LockWorkStation function

Locks the workstation's display. Locking a workstation protects it from unauthorized use.


BOOL WINAPI LockWorkStation(void);


This function has no parameters.

Return value

If the function succeeds, the return value is nonzero. Because the function executes asynchronously, a nonzero return value indicates that the operation has been initiated. It does not indicate whether the workstation has been successfully locked.

If the function fails, the return value is zero. To get extended error information, call GetLastError.


The LockWorkStation function is callable only by processes running on the interactive desktop. In addition, the user must be logged on, and the workstation cannot already be locked.

Common reasons the workstation might not be locked even if the function succeeds include the following: no user is logged on, the workstation is already locked, the process is not running on the interactive desktop, or the request is denied by the Graphical Identification and Authentication (GINA) DLL.

This function has the same result as pressing Ctrl+Alt+Del and clicking Lock Workstation. To unlock the workstation, the user must log in. There is no function you can call to determine whether the workstation is locked. To receive notification when the user logs in, use the WTSRegisterSessionNotification function to receive WM_WTSSESSION_CHANGE messages. You can use session notifications to track the desktop state so you know whether it is possible to interact with the user.


For an example, see How to Lock the Workstation.


Minimum supported client

Windows XP [desktop apps only]

Minimum supported server

Windows Server 2003 [desktop apps only]


Winuser.h (include Windows.h)





See also

System Shutdown Functions



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