An M3P file is a plugin installer file used by Mach3, a computer numerical control (CNC) program for Windows. It is used to place a .DLL file in the "Plugins" folder of the Mach3 installation directory, which adds additional functionality of the Mach3 application, such as allowing an Android device to control Mach3 or enabling a user to control a mill with an Xbox 360 controller.

M3P files are typically packaged in a .ZIP archive with a DLL file that bears the same name as the M3P file. The DLL file contains the actual plugin information, but the M3P file is recognized as the plugin by Mach3. NOTE: Mach3 is a program that allows you to control various types of equipment to perform cut, print, and drill jobs based on digital designs. The software controls the motion of motors on various types of equipment, such as mills, lasers, routers, and engravers.