YAML

• YAML — Wikipedia

• The Official YAML Web Site

• *.yml

YAML is a superset of JSON

JSON can be used as YAML, but:

• duplicated keys can't be used ("JSON's RFC4627 requires that mappings keys merely “SHOULD” be unique, while YAML insists they “MUST” be" — YAML Ain’t Markup Language (YAML™) Version 1.2)

• JSON must not use tabs as indentation ("yaml.scanner.ScannerError: while scanning for the next token found character '\t' that cannot start any token in "<unicode string>"") (some parsers support it)

YAML can therefore be viewed as a natural superset of JSON, offering improved human readability and a more complete information model. This is also the case in practice; every JSON file is also a valid YAML file. This makes it easy to migrate from JSON to YAML if/when the additional features are required.

— YAML Ain’t Markup Language (YAML™) Version 1.2

• YAML as a JSON superset and TAB characters - Stack Overflow

Entity bomb

• Billion laughs — Wikipedia