What is an anonymous volume and why can it be a problem?

An anonymous volume is created when you specify a container-side mount path with no source name (e.g., -v /data or a Dockerfile VOLUME instruction with no docker run mapping). Docker auto-generates a random name for it. Because it has no memorable name, these accumulate invisibly across container recreations and are easy to forget about, leading to silent disk usage growth until someone runs docker volume prune.