JSON vs XML
JSON and XML are both text formats for storing and exchanging structured data, but they take different approaches. JSON uses lightweight key/value pairs and arrays that map directly onto programming-language data structures; XML wraps data in nested tags and can also carry attributes, namespaces, and comments. In short: JSON won the web-API era for being compact and native to JavaScript, while XML remains a good fit for documents, configuration, and systems that need schemas.
Side-by-side comparison
| Aspect | JSON | XML |
|---|---|---|
| Format | Data format (key/value pairs, arrays) | Markup language (nested tags) |
| Verbosity | Compact; no closing tags | Verbose; every element has a closing tag |
| Data types | String, number, boolean, null, array, object | Everything is text; types are by convention |
| Arrays | First-class ([ ]) | Repeated elements; no native array |
| Comments | Not allowed | Allowed (<!-- -->) |
| Attributes | No; everything is a value | Yes (id="1") |
| Namespaces | No | Yes |
| Schema/validation | JSON Schema | XSD, DTD, RELAX NG |
| Parsing | Fast; native in browsers | Slower; heavier parsers |
| Typical use | Web/mobile APIs, config, data interchange | Documents, SOAP, enterprise/legacy, RSS |
The same data in JSON and XML
The same record, first as JSON, then as XML:
{
"id": 42,
"name": "Ada",
"active": true,
"roles": ["admin", "editor"]
}<user id="42">
<name>Ada</name>
<active>true</active>
<roles>
<role>admin</role>
<role>editor</role>
</roles>
</user>Notice the XML version is longer, repeats the role tag for each array item, and stores the id as an attribute. The JSON version is shorter and its true is a real boolean, not text. You can convert between the two with XML to JSON and JSON to XML.
Key differences
- Size: JSON is typically 30 to 50 percent smaller than the equivalent XML, which matters over the wire.
- Types: JSON has real numbers, booleans, and null; in XML everything is text until a schema says otherwise.
- Arrays: JSON has native arrays; XML repeats elements and offers no built-in "this is a list" signal.
- Metadata: XML has attributes, namespaces, and comments; JSON keeps everything as plain values.
- Tooling: browsers parse JSON natively with
JSON.parse; XML needs a DOM or SAX parser.
When to use JSON
- REST and GraphQL APIs, and any browser or mobile client.
- Configuration files (
package.json,tsconfig.json). - Storing and exchanging structured data between services.
- Anywhere payload size and parse speed matter.
When to use XML
- Document-centric formats with mixed text and markup (for example HTML, DocBook, RSS).
- Systems that require schemas, namespaces, or digital signatures.
- Legacy or enterprise integrations (SOAP web services, many government and finance systems).
Is JSON replacing XML?
For web APIs, largely yes: most public APIs now default to JSON. But XML is far from dead. It still powers document formats, enterprise messaging, office file formats (.docx and .xlsx are zipped XML), and countless legacy systems. The practical answer is to use JSON for new APIs and data interchange, and XML where a standard, schema, or existing system calls for it.
Working with JSON and XML
- XML to JSON: convert an XML document into a JSON object.
- JSON to XML: convert JSON into well-formed XML.
- What is JSON?: a plain-language primer on the format.
- JSON Formatter: pretty-print, validate, and minify JSON.
Frequently asked questions
What is the main difference between JSON and XML?
JSON stores data as key/value pairs, arrays, and primitive types that map directly onto the data structures of most programming languages. XML is a markup language that wraps data in nested tags and can also carry attributes, namespaces, and comments. JSON is more compact and faster to parse; XML is more expressive for documents and mixed content.
Is JSON better than XML?
Neither is universally better; they solve different problems. For web and mobile APIs, config, and data interchange, JSON is usually the better fit because it is lighter and native to JavaScript. For document-centric formats, legacy enterprise systems (SOAP), and cases needing schemas, namespaces, or mixed content, XML is still a strong choice.
Is JSON faster than XML?
Generally yes. JSON is less verbose, so payloads are smaller and parsing is typically faster and less memory-intensive, especially in browsers where JSON.parse is highly optimized. The gap depends on the data and parser, but for typical API payloads JSON wins on size and speed.
Can JSON represent everything XML can?
Not exactly. XML has attributes, namespaces, comments, processing instructions, and mixed content (text interleaved with elements) that have no direct JSON equivalent. Converting XML to JSON usually maps attributes to specially named keys. For plain structured data, both formats are equivalent.
Should I use JSON or XML for a REST API?
JSON, in almost all cases. It is the de facto standard for REST APIs: smaller responses, native browser support, and first-class handling in every modern framework. Reach for XML only when a specific protocol or partner system requires it (for example SOAP).