JSON vs XML vs YAML vs TOML: When to Use Each

The Formats at a Glance

Feature	JSON	XML	YAML	TOML
Human readable	Yes	Moderate	Yes	Yes
Comments	No	Yes	Yes	Yes
Schema support	Yes	Yes	Partial	No
Browser native	Yes	Yes	No	No

Best for: REST APIs, web apps, data interchange.

JSON is the default for HTTP APIs. Every language has a native parser, it's compact, and browsers understand it natively.

{ "host": "localhost", "port": 5432 }

Best for: Enterprise systems, SOAP APIs, document formats (SVG, RSS).

<config>
  <host>localhost</host>
  <port>5432</port>
</config>

Best for: Config files (Docker Compose, Kubernetes, CI/CD).

host: localhost
port: 5432

Best for: Application config (Rust's Cargo.toml, Python's pyproject.toml).

[database]
host = "localhost"
port = 5432

Feature	JSON	XML	YAML	TOML
Human readable	Yes	Moderate	Yes	Yes
Comments	No	Yes	Yes	Yes
Schema support	Yes	Yes	Partial	No
Browser native	Yes	Yes	No	No

Best for: REST APIs, web apps, data interchange.

JSON is the default for HTTP APIs. Every language has a native parser, it's compact, and browsers understand it natively.

{ "host": "localhost", "port": 5432 }

Best for: Enterprise systems, SOAP APIs, document formats (SVG, RSS).

<config>
  <host>localhost</host>
  <port>5432</port>
</config>

Best for: Config files (Docker Compose, Kubernetes, CI/CD).

host: localhost
port: 5432

Best for: Application config (Rust's Cargo.toml, Python's pyproject.toml).

[database]
host = "localhost"
port = 5432