What is a valid format for a Docker Compose file?

A Docker Compose file is used to define and run multi-container Docker applications. The most commonly accepted format for these files is YAML (YAML Ain't Markup Language), which is both human-readable and easy to write. YAML allows users to define services, networks, and volumes in a structured manner, making it well-suited for the configuration of complex applications that require multiple interacting Docker containers.

Using YAML provides clear indentation and structure, which enhances readability and organization of the configurations, making it easier for developers and operators to understand the services and their interactions. It supports comments and is versatile, which further contributes to its popularity in various applications beyond just Docker Compose.

Other formats like .txt, .json, or .html do not align with the standard practices for Docker Compose files. Plain text files lack the structured format necessary for configuration, while JSON can be more cumbersome to write due to its strict syntax and lack of comments. HTML, mainly used for web pages, is entirely inappropriate for defining configurations for container orchestration. Hence, YAML stands out as the valid and preferred format for Docker Compose files.