Which file extension is commonly used for Docker Compose files?

Docker Compose files typically utilize the .yml file extension, which stands for YAML Ain't Markup Language. YAML is a human-readable data serialization format that is often used for configuration files. When defining services, networks, and volumes in a Docker environment, YAML's structure allows for a clear and organized hierarchical representation.

The use of .yml for Docker Compose files is widely accepted and aligns with the community’s conventions, making it easier for developers to recognize and work with these files. While there can be variations like .yaml, the .yml extension is preferred and more commonly observed in Docker Compose documentation and examples.

In contrast, the other file extensions mentioned serve different purposes. Files with a .docker extension are not standard and do not indicate a common usage in the Docker ecosystem. The .docker-compose extension is also not officially recognized, and while JSON is a valid format for configuration, Docker Compose specifically uses YAML due to its readability and simplicity for complex configurations.