Format, validate, minify, copy, and download JSON in your browser without silently rounding large integer tokens or discarding duplicate object names.
Paste minified, unformatted, or broken JSON into the editor. It accepts valid JSON objects, arrays, strings, numbers, booleans, null values, and nested structures within your browser's available memory.
Choose spaces or a real tab, then click Format for readable indentation. Invalid input shows the browser's parsing message and adds line and column details when an error position is available.
Copy the result, download it as a .json file, or minify it to remove insignificant whitespace. Whitespace inside strings and the original number tokens remain unchanged.
| Type | Example | Notes |
|---|---|---|
| Object | {"key": "value"} | Keys must be double-quoted strings |
| Array | ["a", "b", "c"] | Ordered list of values |
| String | "hello world" | Must use double quotes, not single |
| Number | 42 or 3.14 | Large or high-precision values may exceed a receiver’s exact numeric range |
| Boolean | true or false | Lowercase only |
| Null | null | Lowercase only |
RFC 8259 identifies integers from −(253−1) through 253−1 as the range where common binary64 implementations agree exactly. A formatter that parses and re-stringifies larger identifiers can silently change their digits. Mizakii formats the original number token instead.
RFC 8259 says object names should be unique because receivers disagree about duplicates. This tool preserves duplicates and shows a warning rather than silently keeping only the last value.
Primary references: RFC 8259 and the ECMAScript JSON specification.
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