What file format does Docker Compose use to define the services?

Docker Compose uses YAML (YAML Ain't Markup Language) as its file format to define the services that make up an application. YAML is favored for its readability and simplicity, allowing developers to write configuration files in a way that is easy for humans to read and understand. The structure of a YAML file is based on indentation, which helps visually represent the hierarchy and relationships between different services, networks, and volumes in a Docker application.

Using YAML within Docker Compose makes it convenient to define multiple services, each with their configurations such as images, environment variables, ports, and networks. This allows for a clean and organized way to manage complex multi-container applications, and contributes to Docker Compose's role in facilitating rapid application development and deployment.

The other formats mentioned – JSON, XML, and TXT – are not used by Docker Compose for this purpose. JSON can be quite verbose compared to YAML, and while XML is also structured, it tends to be more complex and harder to read. TXT is not structured and wouldn't effectively represent the complexities of service definitions.