VMware ESXi

VMware’s bare-metal hypervisor (called ESX again since VCF 9), whose own kernel runs VMs directly on servers while vCenter adds vMotion, HA, DRS and vSAN; since Broadcom bought VMware in 2023 it is sold only as per-core subscriptions.

What it is: Hypervisors
Used for: Virtual machines
Type: Commercial product
Made by: Broadcom (VMware)
License: Proprietary
Facts checked: 11 October 2026

What it is

ESXi installs straight onto a server, with no general-purpose operating system underneath. Broadcom’s security guide says it is not built on the Linux kernel or a Linux distribution: it uses VMware’s own kernel, the VMkernel, and its own tools. ESXi 8.0 needs at least two CPU cores with Intel VT-x or AMD RVI turned on, 8 GB of RAM and a 32 GB boot disk, and the server should be on VMware’s compatibility guide. A VM is a folder of files on a datastore: its configuration (.vmx), its virtual disks and its logs. Datastores on block storage use VMFS, a cluster file system: many ESXi hosts can open the same datastore at once, and on-disk locking stops two hosts from running the same VM. NFS, vSAN and vVols datastores work too. Inside each guest, VMware Tools adds drivers, time sync and quiesced snapshots; most Linux distributions ship the open-source open-vm-tools.

One host can be run from its web Host Client, but the features people buy vSphere for come from vCenter Server, the central administrator for many hosts. vMotion moves a running VM to another host without interruption, Storage vMotion moves its disks between datastores, vSphere HA restarts a failed host’s VMs on other hosts in the cluster, DRS spreads load across hosts, and Fault Tolerance keeps a live secondary copy of a VM. vSAN is built into the ESXi kernel and pools the hosts’ local disks into one shared datastore. Broadcom ships all of this inside VMware Cloud Foundation (VCF) and the smaller vSphere Foundation. With VCF 9.0 (June 17, 2025) the hypervisor was renamed back to ESX; the current release is ESX 9.1.1 (September 3, 2026), the 8.0 line still gets updates (8.0 Update 3k, July 2026), and 7.x reached end of general support on October 2, 2025.

Broadcom completed its purchase of VMware on November 22, 2023. On December 11, 2023 it ended sales of perpetual licenses and of support renewals for them: VMware products are now subscriptions or term licenses, counted per physical core with a minimum of 16 cores per CPU. In February 2024 Broadcom discontinued the free ESXi hypervisor, marking it end of general availability “along with the termination of perpetual licensing”. A free license came back with ESXi 8.0 Update 3e (an April 2025 release), limited to two physical CPUs per host and 8 vCPUs per VM, with no vCenter, vMotion, HA or DRS, read-only APIs and no support.

Why teams pick it

A full cluster feature set from one vCenter: live migration of VMs and their disks, automatic restarts after a host failure, load balancing, fault tolerance and in-kernel vSAN storage
A purpose-built kernel instead of a general-purpose OS, and VMFS, which lets every host in a cluster share the same block storage safely
A large ecosystem built on one API: govc, PowerCLI, a Broadcom-maintained Terraform provider and Packer plugin, backup tools, and hardware certified in the compatibility guide
Guests are well supported: VMware Tools for Windows, and open-vm-tools already packaged by most Linux distributions

Watch out for

Since December 2023 there are no perpetual licenses: only subscriptions, priced per core with a 16-core minimum per CPU and sold mainly as the VCF or vSphere Foundation bundles
The free edition vanished from February 2024 until April 2025, and today’s free license can’t join vCenter, has no vMotion, HA or DRS, allows only read-only API use and has no support
Closed source and tied to certified hardware: ESXi 8.0 needs at least 2 cores, 8 GB of RAM and a 32 GB boot disk, and support follows Broadcom’s lifecycle (7.x ended in October 2025)
Leaving takes work, though rivals now help: Proxmox VE 8.2 (April 2024) added a wizard that imports VMs straight from ESXi 6.5 to 8.0

