Free JSON Formatter & Validator
Paste JSON to format, validate, and explore. Syntax highlighting, error detection, and tree view. 100% private.
Output
Settings
Sort Keys Alphabetically
Theme
Follow site theme automatically
Quote style display
Double quotes (JSON standard)
Frequently Asked Questions
What is JSON?
JSON (JavaScript Object Notation) is a lightweight data format used to exchange data between a server and a web application. It is human-readable and widely used in APIs and configuration files.
How do I validate JSON?
Paste your JSON into the input field and click Format. If the JSON is valid, you will see the formatted output with syntax highlighting. If it is invalid, you will see an error message with the exact line and column where the problem is.
What does 'Unexpected token' mean?
This error means the JSON parser found a character it did not expect at that position. Common causes include missing commas, extra trailing commas, single quotes instead of double quotes, or unquoted keys.
What is the difference between JSON and JavaScript objects?
JSON is a text format with strict rules: keys must be double-quoted, no trailing commas, no comments, and no functions. JavaScript objects are more flexible but cannot be transmitted as text without converting to JSON first.
Can I format large JSON files?
Yes. This tool handles JSON files up to 5MB. For very large files, processing may take a moment. All formatting happens in your browser — no data is uploaded.
Is my JSON data private?
Yes. Everything runs locally in your browser. No data is sent to any server, stored, or logged. Your JSON never leaves your device.