Virtual machines and containers are both tools frequently used by developers to develop, test, and deploy software. On paper, they share many similarities: both run within a host operating system, allowing multiple applications to operate on the same hardware. They’re transferable between systems, provide isolation between applications and hosts, and can be easily set up. However, they’re really designed for totally different purposes. Here are a few ways containers and virtual machines differ.

Containers vs. virtual machines at a glance

Containers Virtual machines
Description A package containing all the dependencies to run a single application in isolation. Fully virtualized, isolated computers, including all of its hardware and software.
Managed by Container engines Hypervisors
Use cases Deploy applications in cloud-native environments, quickly scale service capacity, improve application portability. Running Legacy applications, consolidating servers, developing software on an isolated operating system environment.
Notable examples Docker, Amazon ECS, Red Hat Openshift. VMWare Fusion, Oracle VirtualBox, Microsoft Hyper-V.

5 Containers can’t run full operating systems

Containers are designed for single applications

Hypervisors like Hyper-V let you run fully-fledged operating systems on a single host.

Virtual machines run on top of a hypervisor, which in turn runs on the host operating system. They are great for any situation requiring multiple operating systems on the same machine. With them, you can run any number of Linux distributions or Windows versions concurrently, provided you have the hardware to power them all.

Virtual machines are excellent for running OS-specific programs, such as proprietary software or legacy applications. They’re also ideal for situations requiring stronger isolation and security.

Containers, on the other hand, run on a container engine over the host operating system, but they are designed to run only a specific application. Container installation packages, called images, include only the application and its required files. All containers share the same host operating system.

4 Containers are leaner

Containers use less resource

Docker is the big name in container solutions.

Because containers do not run operating systems, they are much leaner and consume fewer resources than virtual machines. This makes them ideal for running multiple containers simultaneously, as developer teams often do.

Setting up and sharing containers is also easy. Once an application has been packaged into a container image, you can easily move it between machines or share it on a platform like GitHub. Docker, a popular container platform, has its Docker Registry container distributor built into its desktop client.

3 Containers are quicker to set up

Containers are faster to spin up and shut down

If you have an image file ready, you can fire up a container in seconds. The Docker Registry (above) also lets you download pre-packaged images from its library.

To set up an application within a virtual machine, you’ll need to allocate its resources, install the operating system, and set up all the files the application needs. Conversely, setting up a container’s pre-packaged image file takes just a couple of clicks or commands.

A container’s speedy installation time makes it useful in many situations. For example, in cloud applications that need scalability, a load balancer can instantly spin up container instances to handle an unexpected workload spike or shut them down on demand to save resources.

2 Virtual machines have greater isolation

Virtual machines are better for security

Virtual machines (and their hypervisors) virtualize the entire hardware stack, including processors, memory, storage, and even network adapters. Since they run their own operating system, they also encapsulate their own kernel and software stack. This setup creates a strong isolation between the host operating system and between virtual machines.

Containers also provide isolation between each other, but since they share all hardware resources and run on a single host operating system, their isolation is less robust.

To get the best of both worlds, containers are often run inside virtual machines.

1 Virtual machines are more complex

They can be easily customized for specific needs

You can customize the virtualized hardware resources for a VM.

Since they virtualize both hardware and software, virtual machines are suitable for complex setups. Within them, you can create a completely separate development environment or workspace, something containers aren't designed for. Unlike virtual machines, most container applications are managed via commands rather than a graphical interface. While graphical interfaces are supported, they are not commonly used, as those who work with containers are typically seasoned developers.

Containers and virtual machines are similar in concept but are worlds apart

There are many ways virtual machines and containers are used in development, but their similarities can be a little confusing. In a nutshell, containers are isolated instances of applications, while virtual machines are virtualized full computers. The former is quick to deploy, while the latter is better suited for complex tasks. Neither replaces the other; they are often used in tandem in cloud applications, servers and database management, and software development.