Alternatives

What all hypervisors have in common →

Cloud HypervisorOpen sourceA Rust virtual machine monitor for modern cloud VMs on KVM or Microsoft’s hypervisor: virtio devices only, plus hotplug, VFIO passthrough, live migration, snapshots and Windows guests.KVM (Kernel-based Virtual Machine)Open sourceThe hypervisor built into the Linux kernel: it runs guest code directly on the CPU through `/dev/kvm`, and leaves device emulation to a user-space program such as QEMU or Firecracker.

libvirtOpen sourceA stable API, daemon and `virsh` command line for managing virtual machines, storage and networks, with drivers for QEMU/KVM, Xen, LXC, Cloud Hypervisor, VMware ESX, Hyper-V and more.

Microsoft Hyper-VCommercialMicrosoft’s type-1 hypervisor, built into Windows Server and Windows 10 and 11 Pro and Enterprise: a thin hypervisor under a Windows root partition, which also underpins Azure’s hypervisor and Windows features like VBS, WSL 2 and Windows Sandbox.

Oracle VirtualBoxOpen sourceOracle’s free, open-source desktop hypervisor: a type-2 hypervisor that runs VMs as an application on Windows, macOS, Linux and Solaris, scriptable with `VBoxManage` and the default provider for Vagrant.

Proxmox Virtual EnvironmentOpen sourceA Debian-based server platform from Vienna that runs KVM virtual machines and LXC containers, with clustering, high availability, Ceph and ZFS storage, backups and a web interface in one free ISO.

QEMUOpen sourceThe open-source machine emulator and virtualizer: it emulates whole computers in software, or runs them at native speed on a hypervisor such as KVM, and supplies the virtual devices either way.

Xen Project hypervisorOpen sourceThe open-source type-1 hypervisor from Cambridge that ran the first Amazon EC2 instances: a small microkernel-style core that boots first, with drivers and management in a privileged VM called dom0.

How it fits with other technologies

What VMware ESXi uses

What uses VMware ESXi

libvirtmanages VMs remotely via the vSphere API onVMware ESXiHypervisors

Drive vSphere from the command line with `govc` (run against `vcsim`, VMware’s vCenter API simulator, so no real ESXi is involved) · bash

# vcsim simulates vCenter with one standalone ESXi host and a 3-host cluster
docker run -d --rm --name vcsim -p 127.0.0.1:8989:8989 vmware/vcsim -l 0.0.0.0:8989
export GOVC_URL=https://user:pass@127.0.0.1:8989/sdk GOVC_INSECURE=1

govc about
# FullName:     VMware vCenter Server 6.5.0 build-5973321 (govmomi simulator)
# API type:     VirtualCenter
govc find / -type h                 # the ESXi hosts
# /DC0/host/DC0_H0/DC0_H0
# /DC0/host/DC0_C0/DC0_C0_H0
# /DC0/host/DC0_C0/DC0_C0_H1
# /DC0/host/DC0_C0/DC0_C0_H2

govc cluster.change -drs-enabled -drs-mode fullyAutomated -ha-enabled /DC0/host/DC0_C0

govc vm.create -c 2 -m 4096 -g ubuntu64Guest -net "VM Network" -ds LocalDS_0 \
  -pool /DC0/host/DC0_C0/Resources -host /DC0/host/DC0_C0/DC0_C0_H0 -on=false web01
govc vm.power -on web01
# Powering on VirtualMachine:vm-75... OK
govc datastore.ls -ds LocalDS_0 web01   # a VM is a folder of files on a datastore
# vmware.log
# web01.nvram
# web01.vmx

govc vm.migrate -host /DC0/host/DC0_C0/DC0_C0_H1 web01   # vMotion while it runs
# migrating VirtualMachine:vm-75... OK
govc vm.info web01
#   Power state:  poweredOn
#   Host:         DC0_C0_H1

docker stop vcsim

What vCenter adds to a cluster of ESXi hosts#

The optional vCenter Server components in Broadcom’s vSphere 8.0 documentation, plus vSAN. None of them are available with the free ESXi license.

vMotion

live migration

Moves a running VM from one ESXi host to another without interrupting it.

