JSON vs YAML: Which Format Should You Use?
JSON and YAML both describe structured data, but they optimise for different jobs. JSON is strict and universal; YAML is human-friendly and comment-friendly. This guide compares them and shows how to convert between the two.
JSON vs YAML: Which Format Should You Use?
JSON and YAML both describe structured data, but they optimise for different jobs. JSON is strict and universal; YAML is human-friendly and comment-friendly. This guide compares them and shows how to convert between the two.
Syntax at a glance
JSON uses braces and quotes: {"name": "Ada", "age": 36}. YAML uses indentation and optional quotes: name: Ada on one line and age: 36 on the next. YAML is a superset of JSON, so any valid JSON is also valid YAML - but not the other way round.
Comments and readability
JSON has no comments, which is fine for data but awkward for configuration. YAML supports # comments and multi-line strings, so it reads better for files humans edit by hand, such as CI pipelines and Kubernetes manifests.
Types and gotchas
JSON has one number type; YAML distinguishes integers and floats and adds booleans, null and dates. YAML’s indentation rules are strict - a stray tab or a missing space breaks the file - and unquoted values like yes, no or on can be parsed as booleans.
When to use JSON
Choose JSON for REST and GraphQL APIs, browser storage, and anywhere a machine parses the data. Its strict grammar means fewer surprises and every language has a built-in parser.
When to use YAML
Choose YAML for configuration files a person maintains: Docker Compose, GitHub Actions, Ansible and Kubernetes. Convert to JSON when a tool or API needs it, and back to YAML for editing.
Frequently asked questions
Is YAML a superset of JSON?
Yes. Every valid JSON document is valid YAML, which is why conversion from JSON to YAML is always safe.
Why does my YAML fail to parse?
Usually indentation: tabs are not allowed, and a missing space after the colon breaks the mapping. Check the first error line the parser reports.
Can I convert between them offline?
Yes. The DailyWebKit converters run in your browser; your data is never uploaded.
Which is better for config files?
YAML, because it supports comments and multi-line strings. Use JSON when a machine consumes the file.