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A hypervisor is a software package which provides virtual machines.

There are two main types of hypervisors, classified by their level of abstraction from the physical hardware:

  • Type 1 - 'native' hypervisors, which are operating systems which run directly on the bare machine
  • Type 2 - 'hosted' hypervisors, which are applications which run under a general-purpose OS.

The Type 2 hypervisors, for example VMware Workstation or Oracle VirtualBox, run as an application within the host operating system, ex: as a Linux or Windows program. To minimize overhead, Type 1 hypervisors avoid the need for the host to run another operating system, and they instead run directly on the bare-metal hardware. Examples of Type 1 hypervisors include VMware ESXi, Microsoft Hyper-V, and KVM.


Early hypervisors were created by IBM, including CP/CPS and VM/370, which allowed for creating VMs of different operating systems on the mainframe.