Rechnerpilot tool

JSON Formatter

Check JSON for validity and display it formatted with indentation – locally in the browser, with no data transmission.

Developer Tools

Indentation

Enter JSON to validate and indent it.

Explanation

How JSON Formatter works

JSON (JavaScript Object Notation) is a text-based data format defined in RFC 8259. This tool checks whether an input is valid JSON and then outputs it indented ("Pretty-Print"). The values themselves remain unchanged.

In the event of a syntax error, the parser's message is displayed, with line and column where possible, to quickly find the location of the error. Typical causes are single instead of double quotes, missing or excess commas, and comments, which JSON does not allow.

Limitations of this tool

Validation and indentation only — deliberately no minify.
Strict JSON standard — no comments, no trailing comma.
No schema matching and no semantic validation of the values.

Sources

RFC 8259: The JavaScript Object Notation (JSON) Data Interchange Format. IETF, 2017.
ECMA-404: The JSON Data Interchange Syntax.

Practice

Practical examples

Indent compact JSON

{"a":1,"b":[2,3]} is displayed readably with two-space indentation.

Check validity

A missing comma or an open bracket is reported with line and column.

Nested objects

Deeply nested structures are indented consistently and remain unchanged.

FAQ

Frequently asked questions

Does the formatter change my data?

No. The formatter parses the JSON and outputs exactly the same values indented. The order of object keys and values is preserved.

Can I minify JSON?

No. This tool only checks validity and displays valid JSON indented. A minify function is deliberately not included.

Is the data sent to a server?

No. Processing takes place entirely locally in the browser using JSON.parse and JSON.stringify. No data is transmitted.

Why is an error reported?

The parser follows the strict JSON standard (RFC 8259). Common causes are single instead of double quotes, superfluous or missing commas, and comments, which JSON does not allow.

Are comments supported?

No. The JSON standard does not know comments. If the input contains comments, the parser reports a syntax error.

Tips

Good to know

JSON requires double quotes for keys and strings.
Comments are not allowed in JSON.
Indentation only changes the presentation, not the data.

Related calculators