JSON vs. XML vs. YAML: Which Data Format Should You Use?

JSON, XML, and YAML are the three formats you will meet most often when moving structured data between systems. They can all represent the same information, yet each has a personality that makes it better suited to certain jobs. Here is a clear comparison to help you choose.

The same data, three ways

A small configuration in JSON:

{
  "service": "api",
  "port": 8080,
  "tags": ["web", "public"]
}

The same data in XML:

<config>
  <service>api</service>
  <port>8080</port>
  <tags>
    <tag>web</tag>
    <tag>public</tag>
  </tags>
</config>

And in YAML:

service: api
port: 8080
tags:
  - web
  - public

Three formats, identical meaning — but very different ergonomics.

JSON: the web’s default

Strengths: compact, unambiguous, parses natively in every language, and maps directly to objects and arrays. It is the lingua franca of REST APIs and JavaScript apps.

Weaknesses: no comments, somewhat noisy punctuation (braces, quotes, commas), and easy to break with a trailing comma.

Use it for: APIs, browser-to-server communication, anything programmatic.

XML: verbose but powerful

Strengths: supports attributes, namespaces, mixed content, and a rich validation/transformation ecosystem (XSD, XSLT, XPath). It is self-describing and well suited to documents.

Weaknesses: verbose, with closing tags doubling much of the markup. Parsing is heavier, and it maps awkwardly to native data structures.

Use it for: document-centric formats (RSS, SVG, office files), legacy enterprise systems, and SOAP services.

YAML: human-friendly configuration

Strengths: minimal punctuation, supports comments, and is pleasant to read and hand-edit. It is the format of choice for configuration in tools like Docker Compose, Kubernetes, and CI pipelines.

Weaknesses: significant whitespace makes it error-prone — a stray space can change meaning or break parsing. It also has surprising edge cases (the famous “Norway problem” where no becomes false).

Use it for: configuration files that humans edit by hand.

Side-by-side

	JSON	XML	YAML
Readability	Good	Fair	Excellent
Verbosity	Low	High	Lowest
Comments	No	Yes	Yes
Whitespace-sensitive	No	No	Yes
Native to JS	Yes	No	No
Schema/validation	JSON Schema	XSD (mature)	JSON Schema
Best for	APIs	Documents	Config

They convert easily

Because all three model the same tree of objects, arrays, and scalars, converting between them is routine. YAML is famously a superset of JSON, so any valid JSON is also valid YAML. Many config tools accept either interchangeably.

Where merging fits in

If you work with JSON specifically, combining multiple documents is a frequent need — layering config, aggregating API responses, consolidating data. Our merge tool handles that entirely in the browser. (For YAML config, a common pattern is to convert to JSON, merge, and convert back — the merge semantics are the same.) If you are new to the format, start with our primer on what JSON is.

The verdict

Reach for JSON when machines talk to machines, YAML when humans edit configuration, and XML when you need documents, attributes, or a mature validation toolchain. None is universally best — match the format to the job.