Format & documents

JSON formatter & validator — preserve large integers

Format, minify and validate JSON online. Inspect a tree view and locate syntax errors by line and column. Preserve large integers locally, with no sign-up.

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How to use

Paste JSON and choose Format or Minify. Expand objects and arrays in Tree view. Numbers and key order are preserved as written.

Your input stays yours

Step by step

Paste an API response or choose Load example, using the original JSON text.
Choose Format to validate syntax and apply two-space indentation. Use the reported line and column to locate an error.
Expand objects and arrays in Tree view, or choose Minify to remove whitespace outside strings. Then copy or download the result.

Try it: an API response with a large integer

{"orderId":9007199254740993,"status":"ready","items":[{"sku":"A-01","count":2}]}

After formatting or minifying, orderId should still read 9007199254740993. This tool preserves the number text instead of converting it to a JavaScript Number before output.

Frequently asked questions

Why are single quotes, comments or trailing commas rejected?

This tool validates standard JSON, rather than JSON5 or JSONC. Use double quotes for keys and strings, remove comments and omit the comma after the final member. NaN, Infinity and undefined are not JSON values.

Can formatting recover digits that were already lost?

No. The tool preserves the text you paste. It cannot restore digits already rounded by another program. Obtain the original response; consider strings when passing large integer identifiers between systems.

Does valid JSON mean the API will accept it?

Validation checks JSON syntax, not JSON Schema, required fields, business rules or duplicate keys. Check the API contract separately. Formatting preserves the original key order and does not merge duplicate keys.

Is input uploaded, and how large can it be?

JSON runs in your browser; editor contents are not sent to servers or analytics. The processing limit is 1,000,000 UTF-16 code units, measured as JavaScript string length. Deep nesting can still affect responsiveness.