XML dominated data interchange in the early 2000s. JSON largely took over for web APIs in the years after, but XML is far from gone. Understanding the differences helps you choose, and read the files you are given.
The same record in both
{
"book": {
"title": "Dune",
"year": 1965,
"authors": ["Frank Herbert"]
}
}
<book>
<title>Dune</title>
<year>1965</year>
<authors>
<author>Frank Herbert</author>
</authors>
</book>
XML wraps everything in named tags with matching start and end markers. JSON uses braces and brackets and keeps names only once.
Differences that matter
Verbosity. XML repeats each element name in both the opening and closing tag, so the same data usually takes more bytes than JSON. Compression narrows the gap but does not remove it.
Data types. JSON has numbers, booleans, null, strings, arrays and objects built in. In XML, everything is text unless a schema says otherwise, so 1965 is a string until something decides it is a number.
Arrays. JSON has a native array. XML expresses lists by repeating elements, which makes a one-item list and a single value look the same.
Attributes versus elements. XML offers two ways to attach data, an attribute such as <book year="1965"> or a child element. JSON has no equivalent distinction, which is simpler but means converting between the two requires choices.
Mixed content. XML can mix text and elements in the same node, as in <p>This is <b>bold</b> text.</p>. That is why XML and its relatives, including HTML, suit documents. JSON cannot represent this naturally.
Comments. XML supports comments with <!-- -->. Standard JSON does not.
Schemas and validation. XML has a mature ecosystem: DTD, XML Schema (XSD) and RELAX NG for describing and validating structure. JSON has JSON Schema, which is widely used but separate from the core format.
Namespaces. XML has namespaces for combining vocabularies without name clashes. JSON has no built-in equivalent.
Querying and transformation. XML has XPath, XQuery and XSLT. JSON tooling such as JSONPath and jq is capable, though less standardised.
Where JSON fits best
- Web and mobile APIs
- Configuration and data files read mostly by programs
- Applications written in JavaScript
- Anywhere a lightweight format is wanted
Where XML fits best
- Documents with structure and text mixed together, such as publishing formats
- Established standards that are defined in XML: office document formats are zipped XML, SVG graphics are XML, and many industry and government data exchanges still use it
- Systems that need strong schema validation and namespaces
- Legacy integrations, such as SOAP services
Reading either format
Both are plain text. Open them in any editor, or use Docento's Text & Markdown Editor, which checks both JSON and XML syntax and shows the line where parsing fails. For help reading XML, see how to open and read XML files.
Converting between them
Converting is mechanical for simple data but ambiguous in general: attributes, repeated elements, mixed content and text-only values must be mapped by convention. Expect to review the output.
Takeaway
JSON is lighter, has native types and arrays, and dominates APIs. XML is richer, with attributes, mixed content, namespaces and strong schemas, and remains the right tool for documents and many standards. Choose by the data and the ecosystem you must interoperate with.
