YAMLs

YAMLs refer to files or documents written in YAML, a human-readable data serialization language used for configuration and data exchange. YAML stands for YAML Ain't Markup Language and was designed in the early 2000s to be easy to read and write while expressing complex data structures. It is widely used for configuration files, data exchange, and software deployment manifests, and YAML 1.2 is the current commonly implemented standard. JSON is a strict subset of YAML, which means any valid JSON is also valid YAML.

YAMLs are indentation-based and rely on whitespace to denote structure. Mappings are written as key: value pairs, and sequences as lines starting with a dash. Comments begin with the hash symbol. Documents can be separated by three hyphens (---). YAML supports multi-line strings using | or > and offers anchors and aliases to reuse data fragments. Strings may be quoted or unquoted, with rules for escaping and special characters. YAML also supports various data types, including strings, numbers, booleans, nulls, and complex nested combinations of mappings and sequences.

Common data types in YAMLs include scalars (strings, numbers, booleans), sequences (lists), and mappings (dictionaries). YAML files typically use the extensions .yaml or .yml. They are used in many ecosystems, notably for configuration (for example, application settings and CI/CD pipelines) and for infrastructure as code with tools like Kubernetes manifests.

While YAMLs are powerful and readable, they can be sensitive to indentation and syntax, and loading untrusted YAML can pose security risks in some parsers. Validation against a schema is advised, and best practices include consistent indentation and cautious use of anchors.