Best Free Online JSON Formatter
Beautify, compress, validate, and tree-view JSON. All in your browser — 100% private, no data uploaded.
Key Features
Beautify & Validate
Format messy JSON in one click while automatically detecting syntax errors and locating the offending line.
Compressed Output
Strip whitespace and newlines to produce compact JSON, ideal for API transport and storage.
Error Location
On syntax errors, highlight the position and cause so you can fix issues quickly.
100% Local Processing
Everything runs in your browser. Your data never leaves your device.
How to Use
Paste JSON
Paste the JSON you want to format, or drag and drop a .json file directly.
Click Format
Click the Format button and the tool will beautify the layout and detect any syntax errors.
Copy or Download
Copy the result with one click or download it. Switch to compressed mode for a compact version.
Frequently Asked Questions
Is my JSON data uploaded to a server?
No. This JSON formatter runs entirely locally in your browser. Your data never leaves your device, so it is safe to process sensitive data.
How large a JSON file can I process?
Up to 10MB of JSON content, which covers the vast majority of development scenarios.
What happens when my JSON has a syntax error?
The tool points out the exact line number and cause so you can locate and fix the problem quickly, instead of just showing a failure.
Does it support JSON with comments?
Yes. The tool handles loose JSON with // comments or unquoted keys, useful for pasting content from config files or AI output.