JSON, YAML and TOML: compare the same configuration

Start with the format required by the consuming application. If it expects JSON, a more readable YAML file is not a compatible replacement until the pipeline explicitly converts and validates it.

The same configuration in three formats

Download config.json, then try JSON to YAML and JSON to TOML. These versions describe the same nested data:

{"name":"api-gateway","port":8080,"featureFlags":["rate-limit","audit-log"],"database":{"host":"localhost","poolSize":20}}

name: api-gateway
port: 8080
featureFlags:
  - rate-limit
  - audit-log
database:
  host: localhost
  poolSize: 20

name = "api-gateway"
port = 8080
featureFlags = ["rate-limit", "audit-log"]

[database]
host = "localhost"
poolSize = 20

In TOML, featureFlags belongs before [database]. Keys written after that header belong to the database table until another table header changes the context. Moving that array below the header would produce database.featureFlags, changing the configuration even though parsing succeeds.

Convert back with YAML to JSON or TOML to JSON. Check port is a number, featureFlags is at the root, and database.poolSize is 20. Formatting and key order may differ without changing these values.

Differences that affect a round trip

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The JSONCraft converter warns about some unsupported TOML values, including nulls and root arrays. A warning is a reason to inspect the data contract, not proof that the replacement is equivalent.

A practical choice

Choose JSON for interchange when broad support and a strict data model matter. Choose YAML when the surrounding toolchain uses it and human annotations or its additional syntax are useful. Choose TOML for configuration that fits its tables and explicit scalar types. Human-edited JSON remains sensible when the application requires it and editors provide validation.

YAML behavior depends on version and parser options. YAML 1.1 may interpret NO as false; YAML 1.2 narrowed boolean spelling. Tags and merge-key support also vary. Do not assume that a browser conversion proves another runtime’s loader has identical semantics. Use a safe loader for untrusted YAML and validate the result.

TOML arrays permit trailing commas; JSON does not. TOML inline tables have their own rules, so state which TOML version your parser supports instead of treating all punctuation rules as interchangeable.

Keep secrets out of examples and feedback forms. The converter processes input locally, while hosting and optional measurement follow the privacy policy.

References: JSON RFC 8259, YAML 1.2.2 specification, and TOML 1.0 specification.