JSON vs XML: Key Differences and When to Use Each

Short answer: JSON is lighter and maps straight onto the objects and lists that programming languages already use, which is why it became the default for web APIs and app settings. XML is heavier but can do more: attributes, namespaces, comments, text mixed with markup, and strict schema validation. Pick JSON for a new API. Pick XML when a standard or a partner requires it, or when your data is really a document.

The same data in JSON and XML

Here is one small order written both ways.

{
  "order": {
    "id": 1042,
    "customer": "Acme Ltd",
    "paid": true,
    "items": [
      { "sku": "A-100", "qty": 2, "price": 9.5 },
      { "sku": "B-200", "qty": 1, "price": 24 }
    ]
  }
}

<order id="1042">
  <customer>Acme Ltd</customer>
  <paid>true</paid>
  <items>
    <item sku="A-100" qty="2" price="9.5"/>
    <item sku="B-200" qty="1" price="24"/>
  </items>
</order>

What the comparison shows:

• Types. In JSON, 1042 is a number and true is a boolean. In XML everything is text until a schema says otherwise.
• Lists. JSON has a real list (items). XML just repeats the <item> element, and nothing in the file says "this is a list".
• Two places for data. XML can store a value as an attribute (id="1042") or as a child element. JSON only has keys and values.
• Size. XML repeats every name in a closing tag, so the same data is usually bigger.

JSON vs XML at a glance

	JSON	XML
Full name	JavaScript Object Notation	Extensible Markup Language
Standard	RFC 8259, ECMA-404	W3C Recommendation since 1998
Structure	Objects and arrays	A tree of elements with attributes
Data types	String, number, boolean, null	Text only, types come from a schema
Lists	Native arrays	Repeated elements
Comments	Not allowed	Allowed
Namespaces	No	Yes
Validation	JSON Schema	XSD, DTD, RELAX NG
Query and transform	JSONPath, jq	XPath, XQuery, XSLT
File size	Smaller	Larger
Typical use	Web APIs, app config, NoSQL	Documents, feeds, office files, B2B and government standards

When to use JSON

• You are building or calling a REST or GraphQL API.
• The data goes to a web or mobile app. JavaScript reads it natively with JSON.parse.
• You need a config file people can read and edit (package.json, most tool settings).
• You are writing logs or data streams, often one JSON object per line (JSON Lines).
• You store records in a document database. MongoDB keeps them as BSON, a binary form of JSON.

When to use XML

• A standard requires it: SOAP web services, RSS and Atom feeds, sitemaps, SVG images, and many e-invoicing, banking and tax formats (UBL, ISO 20022, XBRL).
• The data is a document: text with markup inside it, like DocBook or DITA. Word and Excel files are XML too: a .docx or .xlsx is a ZIP of XML files.
• Both sides need strict validation: an XSD schema describes every element and type, and either side can check a file against it.
• The integration already speaks XML: many long-running enterprise and government systems do, and switching formats there brings risk with no real gain.

Is JSON faster than XML?

Usually, yes. A JSON file has fewer characters to read, and its structure maps straight onto native objects, so parsing tends to be quicker, especially in the browser. The real difference depends on the parser and the data. If speed is critical, measure it with your own payloads.

Things that go wrong when you convert

Moving data between the two formats is common, and the same few things trip people up:

• One root. An XML document must have exactly one root element. JSON can start with a list or with several top-level keys.
• Key names. A JSON key like 2024 total is fine, but it is not a valid XML element name (names can't start with a digit or contain spaces), so it has to be renamed.
• Attributes. Going from XML to JSON, attributes become keys with a prefix. Our XML to JSON converter writes @id for an attribute and #text for an element's text by default, and you can change both prefixes.
• One or many. An element that appears once may come out as an object, and the same element appearing twice as a list. Make sure whatever reads the JSON handles both.
• Big numbers. JSON doesn't limit number size, but JavaScript loses precision on integers above 2^53. Keep long IDs as strings.

Convert JSON and XML online

• JSON to XML: turn API data into XML for a system that needs it.
• XML to JSON: turn an XML feed or export into JSON for your app.
• Need a spreadsheet instead? XML to Excel and JSON to Excel turn either format into rows and columns.

Nothing to install: upload a file, pick the indentation you like, and download the result.

Frequently asked questions

What is the main difference between JSON and XML? JSON stores data as objects and arrays with real data types, which makes it compact and easy to use in code. XML stores data as a tree of tagged elements and attributes, which is wordier but supports namespaces, comments, mixed content and schema validation.

Is JSON replacing XML? For new web APIs, mostly yes. XML is still standard in documents, feeds, office files, and regulated data exchange like e-invoicing and banking, so you will keep running into both.

Which is more secure, JSON or XML? Neither format is secure or insecure by itself. XML has more features that need care: when you parse XML from an untrusted source, turn off external entities to avoid XXE attacks. With JSON, the usual risks are in how the parsed data is used.

Can JSON have comments? Not standard JSON. Variants like JSONC and JSON5 allow them, but a strict JSON parser will reject a file with comments.

How do I convert JSON to XML? Open the JSON to XML converter, upload your .json file, and download the .xml file. XML to JSON works the same way in the other direction.