JSON formatter and validator

JSON validation

JSON is valid

{
  "project": "UniTools",
  "version": 1,
  "active": true
}

Readable output, or a straight answer about what is wrong

Paste raw JSON to indent it readably, or find out exactly where it breaks. Runs in your browser, so payloads never leave the machine.

API responses arrive as one unbroken line. Formatting adds the indentation that makes structure visible, which is usually all you need to spot the field that is missing.

When JSON is invalid, the message tells you where parsing stopped. The culprit is almost always a trailing comma or a single quote — both legal in JavaScript, neither legal in JSON.

What this calculator shows

Indented, readable JSON with consistent nesting
A validation error pointing at the position that failed
Minified output when you need to shrink a payload back down

What to keep in mind

Everything runs locally in the browser; nothing is uploaded.
Strict JSON rules apply — comments and trailing commas are rejected, as any parser would reject them.

FAQs

Why is my JSON invalid when it looks fine?

Usually a trailing comma after the last item, single quotes instead of double, or an unquoted key. JavaScript object literals allow all three; JSON allows none.

Is it safe to paste production data here?

The parsing happens in your browser and nothing is sent anywhere. That said, treat any browser tab with the caution your data policy requires.

Can JSON contain comments?

No. The specification has no comment syntax. JSONC and JSON5 add them, but standard parsers will reject those files.

What is the point of minifying?

Whitespace is pure payload over the wire. Minified JSON is typically 10–30% smaller, which adds up on high-traffic APIs.

Worked example

A response worth reading

Input: {"user":{"id":42,"roles":["admin","editor"]}}

Output: Nested object across seven indented lines

Note: One line becomes a shape you can scan. With fifty fields instead of three, that difference stops being cosmetic.

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JSON formatter and validator

JSON validation

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