Docker vs Kubernetes: What They Are and How They Differ
Table of contents
Docker vs Kubernetes: what is each one? Docker is a tool for packaging applications into containers and running them on a single machine. Kubernetes is a system that manages many containers across many servers: it places them, scales them and brings them back after a failure. The two tools do not compete. Docker answers "how do I package and run an application", Kubernetes answers "how do I keep a hundred of them running". Below: both definitions, five differences, a diagram of how they work together and a guide to when Docker alone is enough.
Key takeaways: Docker builds images and runs containers, usually on one host. Kubernetes is an orchestrator: it manages containers across a cluster of machines. Google open-sourced Kubernetes in 2014, and today the Cloud Native Computing Foundation hosts the project. Since version 1.24 Kubernetes no longer uses Docker Engine to run containers, but images built with Docker run in it unchanged. A common setup uses both: Docker on the developer's machine and in CI, Kubernetes in production. For one application on one server, Docker with Compose is usually enough.
What is Docker?
Docker is an open platform for developing, shipping, and running applications, as the official documentation puts it. In practice it is about the container: an isolated process with its own file system, in which the application has everything it needs to run.
Three terms are enough to get started:
- Image: an immutable template with the application and its dependencies, built from a
Dockerfile. - Container: a running instance of an image.
- Registry: a store of images that a server or cluster pulls from.
Then there is Docker Compose, which describes several related containers in one file, for example an application, a database and a queue. Docker solves the "works on my machine" problem: the same image runs the same way on a laptop, in CI and on a server.
What is Kubernetes?
Kubernetes (K8s for short) is an open source container orchestration engine for automating deployment, scaling, and management of containerized applications. That is how the project documentation defines it. Orchestration here means deciding which container runs on which machine and making sure it stays that way.
Kubernetes works declaratively. You describe the desired state, for example "three copies of this application, reachable under one address", and the cluster works towards it. When a container dies, it starts a new one. When traffic grows, it can add copies. When you deploy a new version, it replaces containers gradually and lets you roll back to the previous one.
As of 5 November 2026, the newest release branch is 1.37, and the project maintains the three most recent minor releases (release list).
Docker vs Kubernetes: the differences at a glance
- Job. Docker: build an image and run a container. Kubernetes: manage many containers in a cluster.
- Scale. Docker: one machine. Kubernetes: many machines (nodes) treated as one pool of resources.
- Failure. Docker: restarts the container on the same host; if the host goes down, the application is down. Kubernetes: moves containers to healthy nodes.
- Configuration. Docker: a
Dockerfileand a Compose file. Kubernetes: YAML manifests describing the desired state. - Learning curve. Docker: a handful of commands. Kubernetes: a separate body of knowledge covering networking, permissions, storage and cluster upgrades.
Docker packages the application. Kubernetes keeps it running once machines and containers multiply.
How do Docker and Kubernetes work together?
Most often both tools sit in one chain. A developer builds an image with Docker and pushes it to a registry, and Kubernetes pulls the image and runs it in pods, the smallest units a cluster manages.
An illustrative example of the same image in both tools:
docker build -t registry.example.com/shop-api:1.0 .
docker run -d -p 8080:8080 registry.example.com/shop-api:1.0
docker push registry.example.com/shop-api:1.0
kubectl create deployment shop-api --image=registry.example.com/shop-api:1.0 --replicas=3
kubectl expose deployment shop-api --port=80 --target-port=8080Does Kubernetes still use Docker?
Not for running containers. The intermediate layer called dockershim was removed in Kubernetes 1.24, as described in the official FAQ. A cluster uses runtimes that implement the CRI standard, such as containerd. Nothing changes for developers: an image from docker build follows the OCI standard and runs in any of them.
When is Docker enough, and when do you need Kubernetes?
Docker alone (with Compose) is usually enough when:
- the application runs on one server and a short break during deployment is acceptable,
- traffic is predictable and there is no need to add copies automatically,
- nobody on the team has time to maintain a cluster.
Kubernetes starts to pay off when:
- there are a dozen or more services deployed by different teams,
- the application has to survive the failure of a single machine,
- traffic swings widely and automatic scaling is needed,
- deployments have to happen without downtime, with a quick way to roll back.
There is also a middle path. Docker Engine has a built-in Swarm mode, a simpler cluster operated with the same docker command. And Kubernetes can be bought as a managed service from a cloud provider, which takes control plane maintenance off the team.
Kubernetes has its price: more components to configure, monitor and upgrade. For a small project that cost can outweigh the benefit, so a sensible order is containers first and a cluster only once you have a problem it solves.
Summary
"Docker or Kubernetes" is rarely a choice of one of the two. Docker is the starting point, because without a container image Kubernetes has nothing to run. Scale decides about the cluster: the number of services, the availability you need and how much traffic varies.
Wondering whether your application needs Kubernetes or a simpler infrastructure will do? Contact Midapt and book a free consultation.
FAQ
Docker is a tool for building images and running containers, while Kubernetes is a system that manages containers across many servers. The first packages the application, the second handles its deployment, scaling and resilience to failures.
No. Kubernetes does not build images, it only runs ready ones. Images are still most often built with Docker, and Kubernetes takes over at the deployment stage.
Yes. A single application or a few related containers can run with Docker and Docker Compose alone. Kubernetes becomes necessary only with many services, many servers or a high availability requirement.
Formally no, but in practice it helps a lot. The concepts of image, container and registry are shared, so learning usually starts with Docker.
Kubernetes. Docker basics are a few commands and one file, while Kubernetes requires understanding clusters, networking, permissions and how to describe state in manifests.
Yes. Images built with Docker follow the OCI standard, so the runtimes Kubernetes uses, including containerd, can run them. The change in version 1.24 affected cluster administrators, not the way images are built.
