Which programming language is Docker written in?

Docker's engine is written in Go, not Python. The core components, dockerd, containerd, and runc, are all Go projects, and Go's lightweight goroutines are a big part of why Docker can manage many container processes at once without a heavy threading model. Containerd and runc were later donated to the Cloud Native Computing Foundation and now sit underneath other container runtimes too, including Kubernetes, which shows how much of the modern container ecosystem is built in Go rather than Python.

Where does the Python confusion come from?

The mix-up usually traces back to Docker Compose. The original Compose (V1) was a separate command-line tool built in Python, and for years it stood out as the one Python-based piece sitting next to an otherwise Go-based toolchain. Docker rewrote it from scratch as Compose V2, a Go-based CLI plugin invoked as `docker compose` instead of the old `docker-compose` binary, so the team could share code with the Docker CLI and the Moby project instead of maintaining a second language.

What changed when Compose moved to Go?

Folding Compose into a Go plugin meant Docker could ship a fix or a new CLI feature once instead of porting it into Python separately, and Compose V2 commands run noticeably faster than the old Python binary did. Compose V2 is now the default bundled with Docker Desktop and the Docker CLI, and the standalone Python version is no longer the recommended way to set up a new project.

Why this matters for hiring

Teams extending Docker itself, custom CLI plugins, containerd-based tooling, or anything talking directly to the Docker Engine API, are typically looking for Go engineers, not Python developers. Docker's plugin system and CLI extensions are also built around Go interfaces, so contributing at that layer means working in the same language as the platform itself. Python stays relevant for what runs inside a container, but it is not the language behind the platform that runs it.