Set wParam to 0xF170 (SC_MONITORPOWER).It's so easy to trigger the monitor to sleep using the Win32 API WM_SYSCOMMAND: Hmmm, seems Windows has never improved, because I recall having this requirement back-in-the-day - haha, that was during my first project ever, when I was involved in some Win32 development. I wanted to turn off my monitor in Windows 10, while listening to music, rather than wait for the Power plan “Turn off the display” timer to kick in.