JSON Formatter

The errors that break most JSON

JSON is stricter than the JavaScript it resembles. A comma after the last item, single quotes, keys without quotes, comments, and values like undefined or NaN are all invalid, and each is reported with its position. Text copied from a JavaScript file or produced by a language model often has several of these; the JSON repair tool fixes them mechanically, and JS object to JSON converts object literals.

Large numbers lose digits

JavaScript stores every number as a 64-bit float, which is exact only up to 9,007,199,254,740,991. Any tool that parses JSON in JavaScript, this one included, rounds larger integers, so a 64-bit ID such as 12345678901234567890 comes back as 12345678901234567000. APIs that return large IDs usually offer them as strings for this reason.

Beyond formatting

Formatting proves the syntax is valid, not that the data has the right fields. To check structure against a contract, use the JSON Schema validator; to see what changed between two responses, the JSON diff compares by key rather than by line.

How to use it

1. Paste JSON into the input editor.
2. Choose Format JSON or Minify.
3. Review the parse result, then copy or download it.

Privacy & limitations

Your JSON stays in your browser. Formatting checks syntax, not whether fields match a particular API schema.