JSON vs XML: What's the Difference?

September 19, 2026

JSON and XML are both formats for representing and exchanging structured data, but they use very different syntax and have different strengths. Every so often a developer has to choose between them — for a new API, a config file, or an integration with someone else's system — or has to work with one when they're used to the other.

The short version: JSON is the default in modern web APIs and JavaScript applications, while XML remains important in a large number of existing systems, document formats, and industry standards. Neither is universally "better." This article compares them side by side — syntax, data types, validation, comments, and typical use cases — so you can tell which one fits a given situation. It assumes you already have a basic idea of what JSON is; if not, our guide to JSON and JSON formatting covers the fundamentals.

What Is JSON?

JSON (JavaScript Object Notation) is a lightweight text format built from objects (key-value pairs), arrays (ordered lists), and a handful of simple values: strings, numbers, booleans, and null. It grew out of JavaScript's object literal syntax, which is a big part of why it became so common for web APIs and browser applications.

{
  "name": "John",
  "age": 30
}

What Is XML?

XML (Extensible Markup Language) represents data as a tree of elements written with opening and closing tags. Elements can nest inside each other, carry attributes (extra name-value information attached to a tag), and contain text. Unlike JSON, XML began as a way to mark up documents, and that heritage shows in its features.

<user>
  <name>John</name>
  <age>30</age>
</user>

The same information can be written using an attribute instead of a child element, for example <user id="42">. Deciding when to use an attribute versus a nested element is a design choice XML leaves to you — JSON has no equivalent, since it has only keys and values.

JSON vs XML Example

The clearest way to see the difference is to represent exactly the same data in both. Here's a user with a name, an age, and a list of skills.

JSON:

{
  "user": {
    "name": "John",
    "age": 30,
    "skills": ["PHP", "JavaScript"]
  }
}

XML:

<user>
  <name>John</name>
  <age>30</age>
  <skills>
    <skill>PHP</skill>
    <skill>JavaScript</skill>
  </skills>
</user>

A few differences are visible immediately:

The JSON version needs an outer "user" key to name the object. In XML, the root element <user> is the name.
JSON writes the list of skills as an array: ["PHP", "JavaScript"]. XML has no array type, so it repeats a <skill> element inside a wrapper element.
XML repeats each name twice (opening and closing tags), which adds up.

That last point shows up in size. Stripped of whitespace, the JSON above is 63 bytes and the XML is 103 bytes. That's a fair illustration of why XML is usually described as more verbose — but it's a property of this particular data, not a rule. Compression such as gzip typically narrows the gap on larger payloads, since repeated tag names compress well, and the size difference is rarely the deciding factor on its own.

JSON vs XML: Key Differences

Feature	JSON	XML
Basic structure	Objects and arrays	Elements and attributes
Syntax	Usually compact	Usually more verbose
Human readability	Generally easy for developers to scan	Structured, but more markup-heavy
Data types	Built-in string, number, boolean, null, object, array	Primarily text; schemas add type information
Comments	Not supported in standard JSON	Supported
Namespaces	No native equivalent	Supported
Ordered lists	Arrays are ordered; object member order shouldn't be relied on	Element order is part of the document
Text mixed with markup	No natural representation	Supported (mixed content)
Common web API usage	Very common	Still used in many APIs and systems
Schema / validation	JSON Schema	XML Schema (XSD), DTD, RELAX NG, and others

None of these rows adds up to a blanket verdict. A format having "more features" isn't an advantage if you don't need them, and a compact format isn't an advantage if it can't express what your data requires.

JSON vs XML Syntax

At the smallest scale, the syntax difference is one key-value pair:

JSON: "key": "value"

XML: <key>value</key>

JSON builds structure from braces ({ }) for objects, brackets ([ ]) for arrays, and colons and commas to separate keys, values, and items. XML builds structure from matching opening and closing tags, and nesting one tag inside another. A few other syntax differences matter in practice:

Top level. A JSON document can be any JSON value at the top level — an object, an array, even a lone string or number. A well-formed XML document must have exactly one root element.
Tags must match. In XML, every opening tag needs a matching closing tag, in the right order, and names are case-sensitive. <user><name>John</user></name> is malformed.
Escaping. JSON escapes with backslashes (\", \\, \n). XML escapes markup characters with entities: <note>Fish & Chips < 10</note> represents the text "Fish & Chips < 10". In JSON the same text is just "Fish & Chips < 10", since & and < have no special meaning there.
Strictness. Both are unforgiving: a single stray character makes a document invalid.

If you're troubleshooting malformed JSON, see Common JSON Syntax Errors and How to Fix Them for practical examples of missing commas, invalid quotes, brackets, and other common problems.

Which Is More Readable?

It depends on the data and who's reading it. Many developers find JSON easier to scan for typical API data — lists of records, settings, nested objects — because there's less markup surrounding the actual values. XML is more verbose, but that markup can also be an advantage: descriptive tags make the meaning of each piece explicit, and XML can express things JSON can't, like attributes, namespaces, and text interleaved with tags.

For a document such as Call John before noon., where formatting tags sit inside running text, XML's approach is natural and JSON has no clean equivalent. For a list of user records returned by an API, JSON is usually the more compact and direct fit. Readability comes down to whether the format matches the shape of your data.

JSON vs XML for APIs

JSON is the common choice for:

REST-style web APIs
Browser and JavaScript applications, where JSON.parse() and JSON.stringify() are built in
Lightweight data exchange between services and configuration files

XML is still found in:

SOAP APIs, whose message format is defined in XML
Enterprise systems and long-running integrations between organizations
Document-oriented standards and file formats — RSS and Atom feeds, sitemaps, SVG images, and the XML files inside Office documents, among others

Note that REST itself doesn't require JSON; an API can follow REST conventions and return XML. JSON is simply the more common choice today. XML APIs are not obsolete — they're widespread wherever the systems on both ends already speak XML, and rewriting a working integration just to change formats is rarely worthwhile.

