Guide

JSON vs YAML vs XML

JSON, YAML, and XML all represent structured data, and you can convert between them, but they are not interchangeable in practice. Each has a shape that fits some jobs better than others. This guide compares them so you can pick with a reason.

Want to try it while you read?Open the JSON Converter

The same data in all three

Start with one record expressed three ways.

{
  "book": {
    "title": "Dune",
    "year": 1965,
    "inPrint": true
  }
}

book:
  title: Dune
  year: 1965
  inPrint: true

<book>
  <title>Dune</title>
  <year>1965</year>
  <inPrint>true</inPrint>
</book>

JSON is compact and typed. YAML is the lightest to read. XML is the most verbose because every value is wrapped in an opening and closing tag.

JSON: the default for APIs

JSON won the web API space because it is compact, has clear types, and every language parses it quickly. It maps directly onto the objects and arrays that programs already use, so there is little friction between the wire format and your code.

Its limits are the flip side of its simplicity. There are no comments, no schema built into the format, and no way to attach metadata to a value without adding another field. For data exchange, none of that matters much, which is why JSON is the default choice.

YAML: the default for config

YAML is built for files people edit by hand. It supports comments, its indentation makes structure obvious, and it carries less punctuation per line than JSON. That is why it dominates configuration for tools like Kubernetes, Docker Compose, and CI pipelines.

The trade-off is that YAML's flexibility can bite. Indentation is significant, so a stray space changes meaning, and its type guessing can turn a value like no into a boolean if it is not quoted. For machine-to-machine data, that ambiguity is a reason to prefer JSON.

XML: still where integrations expect it

XML predates both and is more verbose, but it has features they lack. It distinguishes attributes from element content, supports namespaces, and has a mature validation ecosystem with schemas and XPath for querying. Many enterprise systems, document formats, and older SOAP integrations are built on it.

If you are integrating with a system that speaks XML, you use XML. For a new API of your own, its weight is usually more than the job needs.

How to choose

Building or consuming a web API: JSON.
Writing a config file people will maintain by hand: YAML.
Integrating with a system that already uses XML, or needing attributes, namespaces, or mature schema validation: XML.

Because they describe the same kinds of data, you are rarely locked in. You can convert JSON to YAML or XML when a downstream tool wants a different format and keep working in whichever one suits the task.

FAQ

Which is fastest to parse?

JSON is generally the fastest and has the widest, most optimized parser support. YAML parsing is heavier because the grammar is richer, and XML is verbose enough that documents are larger for the same data.

Can I convert between all three?

Yes, for the data itself. Features unique to one format, like YAML comments or XML attributes and namespaces, may not have a clean equivalent in the others.

Is YAML better than JSON?

Neither is better in general. YAML is nicer for hand-edited config, JSON is better as a strict wire format for machines. They fit different jobs.