What is Hypervisor?
A hypervisor is a software layer that creates and runs virtual machines by abstracting and isolating physical hardware resources for multiple operating systems.
A hypervisor, also called a virtual machine monitor (VMM), is a software layer that sits between the physical hardware and the operating systems running on top of it. Its primary job is to partition the host machine's resources, such as CPU, memory, and storage, and allocate them to one or more isolated virtual machines (VMs). Each VM runs its own guest operating system, unaware that it is sharing hardware with other VMs.
Hypervisors fall into two types. Type 1 (bare-metal) hypervisors run directly on the host hardware without an underlying operating system. Examples include VMware ESXi, Microsoft Hyper-V, and KVM (which is part of the Linux kernel). Type 2 (hosted) hypervisors run as a software application on top of an existing operating system. Examples include Oracle VirtualBox and VMware Workstation. Type 1 hypervisors are the standard in data centers and cloud infrastructure because they offer lower overhead, higher performance, and better security isolation.
In the wider hosting stack, the hypervisor is the foundation of virtualization. It enables cloud providers to run dozens or hundreds of VMs on a single physical server, dramatically improving hardware utilization and reducing costs. The hypervisor also enforces resource limits and handles VM migration, snapshots, and live backups. Without the hypervisor, modern Infrastructure as a Service (IaaS) platforms such as AWS EC2 and Google Compute Engine would not exist.
Key facts
- Hypervisors abstract physical hardware to run multiple guest operating systems concurrently.
- Type 1 (bare-metal) hypervisors run directly on hardware; Type 2 run on a host OS.
- Common Type 1 hypervisors include VMware ESXi, Microsoft Hyper-V, and KVM.
- Hypervisors enforce resource isolation and security boundaries between VMs.
- They enable live migration, snapshots, and high availability in production data centers.
How it works in practice
Related terms
References
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