# Docker Compose

URL: https://softwaredictionary.org/terms/docker-compose
Category: DevOps & Cloud
Last updated: 2026-10-03
Pronunciation: DOK-er kum-POHZ

In short: Docker Compose is a tool for defining and running multi-container applications, such as a web server plus a database, from one YAML file with one command.

## What is Docker Compose?

A real application rarely runs in one container. A typical setup needs the app itself, a PostgreSQL database, a Redis cache and perhaps a background worker, each with ports, environment variables and storage. Compose describes all of them in a `compose.yaml` file, and `docker compose up` starts the whole stack, with the containers able to reach each other by service name on a shared network.

Each service names an image to pull or a folder to build, and can declare ports, environment variables, volumes for data that should survive restarts, health checks and dependencies on other services. `docker compose down` stops and removes everything, `logs` shows the combined output, and `exec` opens a shell in a running service.

Compose is mostly used for local development and testing: a new developer clones the repository, runs one command and has the same database versions and settings as everyone else. It is also used for small single-server deployments and in CI pipelines to start the dependencies that integration tests need.

A common misconception is that Compose replaces Kubernetes. Compose runs containers on one machine and has no built-in scheduling across a cluster, self-healing or rolling updates across nodes. For production systems that span many servers, an orchestrator such as Kubernetes, or a managed container service, is the usual choice.

## Key takeaways

- Docker Compose runs multi-container applications from one YAML file.
- docker compose up starts every service on a shared network.
- Services declare images, ports, environment variables, volumes and health checks.
- It is ideal for local development, testing and small single-server setups.
- It runs on one machine; Kubernetes orchestrates clusters.

## Example: A compose.yaml for an app with a database and a cache

```yaml
services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      DATABASE_URL: postgres://app:secret@db:5432/app   # "db" is the service name
      REDIS_URL: redis://cache:6379
    depends_on:
      db:
        condition: service_healthy

  db:
    image: postgres:17
    environment:
      POSTGRES_USER: app
      POSTGRES_PASSWORD: secret
    volumes:
      - db-data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD", "pg_isready", "-U", "app"]

  cache:
    image: redis:8

volumes:
  db-data:

# docker compose up -d     start everything in the background
# docker compose down      stop and remove the containers
```

## Frequently asked questions

**What is the difference between Docker and Docker Compose?**

Docker builds and runs individual containers. Docker Compose sits on top and runs a group of containers that make up one application, defined together in a YAML file.

**Should I use Docker Compose in production?**

For small apps on a single server it can work well. For systems that need several servers, automatic failover or zero-downtime rolling updates, Kubernetes or a managed container platform is a better fit.

**What is the difference between docker-compose and docker compose?**

docker-compose with a hyphen is the original standalone tool. docker compose with a space is the newer version built into the Docker command line as a plugin, which is the one to use today. Both read the same file format.

---

Software Dictionary: https://softwaredictionary.org/ · https://softwaredictionary.org/llms.txt