Map backup file created by Source SDK, an SDK used to modify games provided by Valve's Steam gaming service; contains a backup of a .VMF map file created by the Hammer Editor component of the Source SDK.

Hammer Editor automatically create a VMX file when a VMF map file is saved. Therefore, they can be used to revert a map back to the last save point.

Configuration file used by VMware virtualization software such as VMware Workstation and VMware Fusion; stores settings for a virtual machine created with the New Virtual Machine Wizard; includes the memory, hard disk, and processor limit settings; enables a virtual machine to be started in the software.

VMX files are saved in a plain text format and contain a list of settings in the form of property = value. For example, the setting for the memory limit may be memsize = "512", which means that 512MB of RAM is the maximum memory allowed for the virtual machine. VMX files saved for VMware Fusion are generally stored within a .VMWAREVM package. NOTE: If the virtual machine was created with an earlier Linux version of VMware Workstation, the configuration file may use the .CFG extension.