YAML

programming

Stands for: YAML Ain't Markup Language

A human-readable data format often used for configuration.

YAML Ain't Markup Language is a whitespace-based serialization format popular for config files and CI pipelines. Its readability comes with sharp edges, like type-coercion surprises and significant indentation.

YAML is what configuration became when people decided JSON was too noisy to write by hand. It is a superset of JSON, so anything valid in one is valid in the other, and it adds comments, references, multi-line strings and indentation-based structure that make large configuration files genuinely readable.

The cost is that whitespace is syntax. A single misplaced space changes structure rather than raising an obvious error, and the failure often appears far from the edit, as a key nested one level deeper than intended. Tabs are forbidden entirely, which surprises people whose editor helpfully inserts them.

The famous trap is type inference. Unquoted values get interpreted, so a country code, a version number, or a value that merely looks boolean can silently become something else, and older parsers treated a whole family of words as booleans. Quoting anything that must stay a string is the habit that prevents the class of bug where a configuration file is valid, parses cleanly, and means something other than what it says.

Also known as: yaml

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