JSON Formatter

What is JSON Formatter?

A JSON formatter (also called a beautifier or pretty-printer) takes compact or minified JSON and re-emits it with consistent indentation, line breaks, and spacing so a human can read it. JSON (JavaScript Object Notation) is the de facto data interchange format for web APIs. A formatter also surfaces syntax errors — if the input is not valid JSON, the parser reports the location and nature of the problem, making it a validator as well.

How It Works

The tool parses the input string with a JSON parser (JSON.parse or a lenient parser that accepts trailing commas and comments). If parsing succeeds, the resulting value is re-serialized with a configurable indent (typically 2 spaces) and sorted-key option. If parsing fails, the parser's error message is displayed with the character offset so the user can locate the issue. All processing is local; no data is sent to a server.

Common Use Cases

• Reading minified API responses — expand a single-line JSON payload into readable, indented output
• Debugging malformed JSON — locate the exact position of a missing comma or bracket
• Comparing config files — consistent indentation makes diffs and reviews easier
• Preparing JSON for documentation — pretty-printed examples are clearer in READMEs and specs

Technical Details

Parser: native JSON.parse (strict, RFC 8259 compliant). Indentation: 2 spaces by default, configurable. Output is UTF-8. The formatter does not sort keys by default to preserve insertion order. Trailing commas and comments are not valid JSON; if present, parsing fails with a syntax error. Maximum practical input size is bounded by browser memory (typically several MB).