JSON and YAML both describe trees of maps, sequences, and scalars, but they make different trade-offs. JSON is a small, strict grammar designed for interchange; YAML is a larger configuration language designed for human editing.
01Where they differ
JSON and YAML compared
Aspect
JSON
YAML
Grammar
Strict and small (RFC 8259 / ECMA-404)
Larger, with anchors, aliases, tags, and multiple documents
Types
Object, array, string, number, boolean, null
Same core scalars plus explicit tags and dates
Whitespace
Insignificant
Indentation is structure
Comments
Not allowed
Allowed
Typical use
Interchange between systems
Configuration read and edited by people
02Converting safely
JSON to YAML round-trips the same value model, including integers larger than JavaScript can represent exactly, as long as the converter preserves scalar literals and does not add anchors or tags. The reverse is not lossless for every YAML feature: anchors, aliases, tags, and complex keys have no JSON representation.