAL16Time between cursor movements in milliseconds (16 = 60fps)
MOUSEKEY_MAX_SPEED32Maximum cursor speed at which acceleration stops
MOUSEKEY_TIME_TO_MAX32Number of frames until maximum cursor speed is reached
MOUSEKEY_FRICTION24How quickly the cursor stops after releasing a key
MOUSEKEY_MOVE_DELTA1How much to move on first frame (1 strongly recommended)


  • Set MOUSEKEY_DELAY to roughly the same value as your host computer's key repeat delay, in ms. Recommended values are 100 to 300.
  • Set MOUSEKEY_INTERVAL to a value of 1000 / your monitor's FPS. For 60 FPS, 1000/60 = 16.
  • Set MOUSEKEY_MAX_SPEED based on your screen resolution and refresh rate, like Width / FPS. For example, 1920 pixels / 60 FPS = 32 pixels per frame.
  • Set MOUSEKEY_TIME_TO_MAX to a value of approximately FPS / 2, to make it reach full speed in half a second (or so).
  • Set MOUSEKEY_FRICTION to something between 1 and 255. Lower makes the cursor glide longer. Values from 8 to 40 are the most effective.
  • Keep MOUSEKEY_MOVE_DELTA at 1. This allows precise movements before the gliding effect starts.
  • Mouse wheel options are the same as the default accelerated mode, and do not use inertia.

Use with PS/2 Mouse and Pointing Device

Mouse keys button state is shared with PS/2 mouse and pointing device so mouse keys button presses can be used for clicks and drags.