JSON formatter and validator
Format, minify and validate JSON while preserving large numbers and rejecting duplicate keys.
How to use
Paste JSON, choose formatting, minification or validation without changes, then process. Review the result before copying or downloading JSON.
The input {"n":9007199254740993,"ok":true} retains the number 9007199254740993 exactly as written, without rounding.
Support & limits
JSON grammar follows RFC 8259 without converting numeric values to Number. Duplicate names within one object are rejected even when encoded using Unicode escapes. Key order and number/string spellings are retained; only whitespace outside strings changes.
Common questions
Are large numbers or duplicate keys lost?
Number lexemes remain identical to the input, including exponents and significant zeroes. A duplicate key produces a clear error until you resolve it; the tool never chooses a value for you.
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