JSON vs XML: Data Types

This is one of the most important technical differences. JSON has native representations for:

string
number
boolean (true / false)
null
object
array

So "age": 30 is a number and "age": "30" is a string, and the parser knows the difference without any extra information. (JSON has no date type — dates are strings by convention — and the standard doesn't dictate numeric precision, so very large numbers can lose precision in environments that parse them as floating-point.)

XML fundamentally represents data as elements, attributes, and text. In <age>30</age>, the 30 is just characters; nothing in the syntax says whether it's a number, a string, or an ID. Type information comes from outside the document: an XML Schema (XSD) can declare an element as an integer, boolean, or date, and the application interprets the rest by convention. XML also has no built-in null; a common approach is a marker attribute such as <middleName xsi:nil="true"/>. Neither approach is better in the abstract — JSON is simpler when its built-in types are enough, and XML with a schema offers a richer, more explicit type system when you need one.

Binary data is a case where the two agree: neither format can hold raw bytes, so both usually carry it as text encoded in Base64 (see our Base64 encoding guide for how that works).

JSON vs XML: Validation

Both formats can be checked beyond "is the syntax correct?" — for instance, whether a required field is present or a value has the right type — using a schema:

JSON: the common approach is JSON Schema, a separate specification (not part of JSON itself) that describes the expected structure and types.
XML: common approaches include XML Schema (XSD), DTD (an older mechanism with more limited typing), and RELAX NG.

XML's schema ecosystem is older and more mature, and it's often required in enterprise and standards-based contexts. JSON Schema is widely used for API contracts and tooling. In both cases, syntax validation ("is this well-formed?") and schema validation ("does this match the expected structure?") are separate steps.

JSON vs XML: Comments

This is one concrete syntax difference you'll notice quickly. Standard JSON has no comment syntax:

{
  "name": "John"
}

XML supports comments directly:

<!-- User information -->
<user>
  <name>John</name>
</user>

Some JSON-adjacent formats, such as JSONC and JSON5, add comments, but a standard JSON parser will reject them.

JSON vs XML: Which One Should You Use?

There isn't a universal winner. This table shows the choice that's typical in common situations:

Situation	Common choice
Modern web API	JSON
JavaScript application	JSON
REST API	JSON is common
SOAP	XML
Existing XML-based system	XML
Document with namespaces or mixed text and markup	XML may be appropriate
Simple structured API data	JSON is often convenient

The right format depends on the system you're building for, the protocol, the integrations you already have, and the features you actually need. When you're integrating with an existing system, the most useful answer is usually the one it already speaks.

Can JSON and XML Be Converted?

Yes — data can often be transformed from one to the other, and plenty of libraries and services do it. But the conversion isn't always lossless, because the two formats have different data models. Common trouble spots:

Arrays vs repeated elements. XML has no array type. A list with two <skill> elements looks like an array, but a list with a single one looks identical to a plain child element — so a converter can't always tell whether to produce an array or a single value.
Attributes. JSON has no attributes, so converters invent a convention, such as prefixing the key with @. Different tools choose different conventions.
Types. XML values are text, so <age>30</age> could become the number 30 or the string "30", depending on the converter or a schema.
Namespaces. JSON has no native namespace concept, so prefixes must be preserved or flattened somehow.
Mixed content. Text interleaved with elements, like Call John before noon., has no natural JSON form.
Ordering and extras. Element order, comments, and processing instructions may be dropped or handled specially.

Because converters make these choices differently, converting JSON to XML and back doesn't always return the original data exactly. When it matters, check the converted output against what the receiving system expects.

How to Format JSON

If you're working with JSON and want to inspect its structure — an API response, a config file, a payload you're comparing against an XML equivalent — Kravoy's JSON Formatter can validate it, re-indent it, and show it as a collapsible tree. It runs in your browser, so nothing you paste is uploaded. To be clear about scope: it works with JSON only; it doesn't format or convert XML.

Try Kravoy's JSON Formatter →

JSON vs XML: Quick Summary

JSON	XML
Compact syntax	Markup-based
Objects and arrays	Elements and attributes
Common in modern web APIs	Common in SOAP, enterprise, and legacy systems
Standard comments unavailable	Comments supported
JSON Schema available	XSD, DTD, RELAX NG, and others
Easy fit for JavaScript	Strong document and namespace features

Frequently Asked Questions

Is JSON better than XML?

Neither is universally better. The appropriate choice depends on the application, the protocol, and the requirements — JSON suits most modern web APIs, while XML suits document-oriented data and many established systems.

Is JSON faster than XML?

It depends on the parser, the payload, the implementation, and the environment. JSON is more compact for many common data structures, which can mean less to transfer and parse, but that isn't a universal performance guarantee — measure with your own data if speed matters.

Can XML be converted to JSON?

Yes, although some XML features — attributes, namespaces, mixed content, and repeated-versus-single elements — don't map perfectly to JSON, so the result depends on the conversion rules used.

Is XML still used?

Yes. XML remains in use across APIs, enterprise integrations, document formats, and established systems.

Do JSON and XML support the same data types?

Not in exactly the same way. JSON has built-in string, number, boolean, null, object, and array types, while XML relies mainly on text and uses schemas and application rules to define types.

Which is easier to read?

For many typical API payloads, developers find JSON more compact and easy to scan. XML can be clearer for some document-oriented structures where its tags, attributes, and namespaces carry meaning.