YAML, a recursive acronym forYAML Ain’t Markup Language (formerlyYet Another Markup Language), is atext‐baseddata serialization language.As of version 1.2, it is a strict superset ofJSON, but is commonly considered to be easier for humans to read and maintain than the latter.YAML is particularly well‐suited for metadata which is intended to be managed by hand; for example, manyMarkdown‐basedstatic site generators allow YAML metadata to be included at the beginning of documents as “frontmatter”.YAML is also commonly used as a configuration language, for similar reasons.

Note that even though the YAML 1.2 specification was released in 2009, many implementations unfortunately still only support YAML 1.1.