YAML vs JSON: What's the Difference and Which Should You Use?

YAML vs JSON at a glance

The same data in both formats

YAML:

project: ToolZone
features:
  - formatter
  - converter
enabled: true

JSON:

{
  "project": "ToolZone",
  "features": ["formatter", "converter"],
  "enabled": true
}

Both examples represent a mapping with a string, an array, and a boolean. JSON punctuation is more explicit; YAML depends more heavily on indentation and scalar interpretation.

Choose JSON for predictable interchange

JSON is a strong default for browser APIs, service payloads, logs consumed by many tools, and data that will rarely be edited by hand. Its standard data model includes objects, arrays, strings, numbers, booleans, and null. Standard JSON does not allow comments or trailing commas.

Choose YAML for human-maintained configuration

YAML can be easier to scan when configuration contains long nested structures, repeated blocks, or comments. It also supports features that have no direct JSON equivalent, including comments, anchors and aliases, explicit tags, and multi-document streams. Those features can be helpful but also increase parser and conversion complexity.

Parsing and security considerations

Never parse YAML by splitting lines or guessing indentation. Use a maintained parser, limit aliases and resource consumption where supported, and avoid unsafe construction of language-specific objects from untrusted input. Validate the resulting data against the schema your application expects.

JSON also requires validation. Syntactically valid input can still contain unexpected fields, duplicate-name behavior, oversized numbers, or values of the wrong type.

Will conversion lose information?

Converting YAML to JSON can discard comments, anchors, aliases, tags, document boundaries, formatting choices, and some type information. The data values may remain useful while the original authoring context is lost. Keep the YAML source when comments or YAML-specific features matter.

Frequently asked questions

Is every JSON file valid YAML?

YAML 1.2 was designed so JSON syntax fits within YAML, but actual compatibility can depend on parser version, duplicate-key handling, numeric behavior, and application constraints. Test with the exact parser in use.

Does JSON support comments?

Standard JSON defined by RFC 8259 does not include comments. Some tools accept JSON-like extensions, but those files are not portable standard JSON. Keep documentation outside the payload or use a format whose comment rules are defined.

Which format is faster to parse?

Performance varies by library, document, and environment. JSON's smaller grammar often enables efficient built-in implementations, but choose based on measured workloads and interoperability rather than assuming syntax alone determines application speed.