JSON Formatter

Paste JSON to format, minify, or validate it. The tool scans the document without converting number literals, so large integers keep their exact value and malformed input is reported instead of silently changed.

How it works

• A purpose-built scanner tokenizes the document without turning number literals into JavaScript numbers.
• The structure is checked for trailing content, duplicate keys, and syntax errors before anything is reformatted.
• Format re-emits the tokens with your chosen indentation; Minify removes all optional whitespace.

Methodology

1. Tokenize the JSON document in a single pass, keeping number literals as text so no value is rounded.
2. Validate the token stream against the JSON grammar of RFC 8259 and ECMA-404 before any transformation.
3. Re-emit the original tokens with the requested indentation, or strip optional whitespace for minification.

Usage

1. Paste or type a JSON document.
2. Choose format or minify, and set an indentation size for format.
3. Review the result or the positioned error before copying or downloading.

Examples

Large integer preserved

{"orderId":9007199254740993,"enabled":true}

Limitations

Why JSON formatting is not just whitespace

Formatting JSON is a review aid: consistent indentation makes diffs readable and exposes structural mistakes. It becomes unsafe when the formatter parses numbers through JavaScript numbers, because identifiers such as order ids and high-precision decimals then change value without warning.

This tool scans the document, validates its structure, and re-emits the original literals, so what you see is what was there.