Storage vMotion

live migration

Moves a running VM’s disks and configuration file from one datastore to another.

vSphere HA

availability

When a host fails, restarts the VMs that were running on it on other hosts in the cluster.

DRS

scheduling

Balances resource use and power consumption across the hosts and resource pools of a cluster.

Fault Tolerance

availability

Keeps a secondary VM running in step with the primary, for continuous availability.

vSAN

storage

Built into the ESXi kernel: pools the local disks of the cluster’s hosts into one shared datastore. Licensed per TiB of raw capacity.

How the licensing changed under Broadcom#

	What happened	Source
Nov 22, 2023	Broadcom completes its acquisition of VMware.	Broadcom press release
Dec 11, 2023	End of sale of perpetual licenses and of support renewals for them; products become subscriptions or term licenses, mainly the VCF and vSphere Foundation bundles.	Broadcom (Krish Prasad) post
From 2024	VCF and vSphere Foundation are licensed per physical core, at least 16 cores per CPU.	Broadcom KB 313548
Feb 2024	The free ESXi hypervisor is marked end of general availability and removed from the website.	VMware knowledge base article, as reported by The Register
Apr 2025	A free license returns for ESXi 8.0 Update 3e: 2 CPUs per host, 8 vCPUs per VM, no vCenter and no support.	Broadcom KB 399823

See it in a real stack

No architecture uses VMware ESXi yet. Drop it into the playground and wire it up yourself.Open playground →

Where it came from1998–2025

VMware was founded in 1998 in Palo Alto. Its ESX Server, first released in 2001, ran directly on Intel servers and partitioned each one into several isolated virtual servers, so companies could consolidate many lightly used machines onto fewer ones. Classic ESX booted a Linux-based service console that ran next to the VMkernel and handled management. EMC bought VMware, closing on January 9, 2004.

On September 10, 2007 VMware announced ESX Server 3i: a 32 MB hypervisor with no general-purpose operating system, designed to be built into servers from Dell, HP, IBM and others. On July 28, 2008 VMware made the stand-alone ESXi free, to get companies of every size started with virtualization. vSphere 4.1 (2010) was the last release with both ESX and ESXi, and from 5.0 in August 2011 only ESXi remained.

Dell, which owned 81% of VMware by then, spun it off on November 1, 2021, and Broadcom completed its purchase on November 22, 2023. Within weeks Broadcom ended perpetual licenses and folded most products into two bundles, and in February 2024 it withdrew the free hypervisor. VCF 9.0 in June 2025 renamed ESXi back to ESX, though without the old service console, and a free license for ESXi 8.0 Update 3e followed.

Why it’s built this way

Bare metal instead of a hosted product: ESX Server was built to consolidate data center servers, so it ran directly on the hardware with its own kernel rather than as an application on Windows or Linux.
Dropping the service console: ESX Server 3i fit in 32 MB, and VMware said that having no general-purpose OS freed it from the work of maintaining one. Management moved to a small local console and remote clients.
A cluster file system for VM storage: VMFS lets several hosts open the same datastore at once, with on-disk locks so only one runs a given VM, so any host in a cluster can take over a VM’s files.
Bundles and subscriptions only: Broadcom said customers and partners found VMware’s offers too complex, and that subscriptions were already the industry standard; it cut the lineup to VCF and vSphere Foundation.

Timeline

1998
VMware founded in Palo Alto
2001
ESX Server, VMware’s first bare-metal hypervisor, ships
2007
ESX Server 3i: a 32 MB hypervisor with no service console
2008
ESXi becomes free to download (July 28)
2011
ESXi 5.0: classic ESX is gone; ESXi only
2023
Broadcom completes the acquisition (Nov 22) and ends perpetual licenses (Dec 11)
2025
VCF 9.0 renames ESXi to ESX (June); a free ESXi 8.0 license returns

Sources24 · facts checked 11 October 2026

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