JSON Formatter — Free Online Tool
Pretty-print and validate JSON with clear, line-aware error messages.
About JSON Formatter
The JSON Formatter beautifies and validates JSON directly in your browser. Paste minified or poorly indented JSON and instantly get clean, readable output with proper nesting, making it far easier to debug API responses, configuration files, and data payloads.
Beyond formatting, the tool acts as a strict validator. If your JSON contains a syntax error, it reports the exact problem so you can correct it fast. Everything runs locally, so even sensitive data stays private on your machine.
How to Use JSON Formatter
- Paste or type your JSON into the input box.
- Click 'Format' to pretty-print it with clean 2-space indentation.
- Click 'Validate' to check the syntax without reformatting.
- Use 'Copy Result' to copy the formatted JSON to your clipboard.
Key Features
Pretty-print JSON with clean, consistent 2-space indentation
Instant syntax validation with clear, line-aware error messages
100% client-side processing - your JSON never leaves the browser
One-click copy of the formatted output
Works with deeply nested objects and large arrays
Frequently Asked Questions
What does a JSON formatter do?
A JSON formatter takes minified or messy JSON and reformats it with consistent indentation and line breaks, making the structure easy to read. It also validates the syntax and reports the exact error if the JSON is invalid.
Is my JSON data sent to a server?
No. All formatting and validation happen entirely in your browser using JavaScript. Your JSON never leaves your device, so it is safe to use with confidential data.
What indentation does the formatter use?
The tool pretty-prints your JSON using standard 2-space indentation, which is the most common convention for readable JSON in APIs and config files.
Why is my JSON marked invalid?
Common causes include trailing commas, single quotes instead of double quotes, missing brackets, or unquoted keys. The error message shows the position so you can fix it quickly.