ESXi

ESXi is VMware's bare-metal hypervisor — the software that runs directly on server hardware and makes virtualization possible. It's the foundation layer of every VMware vSphere deployment: each physical host runs ESXi, which then hosts the virtual machines on top of it.

A hypervisor sits between the physical hardware and the VMs. ESXi exposes CPU, memory, storage, and network resources to virtual machines, giving each VM the appearance of dedicated hardware while actually sharing the physical resources efficiently across many workloads.

In a managed VMware environment, ESXi hosts are controlled through vCenter — you don't typically interact with each host directly. ESXi becomes relevant operationally when you're dealing with host-level issues: hardware failures, firmware updates, network configuration, or storage connectivity problems.

Notable change: the free ESXi license was discontinued by Broadcom in 2024. Organizations running free ESXi — common in smaller environments and branch offices — need to evaluate licensed alternatives or migrate to another platform.