At a glance
| Aspect | JSON | XML |
|---|---|---|
| Syntax | Braces / brackets / colons | Nested tags |
| Size | Compact | Verbose |
| Data types | String, number, bool, null, array, object | All values are strings |
| Comments | Not allowed (JSON5 allows) | Yes |
| Schema | JSON Schema | XSD, DTD |
| Namespaces | No | Yes (xmlns) |
| Attributes | No (everything is a key) | Yes |
| Mixed content | Awkward | Natural |
| Transformations | Ad-hoc | XSLT, XPath |
| Tooling | Ubiquitous — every language | Heavy but mature |
| Readability | Higher (usually) | Lower at scale |
When to pick which
- JSON: web APIs, config, mobile, most new systems.
- XML: document-centric data (Office OOXML, DocBook, SVG), SAML, SOAP, finance (FIXML, XBRL), healthcare (HL7), government mandates.
- YAML (3rd option): human-editable config (K8s, CI). More readable than JSON, pickier parser.
- Protocol Buffers / Avro: binary formats — smaller and faster than either, at the cost of requiring schemas for decode.
Notes
- XML is better at mixed content (e.g., "
Hello world
"). JSON needs convention (e.g., objects with "_text" and "children"). - JSON parsing is typically 2–10× faster than XML at equivalent data size.
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