JSON Formatter

Validate JSON syntax and convert it to readable or compact output.

Reviewed: 2026-07-21

Method and assumptions

Use a lossless JSON parser that preserves large integer values while checking RFC 8259 syntax, then pretty-print with two or four spaces or remove insignificant whitespace for compact output. This checks syntax, not property meaning or compliance with an external schema. Text within the size limit is processed locally, so API responses and configuration values are not sent to our server.

How to use it

Paste or type the original JSON into the input area.
Choose validation, readable formatting, or one-line minification.
Review the status and output, then copy it or download a JSON file.

When it helps

Making an API response easier to inspect
Finding comma or quotation errors in a configuration file
Removing unnecessary whitespace before transmission

How to verify the result

Check input units and reference dates first. For an important decision, compare the result with an official source or original document. A rounded display can differ slightly from the underlying value.

Official references

RFC 8259 JSON standard

Frequently asked questions

Why can valid JavaScript object syntax still fail as JSON?

RFC 8259 JSON requires double quotes for property names and strings, and it does not allow comments, functions, undefined, or trailing commas.

Does this tool validate a JSON Schema?

No. It only checks whether the text can be parsed as JSON. Schema rules such as required properties and value types need a dedicated validator.

Is my API data stored?

No. Parsing and transformation happen in the current browser. On a shared device, still take care not to leave sensitive values visible or in the clipboard.