compose

Docker Compose is an official Docker tool that lets you define and run multi-container applications with a single configuration file and a single command. The problem it solves is coordination: a real-world application often needs several pieces running together — for example, a web server, a database, and a caching service. Without Compose, you would have to start each container manually in the right order with the right settings. Compose lets you describe all of those pieces in one YAML file called compose.yaml and then bring everything up at once with "docker compose up."

The configuration file specifies each service in your application, which Docker image to use, which ports to open, which files to mount from your computer, and how the services connect to each other. When you run the up command, Compose reads that file, creates the containers with the right configuration, and links them together on a private network so they can communicate. You can tear down the whole stack just as easily with a single command.

You would use Docker Compose when developing locally and needing to spin up a realistic environment that mirrors production — for example, a Python web app alongside a PostgreSQL database and a Redis cache. It is also commonly used in CI/CD pipelines to run integration tests against a real database. On Windows and macOS, Compose comes bundled with Docker Desktop so no separate installation is needed. On Linux, it is downloaded as a plugin binary. The tool is written in Go and is maintained as an open-source project by Docker.