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What is the difference between a container and a virtual machine?
Updated 2 min read8 differences
In short
A container packages an app with its dependencies and shares the host's kernel, while a virtual machine runs its own OS: stronger isolation, more resources.
Container
A container is a lightweight, isolated package that bundles an application with its dependencies and runs it on the host's shared operating system kernel.
Read the page on ContainerVirtual Machine
A virtual machine is a software-based computer that runs its own operating system on shared physical hardware, isolated from other machines on the same host.
Read the page on Virtual MachineContainer and Virtual Machine compared
| Aspect | Container | Virtual Machine |
|---|---|---|
| What is virtualized | The operating system: processes, files, network | The hardware: CPU, memory, disks, network cards |
| Operating system | Shares the host's kernel | Runs its own full guest OS |
| Image size | Megabytes to a few hundred megabytes | Usually several gigabytes |
| Startup time | Milliseconds to a few seconds | Seconds to minutes |
| Isolation | Process-level; weaker because the kernel is shared | Hardware-level; a strong boundary enforced by the hypervisor |
| Density | Dozens to hundreds per host | A handful to dozens per host |
| Managed by | A container runtime, often orchestrated by Kubernetes | A hypervisor, on bare metal or on a host OS |
| Best for | Microservices, CI jobs and portable app deployments | Different operating systems, legacy apps, strong tenant isolation |
The difference, explained
A container is an isolated process, or group of processes, that runs from an image containing the app and everything it needs, like libraries and configuration. A virtual machine (VM) is a complete emulated computer with virtual CPUs, memory, disks and its own guest operating system, managed by a hypervisor on the physical host.
The difference is the level of virtualization. VMs virtualize hardware, so each one boots a full OS kernel, takes gigabytes of disk and often needs tens of seconds to start. Containers virtualize the operating system: on Linux they use kernel features called namespaces and cgroups to isolate processes, so they share one kernel, usually start in under a second and pack densely onto one machine.
They are usually combined rather than chosen between. In the cloud, most containers actually run inside VMs, which provide the strong security boundary between customers while containers provide fast, portable packaging for apps. Lightweight micro-VMs blend the two, giving each container or function its own tiny VM for extra isolation.
A common misconception is that containers are just smaller VMs with the same isolation. Because containers share the host kernel, a kernel vulnerability can affect all of them, and a Linux container cannot run natively on a Windows or macOS kernel; container tools on those systems quietly run a Linux VM in the background.
Which one should you use?
Choose Container when…
- You want fast, repeatable deployments of many small services.
- Apps should run the same on a laptop, in CI and in production.
- You need to start and stop instances in seconds to scale.
Choose Virtual Machine when…
- You need a different operating system or kernel than the host.
- Workloads from untrusted tenants need strong isolation.
- You are running legacy software that expects a whole machine.
Readers ask
Are containers less secure than virtual machines?
Their isolation is weaker, because VMs each have their own kernel while containers share one. Containers can still be run securely with good practices, but a kernel flaw affects every container on the host.
Can you run containers inside a virtual machine?
Yes, and it is the most common setup in the cloud: VMs provide isolation between customers, and containers run inside them to package and scale applications.