XML vs JSON: When to Use Each and How to Convert Between Them
Compare XML and JSON across use cases, tooling, and data modeling capabilities. Learn when each format is the better choice and how to convert between them without losing information.
Key Takeaways
- JSON and XML model data differently at a conceptual level.
- XML excels when document structure matters: HTML/XHTML, SVG, SOAP web services, office document formats (OOXML, ODF), and any content with mixed text and markup.
- JSON dominates for data interchange: REST APIs, configuration files, NoSQL databases, and browser-to-server communication.
- XML attributes, namespaces, mixed content, and element ordering have no direct JSON equivalents.
- Always verify the output structure after conversion.
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Fundamental Differences
JSON and XML model data differently at a conceptual level. JSON uses a data-centric model — arrays, objects, and primitives. XML uses a document-centric model — elements, attributes, and mixed content (text interspersed with markup). This distinction means some data converts cleanly while other structures lose information in translation.
Feature Comparison
| Feature | JSON | XML |
|---|---|---|
| Data types | 6 (string, number, boolean, null, array, object) | Strings (with schema typing) |
| Comments | No | Yes |
| Attributes | No concept | Yes |
| Mixed content | No | Yes (text + elements) |
| Namespaces | No | Yes |
| Schema validation | JSON Schema | XSD, DTD, RelaxNG |
| XPath/XSLT queries | No (use JSONPath) | Yes (mature tooling) |
| File size | Smaller (typically 30-50%) | Larger (verbose tags) |
When XML Wins
XML excels when document structure matters: HTML/XHTML, SVG, SOAP web services, office document formats (OOXML, ODF), and any content with mixed text and markup. XML namespaces enable combining vocabularies without conflicts.
When JSON Wins
JSON dominates for data interchange: REST APIs, configuration files, NoSQL databases, and browser-to-server communication. Its native mapping to JavaScript objects and Python dicts makes it the natural choice for web applications.
Conversion Pitfalls
XML attributes, namespaces, mixed content, and element ordering have no direct JSON equivalents. Different converters handle these differently, producing incompatible JSON structures. Always verify the output structure after conversion. Convert between XML and JSON with the Peasy format converter.