A practical comparison of JSON and XML — syntax, use cases, performance, and when each format is the right choice for APIs, config files, and data exchange.
Use JSON for REST APIs, configuration files, and data that maps naturally to objects and arrays.
Use XML for document-centric content, legacy enterprise systems, SOAP APIs, and when you need mixed content (text with inline markup like or ).
In practice, if you're building something new today, you'll almost certainly use JSON.
The same data in both formats:
JSON:
``json
{
"user": {
"name": "Alice",
"age": 30,
"roles": ["admin", "editor"]
}
}
`
XML:
`xml
`
JSON is visibly more concise for this type of structured data.
REST APIs: JSON is the standard. Tools like Swagger/OpenAPI, Postman, and every major HTTP client library have first-class JSON support.
JavaScript environments: JSON maps directly to JavaScript objects — no parsing library needed, just JSON.parse().
Configuration files: Most modern tools use JSON or YAML for config (package.json, tsconfig.json).
File size: JSON is typically 30–40% smaller than equivalent XML because it has less markup overhead.
Document-centric content: XML handles mixed content naturally — text with inline formatting tags like or `. HTML is itself a form of XML.
Legacy enterprise integration: SOAP web services, EDI (Electronic Data Interchange), and older financial systems speak XML. The financial industry (FIX protocol, ISO 20022) is heavily XML-based.
Strong validation requirements: XML Schema (XSD) and Schematron provide powerful document validation. While JSON Schema exists, it's less mature.
RSS and Atom feeds: Both formats are XML-based and remain widely used for content syndication.
Office documents: DOCX, XLSX, and PPTX are ZIP archives containing XML files.
If you need to work with both formats, our converters handle the transformation:
- XML to JSON → — Convert XML API responses or data exports to JSON
- JSON to XML → — Convert JSON data to XML for legacy systems
Use our JSON Formatter to validate and beautify JSON, and the XML Formatter to do the same for XML.
|---|---|
Not always. XML is better for document-centric data, mixed content (text with inline markup), and cases where document validation via schemas (XSD) is required. JSON is better for data-centric APIs and configuration.
JSON is generally faster to parse than XML because it has a simpler grammar and maps directly to native data structures in most languages.
Standard JSON does not support comments. Use JSONC (JSON with Comments) for configuration files, or switch to YAML if human-authored configuration needs comments.
JSON is the de facto standard for REST APIs. It is lighter, easier to parse in JavaScript, and better supported by API tooling like Swagger/OpenAPI.