About formatjson.app

formatjson.app is a free json formatter, json validator, and json beautifier that runs entirely in your browser. There's no server, no account, and no upload. Your JSON never leaves your device.

The tool was built for developers who want a fast, distraction-free way to format json and validate json without worrying about where their data goes. Paste your JSON, get clean output instantly — syntax highlighted, with error messages in plain English.

How it works

All processing uses native browser JavaScript APIs: JSON.parse for parsing and validation, and JSON.stringify for formatting and minification. There are no external libraries for JSON handling — just the same APIs your browser uses internally every day.

Features

• Real-time json formatter with 300ms debounce
• JSON validator with plain-English error messages
• JSON minifier (single-line output)
• Syntax highlighting (keys, strings, numbers, booleans, null)
• Configurable indent: 2 spaces, 4 spaces, or tab
• File upload by drag and drop
• Download formatted output as .json
• Dark mode with system preference detection
• Keyboard shortcut: Cmd/Ctrl+Shift+F to format

Free to use. Ad-supported. No signup required.