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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.

✓ Valid JSON.

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.

Can it handle very large JSON files?

The tool runs in your browser, so the practical limit depends on available memory. For files over 10 MB, a command-line tool like jq is more reliable.

Does it support JSON5 or JSONC with comments?

No, this tool strictly parses JSON per RFC 8259. JSON5 and JSONC allow comments and unquoted keys that standard JSON forbids.

Sources & references

External references open in a new tab. We are independent and not affiliated with these organizations.

  • ✓ 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.

Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.

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