JSON vs XML vs YAML: Which Should You Use?

By Sibtain Ali · Published July 22, 2026 · Updated August 31, 2026

Short version: JSON for APIs and data exchange, YAML for configuration that humans edit, XML when a system or a standard requires it. All three describe structured data as text. What separates them is who they were optimized for. Here is the same record in each, followed by the trade-offs that fall out of the syntax.

The same data, three ways

// JSON
{
  "service": "payments",
  "replicas": 3,
  "regions": ["eu-west", "us-east"]
}

# YAML
service: payments
replicas: 3
regions:
  - eu-west
  - us-east

<!-- XML -->
<config>
  <service>payments</service>
  <replicas>3</replicas>
  <regions>eu-west</regions>
  <regions>us-east</regions>
</config>

JSON: the data exchange default

Minimalism and universality are the whole pitch. The grammar fits on an index card, every language parses it natively or nearly so, and its data model of objects, arrays, strings, numbers, booleans and null maps straight onto structures programs already use. Parsing is fast and unambiguous. The weaknesses are deliberate omissions: no comments, no date type, and enough punctuation that editing a large document by hand becomes a chore. For machine-to-machine exchange that is precisely the right trade, which is why essentially every modern API speaks JSON.

YAML: the configuration favorite

YAML optimizes for whoever has to edit the file. Indentation replaces braces, quotes are usually optional, and comments are first-class. Those are the three things you want when maintaining a config by hand, and they are why Kubernetes, Docker Compose, GitHub Actions and Ansible all landed on it.

The cost is complexity. The spec is enormous, indentation mistakes change meaning silently, and unquoted scalars can surprise you: the classic case is country: NO parsing as boolean false in YAML 1.1 tools. YAML 1.2 is a superset of JSON, so any JSON document is already valid YAML, and converting in that direction (what the JSON to YAML converter does) loses nothing.

XML: the enterprise standard

XML predates both and carries machinery neither has: XSD schemas that formally validate structure, namespaces for mixing vocabularies, attributes, and mature tooling in XPath and XSLT. It is still the required format across large stretches of enterprise and government integration, including SOAP services, invoicing standards, RSS, sitemaps and the internals of Office documents.

The price is verbosity. Every element name gets written twice, so XML documents run considerably larger and take longer to read and parse. New projects rarely pick it. Plenty of existing systems still demand it, and the JSON to XML converter exists for exactly those boundaries.

Feature comparison

How to decide

Ask who reads the file most.

Machines exchanging data want JSON: smallest spec, fastest parsers, support everywhere. Humans maintaining configuration want YAML, where comments and clean syntax pay off daily and a linter keeps the quirks in check. A counterparty, regulator or legacy system that specifies XML gets XML, because fighting a mandated format costs more than using it.

Mixed pipelines are normal. Generate your data as JSON and convert at the boundary to whatever the destination needs. If JSON itself is still new to you, What Is JSON? covers the foundations.