JSON Formatter & Validator

While JSON syntax is based on JavaScript object notation, they're not identical. JSON requires double quotes for all keys and string values, doesn't support trailing commas, cannot contain functions or undefined values, and doesn't allow comments. JavaScript objects are more flexible, allowing single quotes, unquoted keys, trailing commas, functions, and comments. Think of JSON as a strict subset of JavaScript object notation designed specifically for data exchange.

The most common JSON errors are: trailing commas after the last item, using single quotes instead of double quotes, forgetting to quote object keys, missing commas between items, unclosed brackets or braces, and invalid escape sequences. Our formatter provides detailed error messages with line and column numbers to help you quickly identify and fix these issues. Copy your JSON into the formatter to see exactly what needs to be corrected.

No, the JSON specification doesn't support comments. If you need documentation within your JSON data, you can add a special key like "_comment" or "description" with string values. Some tools support JSON5 or JSONC (JSON with Comments) which allow comments, but these are not standard JSON and won't work with most JSON parsers. For configuration files that need comments, consider using YAML, TOML, or your language's native configuration format.

JSON strings must escape certain special characters using backslash: \\ for backslash, \" for double quote, \n for newline, \r for carriage return, \t for tab, \b for backspace, \f for form feed, and \uXXXX for Unicode characters. For example, to include a quote in a string, use "He said \"Hello\"". Proper escaping ensures your JSON remains valid and displays correctly when parsed.

Yes, completely safe. All JSON formatting, validation, and processing happens entirely in your browser using JavaScript. No data is ever transmitted to our servers, stored in databases, or shared with third parties. You can even disconnect from the internet after loading the page and the formatter will continue to work. This makes it safe to format sensitive data like API keys, configuration secrets, or proprietary data structures.

Yes, for APIs and data transfer, minified JSON reduces file size by 20-30%, improving load times and reducing bandwidth costs. However, keep formatted versions for development and debugging. Use minification as part of your build process, not manually. For configuration files on servers, formatting matters less than correctness, so choose what's more maintainable for your team.

JSON supports six data types: objects, arrays, strings, numbers, booleans, and null. It cannot directly represent dates (use ISO 8601 strings), functions (not serializable), undefined (use null), circular references (will cause errors), NaN or Infinity (use null or strings), or binary data (use Base64 encoding). For complex data types, you'll need to serialize them to JSON-compatible formats and deserialize them on the receiving end.

This depends on your project's coding standards. 2 spaces is compact and widely used in modern web development (default for Prettier). 4 spaces provides better visual separation and is common in enterprise projects. 3 spaces is less common. Choose what your team uses consistently across your codebase. Most importantly, be consistent—mixing indentation styles causes version control conflicts and reduces readability.

Our formatter handles reasonably large files (several megabytes), but very large files (10MB+) may slow down or crash your browser. For extremely large JSON files, consider: streaming parsers that process data in chunks, command-line tools like jq for large-scale processing, or database imports instead of in-browser formatting. For web applications, paginate or chunk large JSON responses instead of sending everything at once.

This is a browser-based tool designed for manual use. For programmatic JSON formatting, use your programming language's built-in functions: JSON.stringify() in JavaScript, json.dumps() in Python, json_encode() in PHP, or JSON.Marshal() in Go. For command-line formatting, use jq (Unix/Linux/Mac) or integrate Prettier into your build process for automated formatting across your entire project.