JSON vs XML: Which Format Should You Use?
JSON and XML both describe structured data as text, and both are still widely deployed. The right choice depends on whether you need a lightweight data payload or a document format with validation, namespaces and mixed content. Here is the honest comparison.
The same data, side by side
<order id="A-9931">
<total currency="EUR">249.90</total>
<items>
<item sku="TS-01" qty="2"/>
<item sku="TS-04" qty="1"/>
</items>
</order>{
"id": "A-9931",
"total": { "currency": "EUR", "amount": 249.90 },
"items": [
{ "sku": "TS-01", "qty": 2 },
{ "sku": "TS-04", "qty": 1 }
]
}Notice what XML gives you that JSON does not: attributes, a namespace mechanism and a natural way to mix text and markup. Notice what JSON gives you that XML does not: real arrays, real numbers and booleans, and roughly a third less text for the same payload.
Feature comparison
| Aspect | JSON | XML |
|---|---|---|
| Payload size | Compact — no closing tags | Larger, typically 30–50% more bytes |
| Data types | String, number, boolean, null, object, array | Everything is text until a schema says otherwise |
| Arrays | First-class | Repeated elements by convention |
| Comments | Not supported | Supported |
| Attributes / metadata | Must be modelled as fields | Native attributes |
| Schema validation | JSON Schema (optional, widely used) | XSD / DTD / RELAX NG (mature) |
| Query language | JSONPath, jq | XPath, XQuery (very powerful) |
| Namespaces | None | Built in |
| Browser support | JSON.parse is native and fast | DOMParser, more verbose |
| Mixed content | Awkward | Designed for it |
When JSON is the right choice
- Web and mobile APIs, where payload size and parse speed matter
- Configuration consumed by JavaScript or Node tooling
- Structured logs and event streams
- Anything a browser reads directly — JSON.parse is dramatically faster than DOM parsing
When XML still wins
- Document formats where text and markup interleave (DOCX, SVG, XHTML, DocBook)
- Enterprise and government interchange with a mandated XSD contract
- SOAP services, SAML assertions and other standards that specify XML
- Pipelines that rely on XSLT transformations or complex XPath queries
- Feeds such as RSS, Atom and XML sitemaps
Size differences shrink once gzip or brotli compression is applied — repeated XML tags compress extremely well. Choose on structure and tooling, not on raw byte count alone.
Converting between them
XML to JSON is lossy by nature: attributes, namespaces, comments, processing instructions and element order all have to be encoded into conventions such as "@attr" and "#text". JSON to XML is easier but produces verbose output. If both systems must interoperate long term, define one canonical format and treat the other as a rendering of it.
{
"total": {
"@currency": "EUR",
"#text": "249.90"
}
}Common mistakes
Migrating for its own sake
Replacing a working, schema-validated XML integration with JSON rarely pays for itself. Migrate when you gain something concrete.
Ignoring validation after switching
Teams often drop XSD and add nothing in its place. Adopt JSON Schema so contracts stay enforceable.
Modelling XML thinking in JSON
Single-element arrays that collapse into objects break consumers. Keep arrays as arrays, even with one item.
JSON Formatter
Inspect either payload: format JSON, convert it to XML, CSV or YAML, and compare structures.
Frequently asked questions
Is JSON replacing XML?
For web APIs, largely yes. For document formats, publishing and regulated enterprise interchange, XML remains the standard.
Which is faster to parse?
JSON, in practice. Browsers implement JSON.parse in native code, while XML requires building a full DOM tree.
Can JSON have attributes like XML?
Not natively. Metadata has to become an ordinary field, which is why XML-to-JSON conversion needs naming conventions.
Does XML have a JSON Schema equivalent?
Yes — XSD predates JSON Schema and is more expressive, particularly for ordering and mixed content rules.
Put this into practice
JSON Formatter runs entirely in your browser — no upload, no account, no limits.
Open JSON FormatterRelated tools
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