JSON vs YAML vs XML: choosing the right format

JSON, YAML and XML all describe structured data, but they make very different trade-offs. Picking the right one is less about taste and more about who — or what — reads the file next.

JSON: the machine's favorite

JSON is strict and predictable: quoted keys, no comments, and a grammar that every language parses identically. That strictness is why APIs default to it. If a file is produced and consumed by machines, JSON is usually right.

YAML: built for humans

YAML replaces braces with indentation, which makes configs like CI pipelines pleasant to read and edit. The price is silent failures: a misplaced space changes meaning, and values like no or 0777 can parse as booleans or octal numbers. YAML rewards careful editors and punishes copy-paste.

XML: documents and contracts

XML is verbose but expressive — attributes, mixed content, namespaces and schema validation make it strong where documents must be validated against a contract (SOAP, DOCX internals, SVG, enterprise feeds).

A quick rule of thumb

• Machines talking to machines → JSON
• Humans editing by hand → YAML
• Document structure or strict schemas → XML

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