JSON Formatter / Validator
Format, minify, and validate JSON with readable errors. Everything is processed locally in a background worker.
Processed on your device. Your files and inputs never leave your browser.
How it works
Paste a JSON document
Choose Format, Minify, or Validate. Parsing runs off the main browser thread.
Copy the output or download a .json file. Clear removes both input and output.
JSON requires double-quoted keys and strings. Comments, trailing commas, undefined, and NaN are not valid JSON. This tool uses JavaScript JSON semantics: duplicate keys resolve to the last value, and numbers outside JavaScript's safe integer range can lose precision during formatting. Store exact large identifiers as strings. Large inputs are processed in a terminable worker; only a preview of very long output is rendered.
A few more useful tools
Good to know
Does this support JSON5 or comments?
No. Validation follows standard JSON syntax. Remove comments and trailing commas before formatting.
Are large integers preserved exactly?
JavaScript numbers cannot represent every integer above 9,007,199,254,740,991. Use quoted strings for exact identifiers or amounts beyond that range.