File with a .VMX extension contains settings of a virtual device, such as memory limits, used within disc space or the processor usage, stored in a form of plain text. This format enables to define the properties with the value_name = value_properties syntax, for instance, maximal memory available for the virtual device = “1024”, that is – 1024 MB.

The VMX configuration files are utilised by the VMware virtualisation software. In the VMware Fusion version, a configuration file can be stored also with the CFG extension, for virtual devices created in older software versions.