JSON vs XML vs YAML: Which Should You Use?

Updated July 22, 2026

Short version: use JSON for APIs and data exchange, YAML for configuration humans edit, and XML when a system or standard requires it. All three describe structured data as text; they differ in who they are optimized for. Here is the same record in each format, then the trade-offs that follow from 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

JSON’s strengths are minimalism and universality. The grammar fits on an index card, every language parses it natively or nearly so, and its data model (objects, arrays, strings, numbers, booleans, null) maps directly onto the structures programs already use. Parsing is fast and unambiguous. Its weaknesses are deliberate omissions: no comments, no date type, and enough punctuation that hand-editing large documents is tedious. That trade-off is exactly right for machine-to-machine exchange — which is why essentially every modern API speaks JSON.

YAML: the configuration favorite

YAML optimizes for the human editing the file. Indentation replaces braces, quotes are usually optional, and comments are first-class — the three things you want when maintaining a config by hand. That is why Kubernetes, Docker Compose, GitHub Actions and Ansible all chose it. The cost is complexity: the YAML spec is enormous, indentation errors change meaning silently, and unquoted scalars can surprise you (the classic: country: NO parsing as boolean false in YAML 1.1 tools). YAML 1.2 is a superset of JSON, so any JSON document is technically valid YAML — converting between them, as the JSON to YAML converter does, is lossless in that direction.

XML: the enterprise standard

XML predates both and carries machinery they lack: schemas (XSD) that formally validate structure, namespaces for mixing vocabularies, attributes, and a mature tooling ecosystem (XPath, XSLT). It remains the required format in large swaths of enterprise and government integration — SOAP services, invoicing standards, RSS, sitemaps, Office document internals. The price is verbosity: every element name is written twice, so XML documents run significantly larger and are slower to read and parse. New projects rarely choose XML, but plenty of systems still demand it — the JSON to XML converter exists for exactly those boundaries.

Feature comparison

How to decide

Ask who reads the file most. Machines exchanging data → JSON: smallest spec, fastest parsers, universal support. Humans maintaining configuration → YAML: comments and clean syntax matter daily, and the format’s quirks are manageable with a linter. A counterparty, regulator or legacy system that specifies XML → XML: fighting a required format costs more than using it. Mixed pipelines are normal — generate data as JSON, convert to whatever the destination needs at the boundary. If you are still getting comfortable with JSON itself, What Is JSON? covers the foundations.