YAML (YAML Ain't Markup Language) is a human-readable data serialization format that uses indentation to represent hierarchical structure. It is widely used for configuration files and data exchange.

YAML supports comments (#) and is designed as a superset of JSON. It has become the de facto standard for DevOps tool configuration files including Docker Compose, Kubernetes, GitHub Actions, and Ansible. DevOps introduction books cover YAML usage patterns extensively.

Notable YAML caveats include the prohibition of tab characters for indentation (spaces only) and implicit type conversion (e.g., yes being converted to a boolean). These specifications can cause unexpected bugs.

From a character count perspective, YAML uses fewer brackets and quotation marks, tending to require fewer characters than JSON for representing the same data. Infrastructure automation books provide additional context.