HIFreeTools

Free JSON Formatter & Validator

Paste JSON to pretty-print it, validate it, or minify it. Errors are reported with a clear message so you can find the problem fast.

Quick answer

A JSON formatter parses your JSON and re-prints it with consistent indentation so it’s easy to read, while validating that the syntax is correct. Minifying does the reverse — it removes whitespace to make the smallest valid JSON.

Formula & method

Your text is parsed with the browser’s built-in JSON parser. If it’s valid, it’s re-serialized with two-space indentation (formatting) or with no whitespace (minifying). If it’s invalid, the parser’s error message is shown so you can locate the issue. Everything happens locally — your JSON is never sent to a server.

Examples

Example 1: Minified input
Input
{"name":"Ada","langs":["Ada","C"]}
Result
Pretty-printed over multiple lines with 2-space indents
Why
Formatting expands the object so structure is visible.
Example 2: Invalid JSON
Input
{"a": 1,}
Result
Error: trailing comma
Why
JSON doesn’t allow a comma before a closing brace.
Example 3: Minify
Input
A formatted 2 KB object
Result
Whitespace removed
Why
Minifying produces the smallest valid equivalent.

When to use this tool

  • Reading an API response that came back as one long line.
  • Checking whether a config or payload is valid JSON before using it.
  • Shrinking JSON for storage or transport by minifying it.

Common mistakes

  • Using single quotes. JSON requires double quotes around keys and string values.
  • Leaving a trailing comma after the last item — valid in JavaScript, invalid in JSON.
  • Pasting a JavaScript object or JSON5, which allow comments and unquoted keys that strict JSON rejects.

Frequently asked questions

＋ What does formatting JSON do?

It re-prints valid JSON with consistent indentation and line breaks so the structure is easy to read. The data itself is unchanged.

＋ How does validation work?

The tool tries to parse your text as JSON. If parsing fails, it shows the error so you can fix the syntax; if it succeeds, your JSON is valid.

＋ What is minifying?

Minifying removes all unnecessary whitespace to produce the smallest valid JSON — useful for reducing payload size.

＋ Is my JSON sent to a server?

No. Parsing and formatting run entirely in your browser, so sensitive payloads and tokens never leave your device.

＋ Why does it reject comments?

Standard JSON doesn’t support comments. Formats like JSON5 or JSONC do, but they aren’t valid strict JSON.

  • ✓ Free to use
  • ✓ No sign-up required
  • ✓ Runs entirely in your browser — nothing is uploaded.
  • ✓ Formula and method shown above
Last updated: How we calculateReport a correctionDisclaimer

Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.

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