Free Online JSON Formatter & Validator
Format, beautify, validate, fix, and minify JSON data instantly. Our JSON formatter parses your data in real time, highlights syntax errors with clear messages, and outputs cleanly indented JSON with color syntax highlighting. Switch between code view and tree view to navigate complex data structures. Upload JSON files directly or paste from clipboard. Everything runs in your browser — your data is never sent to any server.
How to Use
Paste or upload
Paste raw JSON from an API response, config file, or upload a .json file directly.
Format or fix
Click Format to beautify, Minify to compress, or Fix to auto-repair common JSON errors.
Explore
Switch between Code view with syntax highlighting and Tree view with collapsible nodes.
Export
Copy to clipboard or download as a .json file. Validation errors are shown with clear messages.
Features
Real-time validation
Instantly validates JSON as you type with descriptive error messages and line highlights
Syntax highlighting
Color-coded output: strings in green, numbers in blue, booleans in purple, null in red
Tree view
Collapsible tree visualization of your JSON structure. Expand and collapse objects and arrays
Fix JSON
Auto-repair common errors: remove trailing commas, fix quotes, strip comments, quote unquoted keys
File upload
Upload .json files directly from your computer instead of copy-pasting
Line numbers
Both input and output show line numbers for easy reference and debugging
Flexible indentation
Choose between 2, 4, or 8 spaces. Switch between formatted and minified views
100% private
Everything runs in your browser. Your JSON data never leaves your device
What is JSON?
JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write and easy for machines to parse and generate. It's the most common format for API responses, configuration files, and data storage in modern web development.
JSON supports six data types: strings, numbers, booleans, null, arrays, and objects. Despite its name, JSON is language-independent and is used across virtually every programming language including JavaScript, Python, Java, C#, Go, Ruby, PHP, and many more.
Common JSON Errors
| Error | Cause | Fix |
|---|---|---|
| Unexpected token | Trailing comma, single quotes, or unquoted keys | Use double quotes, remove trailing commas. Click "Fix" to auto-repair |
| Unexpected end of input | Missing closing bracket or brace | Ensure every { has a } and every [ has a ] |
| Expected double-quoted property name | Keys without quotes or with single quotes | Wrap all keys in double quotes. Click "Fix" to auto-repair |
| Unexpected number | Leading zeros on numbers | Remove leading zeros (use 0.5 not 00.5) |
| Bad control character | Unescaped newlines or tabs in strings | Use \n for newlines, \t for tabs |
JSON Formatting vs Minification
| Feature | Formatted | Minified |
|---|---|---|
| Readability | Easy to read and edit | Hard to read |
| File size | Larger (whitespace added) | Smallest possible |
| Best for | Development, debugging, config files | Production, API responses, storage |
| Whitespace | Indentation + newlines | None |
Frequently Asked Questions
Yes, completely free with no limits. Format, validate, fix, and minify as much JSON as you want. No account needed.
Yes. Everything runs in your browser using JavaScript. Your JSON data never leaves your device — nothing is uploaded to any server.
Fix attempts to auto-repair common JSON errors: it removes trailing commas, replaces single quotes with double quotes, strips comments, and adds quotes to unquoted property names. It won’t fix every error but handles the most common mistakes.
Tree view shows your JSON as a collapsible hierarchy. Click any object or array to expand/collapse it. This is useful for navigating large, deeply nested JSON structures.
Yes. Click the Upload button to select a .json or .txt file from your computer. The file contents will be loaded into the editor automatically.
There’s no hard limit, but very large files (over 10MB) may slow down your browser since everything is processed client-side. For typical API responses and config files, performance is instant.
2 spaces is the most common in JavaScript/TypeScript. 4 spaces is standard in Python and Java. Pick whatever matches your project’s style guide.
Format adds indentation and newlines for readability. Minify removes all whitespace for the smallest file size. Use formatted for development, minified for production.
Common mistakes: trailing commas, single quotes instead of double quotes, unquoted keys, comments (not supported in JSON), and missing brackets. Try the Fix button to auto-repair, or check the error message for details.
Absolutely. Paste raw JSON from any API response and it’ll be instantly formatted with syntax highlighting. Use tree view to navigate complex nested responses.