JSON formatter
Formats and minifies JSON with syntax validation. Precise error message with line and column. Statistics on keys and nesting depth.
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Formatter and validator
Action
Indent
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Document statistics
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About the JSON format
Data types
7 types"str" · 42 · true · null · [ ] · { }
JSON supports 7 types: string, number, boolean, null, array, object. Numbers are unquoted; strings always use double quotes. Single quotes, comments, undefined and NaN are not part of the standard (JSON5 only).
Common mistakes
How to fixtrailing , · 'quotes' · {key: 1}
Trailing comma after the last element, single quotes instead of double, unquoted keys. Standard JSON.parse rejects them. JSON5 allows all of this, but it's not a web standard — only for configs.
Format / minify
20–40%{"a":1} → {\n "a": 1\n}
Formatted JSON — for development: easy to read and diff in git. Minified — for API responses and network traffic. Savings are typically 20–40% and much more on large payloads.
JSON vs YAML/XML
When whichAPI → JSON · config → YAML/TOML
JSON — best for APIs and service-to-service data: minimal, everyone parses it, no ambiguity. YAML/TOML — for configs (comments, readability). XML — legacy enterprise/SOAP, usually overkill for new work.