SendInput function (winuser.h)

Synthesizes keystrokes, mouse motions, and button clicks.


UINT SendInput(
  [in] UINT    cInputs,
  [in] LPINPUT pInputs,
  [in] int     cbSize


[in] cInputs

Type: UINT

The number of structures in the pInputs array.

[in] pInputs


An array of INPUT structures. Each structure represents an event to be inserted into the keyboard or mouse input stream.

[in] cbSize

Type: int

The size, in bytes, of an INPUT structure. If cbSize is not the size of an INPUT structure, the function fails.

Return value

Type: UINT

The function returns the number of events that it successfully inserted into the keyboard or mouse input stream. If the function returns zero, the input was already blocked by another thread. To get extended error information, call GetLastError.

This function fails when it is blocked by UIPI. Note that neither GetLastError nor the return value will indicate the failure was caused by UIPI blocking.


This function is subject to UIPI. Applications are permitted to inject input only into applications that are at an equal or lesser integrity level.

The SendInput function inserts the events in the INPUT structures serially into the keyboard or mouse input stream. These events are not interspersed with other keyboard or mouse input events inserted either by the user (with the keyboard or mouse) or by calls to keybd_event, mouse_event, or other calls to SendInput.

This function does not reset the keyboard's current state. Any keys that are already pressed when the function is called might interfere with the events that this function generates. To avoid this problem, check the keyboard's state with the GetAsyncKeyState function and correct as necessary.

Because the touch keyboard uses the surrogate macros defined in winnls.h to send input to the system, a listener on the keyboard event hook must decode input originating from the touch keyboard. For more information, see Surrogates and Supplementary Characters.

An accessibility application can use SendInput to inject keystrokes corresponding to application launch shortcut keys that are handled by the shell. This functionality is not guaranteed to work for other types of applications.


// Sends Win + D to toggle to the desktop
void ShowDesktop()
    OutputString(L"Sending 'Win-D'\r\n");
    INPUT inputs[4] = {};
    ZeroMemory(inputs, sizeof(inputs));

    inputs[0].type = INPUT_KEYBOARD;
    inputs[0].ki.wVk = VK_LWIN;
    inputs[1].type = INPUT_KEYBOARD;
    inputs[1].ki.wVk = VK_D;

    inputs[2].type = INPUT_KEYBOARD;
    inputs[2].ki.wVk = VK_D;
    inputs[2].ki.dwFlags = KEYEVENTF_KEYUP;

    inputs[3].type = INPUT_KEYBOARD;
    inputs[3].ki.wVk = VK_LWIN;
    inputs[3].ki.dwFlags = KEYEVENTF_KEYUP;

    UINT uSent = SendInput(ARRAYSIZE(inputs), inputs, sizeof(INPUT));
    if (uSent != ARRAYSIZE(inputs))
        OutputString(L"SendInput failed: 0x%x\n", HRESULT_FROM_WIN32(GetLastError()));


Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header winuser.h (include Windows.h)
Library User32.lib
DLL User32.dll

See also




Keyboard Input


Surrogates and Supplementary Characters