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JSON Syntax Validator

Validate JSON syntax with exact line, column and path, catch duplicate keys and format or minify — in your browser.

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Everything runs in this browser tab — nothing is uploaded. Duplicate keys are legal JSON, but most parsers silently keep the last value, so this tool lists them.

About the JSON Syntax Validator

Paste any JSON document into the box above and this validator tells you immediately whether it is syntactically valid — and if it is not, exactly where it breaks. Instead of a vague parse error it shows the line, the column, the path inside the document (for example $.orders[2].total) and a snippet with a caret under the offending character. It also counts objects, arrays, property names and nesting depth, flags duplicate keys that most parsers silently collapse into one value, and warns when an integer is too large for JavaScript to represent exactly. Everything runs locally in this browser tab, so confidential payloads never leave the page, and a valid document can be formatted with two or four spaces (or tabs), minified, copied and downloaded again as a .json file.

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