JSON formatter: make your response readable.
Validate and pretty-print a JSON response, or minify it for a fixture. Choose two or four spaces and export the result — free, no sign-up.
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Strict JSON. Large numbers follow JavaScript precision; duplicate keys keep their last value.
How to use
- Paste a JSON value, object or array.
- Choose two spaces, four spaces or minified output, then Format JSON.
- Read any validation error, or copy and download the valid result.
Frequently asked questions
Is this free, and do I need an account?
It is free, no sign-up. Processing happens in your browser. Tool inputs and results are not sent to a processing API or saved by this tool. Usage analytics record only the tool name and action.
Does it validate JSON syntax?
Yes. Native JSON parsing rejects trailing commas, comments, unquoted keys and other invalid JSON. This checks syntax, not a JSON Schema or your business rules.
Can I minify JSON?
Yes. Choose Minified to remove unnecessary whitespace. Whitespace inside string values is preserved.
Can I use JSON with comments?
No. JSONC and JSON5 are different formats. Remove comments and trailing commas before using this strict JSON formatter.
Will numbers and duplicate keys be preserved exactly?
Native JavaScript JSON parsing can round integers beyond the safe integer range and keeps the last duplicate key. Encode large identifiers as strings and avoid duplicate keys.
How large can the input be?
Use a sample under 1 MB with at most 100 nesting levels and 100,000 values. Very large documents belong in a local streaming tool.
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