JSON Formatter

Free JSON formatter and validator. Paste any JSON to format it with proper indentation, detect errors, and beautify minified JSON.

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This tool has a free JSON API. Copy a prompt or skill below to use it with ChatGPT, Claude, or any AI agent — no API key needed.

API docs
Paste your JSON above.

How json formatter works

JSON (JavaScript Object Notation) is the standard data format for web APIs and configuration files. Minified JSON, with no spaces or line breaks, is efficient for transmission but hard to read. This formatter parses your JSON and re-serializes it with proper indentation and line breaks.

Enter or paste any JSON string. The formatter parses it using the standard JSON parser (which catches syntax errors like missing commas, unmatched braces, and trailing commas), then re-outputs it with 2-space indentation by default. You can adjust the indent size. If the JSON is invalid, the error message tells you where the problem is.

The formatter preserves the key order of your original JSON. Everything runs in your browser using the built-in JSON.parse and JSON.stringify functions, so your data never leaves your device. It handles arbitrarily large JSON as long as your browser has memory.

Frequently asked questions

How do I format or beautify JSON?
Paste your JSON into the text area and click Format. The tool parses and re-outputs it with proper indentation and line breaks. If the JSON is invalid, it shows the error message instead.
Why is my JSON invalid?
Common causes: missing commas between items, trailing commas after the last item, single quotes instead of double quotes, or unquoted keys. The error message tells you the position of the problem.
Can I change the indentation?
Yes. Adjust the indent size (2, 4, or a tab) and the formatter re-outputs the JSON with that spacing. The default is 2 spaces.
Is my JSON sent to a server?
No. All formatting and validation happens in your browser using the built-in JSON parser. Your data is never uploaded, so it is safe for sensitive configuration files.