ToolNestFree Online JSON Formatter & Validator
Validate, beautify, and minify JSON in seconds. Our free JSON formatter checks your JSON for syntax errors, pretty-prints it with indentation, or compresses it to a single line — everything developers need when working with APIs, configs, and data files.
✓ Free forever · ✓ No signup · ✓ Runs in your browser — your data never leaves your device.
How to Use the JSON Formatter
- Paste your JSON into the input box.
- Click 'Format / Beautify' to pretty-print it with 2-space indentation.
- Click 'Minify' to compress it to a single line for production use.
- If the JSON is invalid, you'll get the exact error message and position.
Why Use Our JSON Formatter?
- Real validation — uses the browser's JSON parser; error messages point to the problem.
- Beautify & minify — readable output for debugging, compact output for shipping.
- Handles large payloads — paste API responses of any reasonable size.
- Private — your data never leaves your browser, safe for sensitive payloads.
Frequently Asked Questions
What is JSON?
JSON (JavaScript Object Notation) is a lightweight text format for structured data, used by virtually every web API.
What does 'minify' mean?
Removing all unnecessary whitespace to make the JSON as small as possible — useful for production payloads and configs.
Why does my JSON fail validation?
Common causes: trailing commas, single quotes instead of double quotes, unquoted keys, or comments. The error message tells you where.
Can I format JSON with comments (JSONC)?
Standard JSON doesn't allow comments. Remove them first — the validator will flag their position.
Is my JSON data safe here?
Yes — formatting happens entirely in your browser; nothing is sent to any server.