JSON Formatter & Validator

Format, validate, and beautify JSON data. Free online JSON formatter with syntax highlighting and error detection.

Input

Output

Advanced JSON Validation and Formatting

Data integrity starts with valid syntax. Our JSON formatter doesn't just beautify code; it performs a deep structural audit of your payloads. By running 100% in your browser, it ensures that sensitive API keys, user data, and configurations are never transmitted to a third-party server.

Instant Error Detection

Get real-time feedback on trailing commas, missing quotes, and mismatched brackets as you type.

Why Format Matters

✓
Readability for collaborative code reviews.
✓
Reduced debugging time for nested API responses.
✓
Local-only execution for maximum security.

Format and validate JSON without changing its data

Use the formatter to make compact JSON readable, locate syntax failures, and inspect nested arrays and objects. Formatting changes whitespace only; it does not rename keys or coerce values.

Example input

{"user":{"id":42,"roles":["editor","reviewer"]},"active":true}

Expected output

{
  "user": {
    "id": 42,
    "roles": ["editor", "reviewer"]
  },
  "active": true
}

Behavior

Accepts JSON objects, arrays, strings, numbers, booleans, and null.
Preserves Unicode text and the order in which object keys were supplied.
Tree view is intended for inspection; text view is the exact formatted result to copy.

Limits and edge cases

Comments and trailing commas are not valid JSON.
Very deeply nested or extremely large documents remain limited by browser memory.
Formatting validates syntax, not whether values match an application schema.

Processing note: tool input stays in the browser. Readme.now analytics records page usage, not the payload you paste or the generated output.

Authoritative reference: ECMA-404: The JSON data interchange syntax