Peter's keyboard firmware (QMK)
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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:

Key Aliases Description
KC_MS_UP KC_MS_U Move cursor up
KC_MS_DOWN KC_MS_D Move cursor down
KC_MS_LEFT KC_MS_L Move cursor left
KC_MS_RIGHT KC_MS_R Move cursor right
KC_MS_BTN1 KC_BTN1 Press button 1
KC_MS_BTN2 KC_BTN2 Press button 2
KC_MS_BTN3 KC_BTN3 Press button 3
KC_MS_BTN4 KC_BTN4 Press button 4
KC_MS_BTN5 KC_BTN5 Press button 5
KC_MS_WH_UP KC_WH_U Move wheel up
KC_MS_WH_DOWN KC_WH_D Move wheel down
KC_MS_WH_LEFT KC_WH_L Move wheel left
KC_MS_WH_RIGHT KC_WH_R Move wheel right
KC_MS_ACCEL0 KC_ACL0 Set speed to 0
KC_MS_ACCEL1 KC_ACL1 Set speed to 1
KC_MS_ACCEL2 KC_ACL2 Set speed to 2

Configuring mouse keys

Mouse keys supports two different modes to move the cursor:

  • Accelerated (default): Holding movement keys accelerates the cursor until it reaches its maximum speed.
  • Constant: Holding movement keys moves the cursor at constant speeds.

The same principle applies to scrolling.

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:

Define Default Description
MOUSEKEY_DELAY 300 Delay between pressing a movement key and cursor movement
MOUSEKEY_INTERVAL 50 Time between cursor movements
MOUSEKEY_MAX_SPEED 10 Maximum cursor speed at which acceleration stops
MOUSEKEY_TIME_TO_MAX 20 Time until maximum cursor speed is reached
MOUSEKEY_WHEEL_MAX_SPEED 8 Maximum number of scroll steps per scroll action
MOUSEKEY_WHEEL_TIME_TO_MAX 40 Time 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.

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

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:

Define Default Description
MK_3_SPEED Not defined Enable constant cursor speeds
MK_MOMENTARY_ACCEL Not defined Enable momentary speed selection
MK_C_OFFSET_UNMOD 16 Cursor offset per movement (unmodified)
MK_C_INTERVAL_UNMOD 16 Time between cursor movements (unmodified)
MK_C_OFFSET_0 1 Cursor offset per movement (KC_ACL0)
MK_C_INTERVAL_0 32 Time between cursor movements (KC_ACL0)
MK_C_OFFSET_1 4 Cursor offset per movement (KC_ACL1)
MK_C_INTERVAL_1 16 Time between cursor movements (KC_ACL1)
MK_C_OFFSET_2 32 Cursor offset per movement (KC_ACL2)
MK_C_INTERVAL_2 16 Time between cursor movements (KC_ACL2)
MK_W_OFFSET_UNMOD 1 Scroll steps per scroll action (unmodified)
MK_W_INTERVAL_UNMOD 40 Time between scroll steps (unmodified)
MK_W_OFFSET_0 1 Scroll steps per scroll action (KC_ACL0)
MK_W_INTERVAL_0 360 Time between scroll steps (KC_ACL0)
MK_W_OFFSET_1 1 Scroll steps per scroll action (KC_ACL1)
MK_W_INTERVAL_1 120 Time between scroll steps (KC_ACL1)
MK_W_OFFSET_2 1 Scroll steps per scroll action (KC_ACL2)
MK_W_INTERVAL_2 20 Time between scroll steps (KC_ACL2)