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A hypervisor is software that lets one physical server run multiple independent operating systems at once — the foundation virtually all modern cloud computing, server consolidation, and virtual desktop infrastructure is built on.
Normally, a single computer runs one operating system that has direct control over the hardware — the processor, memory, storage, and network. A hypervisor changes that by inserting itself as a management layer between the physical hardware and the operating systems running on top of it.
Instead of one OS owning the whole machine, the hypervisor divides the underlying hardware resources — CPU, RAM, storage, networking — among several independent virtual machines (VMs), each of which behaves as though it has its own dedicated computer. When a VM needs a hardware resource, it requests it through the hypervisor, which arbitrates between all the VMs running on the host to prevent them from interfering with one another.
This is the technology underpinning server consolidation, cloud computing platforms, virtual desktop infrastructure (VDI), and modern DevOps workflows that spin up and tear down environments on demand.
Hypervisors fall into two categories, and the distinction matters for anyone specifying infrastructure.
Runs directly on the physical server hardware, with no underlying operating system in between. Because there's no OS layer to go through, Type 1 hypervisors deliver lower latency, better resource utilisation, and a smaller attack surface than Type 2.
Examples: VMware ESXi, Microsoft Hyper-V (in server deployment), Citrix Hypervisor, Xen.
Typical use: Enterprise data centres, cloud infrastructure providers, and any environment hosting large numbers of production VMs.
Runs as an application on top of an existing operating system (Windows, macOS, or Linux), rather than directly on hardware. This makes it simpler to install and use, but adds a layer of overhead the host OS introduces.
Examples: VMware Workstation, Oracle VM VirtualBox, Parallels Desktop.
Typical use: Development, testing, training environments, and personal use where convenience matters more than maximum performance.
For production enterprise environments, Type 1 hypervisors are almost always the right choice — the performance, scalability, and security advantages of running directly on hardware outweigh the convenience of a hosted model. Type 2 hypervisors remain genuinely useful, but for development, testing, and situations where a full dedicated host isn't justified — not for production workloads.
The choice of hypervisor also shapes decisions further up the stack: licensing costs, compatibility with existing backup and disaster recovery tooling, integration with your storage platform, and the skills your team already has all factor into which platform makes sense.
Run many virtual servers on far less physical hardware, cutting capital cost, power, cooling, and rack space.
Provision new environments in minutes rather than procuring and racking new physical servers.
A properly configured hypervisor keeps VMs isolated from one another, containing the impact of a compromised workload.
Virtual machines can be backed up, replicated, and restored far more easily than physical servers.
There's no single "best" hypervisor — the right choice depends on scale, existing infrastructure, and workload requirements. Considerations typically include:
Specifying a virtualisation platform for a new deployment or refresh? Talk to us about the right hypervisor and underlying server/storage infrastructure for your environment.
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