YAML

YAML (short for YAML Ain’t Markup Language) is a human-readable data serialization standard commonly used for configuration files and data exchange. It originated as a replacement for XML and JSON in contexts where readability by humans is important. The YAML 1.2 specification is the current standard, and YAML is designed to be a superset of JSON, with JSON documents being valid YAML documents.

YAML uses indentation to denote structure. It represents data as scalars (strings, numbers, booleans, null), sequences (lists), and mappings (dictionaries). Basic syntax relies on indentation and the colon followed by a space to map keys to values; lists are introduced by a dash and a space. YAML also supports flow notation with braces and brackets for inline mappings and sequences. In addition, it provides anchors and aliases using & and * to reuse nodes, and block scalars introduced by | or > for multi-line strings. Comments begin with #. Tabs are not allowed for indentation.

YAML is widely used in software configuration and deployment. It is the format of many configuration files and is used extensively in Kubernetes manifests, Docker Compose files, and Ansible playbooks. Because YAML is a data-interchange format rather than a programming language, it is supported by libraries in most programming languages.

Cautions: YAML parsing can be sensitive to indentation and syntax, and loading YAML from untrusted sources can incur security risks in some libraries. Many ecosystems provide safe-loading options to avoid arbitrary code execution during parsing.