Free JSON Formatter Online

Parse JSON, produce readable indentation or a compact one-line result, and expose syntax errors before the output is copied into code or an API client.

Browser-localFreeNo upload required

Tool workspace

JSON input

Result

What this tool is for

Parse JSON, produce readable indentation or a compact one-line result, and expose syntax errors before the output is copied into code or an API client.

How to use

Paste a complete JSON value, not a JavaScript object literal.
Choose Format for indentation or Minify for compact output.
If parsing fails, use the browser error position to correct the source and run it again.

Example

Format `{"name":"Ada","roles":["admin","editor"]}` to inspect the nested array, then minify the same value for transport.

FAQ

Does it accept comments or trailing commas?

No. Those are not valid JSON and will produce a parse error.

Can the root be an array or primitive?

Yes. Any value accepted by JSON.parse is supported.

Reproducible examples

Known inputs and expected results

Run these examples in the workspace above and compare the result with the documented output.

Format a nested value

Input: {"user":{"name":"Ada"},"roles":["admin","editor"]}
Options: Choose Format with two-space indentation.
Action: Parse and format.
Expected output: A multiline JSON document with nested object and array indentation.
Explanation: Whitespace changes, but parsed keys and values remain equivalent.

Minify an array

Input: [ { "id": 1 }, { "id": 2 } ]
Options: Choose Minify.
Action: Parse and compact.
Expected output: [{"id":1},{"id":2}]
Explanation: Insignificant spaces are removed after successful standard JSON parsing.

Error or unsupported case

JavaScript-like syntax

Input: {name:'Ada',}
Expected error or limit: Unquoted keys, single quotes, and the trailing comma are rejected by JSON.parse.
Safer alternative: Convert the input to standard JSON or use a JSON5-aware parser.

When not to use this tool

JSON Schema or application business-rule validation
Lossless handling of integers beyond JavaScript's safe range

Algorithm and assumptions

The tool uses standard JSON.parse and JSON.stringify, accepts any JSON root type, formats with two spaces, and does not promise semantic object-key ordering.

Input and output

Input must be valid JSON. Output is semantically equivalent formatted or minified JSON; object key order is not intentionally changed.

Supported formats and behavior

Objects, arrays, strings, numbers, booleans, and null
Readable two-space indentation
Compact single-line output

Limits

JSON5 and JavaScript syntax are not supported
Very large input may be constrained by browser memory

Edge cases and common errors

Duplicate object keys resolve according to JSON.parse behavior
Large integers can lose precision in JavaScript
Invalid escape sequences are rejected

Release testing

Release checks cover valid objects and arrays, invalid property syntax, primitive roots, formatting, minifying, copy, and clear actions.

Privacy boundary

The input and result stay in this browser session. ZZP Box does not upload or store the values entered in this tool.

Related reviewed tools

Choose the next tool by the operation you need, then review that page's stated input and limits.