JSON Formatter & Validator
Validate, pretty-print, and minify JSON with configurable indentation and clear syntax errors.
JSON is parsed only in your browser. Nothing is logged or uploaded.
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Validation versus schema validation
This tool validates JSON syntax. Valid syntax does not mean the data matches an API contract or JSON Schema. Top-level scalars such as 42, "hello", true, and null are valid JSON values.
Formatting and minifying
Formatting parses the input and serializes it with the selected indentation. Minifying removes insignificant whitespace while preserving whitespace inside strings. Neither operation is a byte-for-byte transformation: JavaScript may change the lexical representation of very large numbers.
Frequently asked questions
Why did my large integer change?
JavaScript numbers are IEEE 754 doubles. Integers beyond the safe range can lose precision when parsed. Do not use this tool for exact 64-bit identifiers without verifying the output.
Why is trailing comma JSON rejected?
Trailing commas are not part of standard JSON syntax, even though some JavaScript configurations accept them.
Is my JSON uploaded?
No. Parsing and formatting happen in the browser.