Is my JSON data secure?

Yes. FmtDev processes everything locally in your browser. Your data never leaves your machine.

Can I format invalid JSON?

No, the tool requires a valid JSON structure. If there are errors, they will be highlighted for you to fix.

Offline JSON Formatter & Beautifier (No Server Logs)

FmtDev Offline JSON Formatter & Beautifier is a free, browser-based tool that format, beautify, and validate JSON instantly offline. Find out how to fix JSON syntax errors with no server logs. It runs entirely on your device with zero data transmission, making it safe for proprietary code and sensitive content.

JSON Validation Guides

Why the JSON standard (RFC 8259) does not allow comments
Learn why your parser is throwing an unexpected token error and how to use JSONC instead.

Convert JSON to Code

Python Go Rust TypeScript C#Java Swift Kotlin Dart C++