JSON Formatter & Validator
Format, validate, and beautify JSON instantly. Professional tool trusted by developers worldwide for API debugging and data formatting.
JSON Formatter & Validator
Format, validate, and beautify JSON data with syntax highlighting. Detect errors, format for readability, or minify for production.
📥 Input JSON
📤 Formatted Output
No output yet
Enter JSON and click "Format JSON" to see results
Features & Benefits
Beautiful Formatting
Auto-indent and beautify JSON for better readability and debugging.
Instant Validation
Real-time error detection with detailed error messages and line numbers.
Minification
Compress JSON for production use, reducing file size and bandwidth.
Easy Copy
One-click copying for seamless integration into your workflow.
Privacy First
All processing happens locally - your data never leaves your browser.
Mobile Friendly
Works perfectly on desktop, tablet, and mobile devices.
Common Use Cases
🔧 API Development
- • Validate API responses and requests
- • Format JSON for documentation
- • Debug malformed JSON data
- • Test JSON payloads
📊 Data Processing
- • Clean and format data exports
- • Validate configuration files
- • Prepare data for databases
- • Process log files
Complete JSON Guide: Syntax, Validation, and Best Practices
📚 What is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format. Despite its name, JSON is language-independent and used across virtually all modern programming languages.
Why Use JSON?
- • Human-readable: Easy to read and write for developers
- • Lightweight: Minimal syntax reduces data transmission costs
- • Universal support: Supported by all modern programming languages
- • Web-native: Perfect for REST APIs and web applications
- • Structured: Supports complex nested data structures
Common Use Cases
API responses, configuration files, data storage, message passing between services, AJAX requests, NoSQL databases, and mobile app data exchange.
🎯 JSON Syntax Rules
Basic Syntax Requirements
- • Data is in name/value pairs
- • Data is separated by commas
- • Curly braces hold objects
- • Square brackets [] hold arrays
- • Strings must use double quotes
- • No trailing commas allowed
- • No comments allowed in JSON
Data Types Supported
JSON vs Other Data Formats: When to Use What
📄 JSON vs XML
- • 50-70% smaller file size
- • Faster parsing
- • Native JavaScript support
- • More readable syntax
- • Supports attributes
- • Schema validation (XSD)
- • Namespace support
- • Better for documents
⚡ JSON vs YAML
- • Faster parsing/generation
- • Universal support
- • Stricter syntax
- • Better for APIs
- • More human-readable
- • Supports comments
- • Multi-line strings
- • Better for configuration
🚀 JSON vs CSV
- • Supports nested structures
- • Mixed data types
- • Self-describing
- • Flexible schema
- • Smaller file size
- • Excel compatibility
- • Simple tabular data
- • Faster processing
JSON Best Practices and Common Pitfalls
✅ Best Practices
🏗️ Structure Design
- • Use camelCase for property names
- • Keep objects flat when possible
- • Use arrays for lists of similar items
- • Include version information for APIs
- • Use consistent naming conventions
🔒 Security Practices
- • Always validate JSON input
- • Use JSON.parse() safely with try-catch
- • Sanitize data before processing
- • Limit JSON payload size
- • Don't include sensitive data in logs
⚡ Performance Tips
- • Minimize data transmission with compression
- • Use appropriate data types
- • Avoid deeply nested structures
- • Consider pagination for large datasets
- • Use streaming for large JSON files
🚫 Common Pitfalls
💥 Syntax Errors
- • Using single quotes instead of double
- • Trailing commas after last element
- • Missing quotes around property names
- • Including JavaScript comments
- • Using undefined or functions
🐛 Logic Errors
- • Mixing data types inconsistently
- • Creating circular references
- • Not handling null values properly
- • Assuming properties always exist
- • Not validating nested structures
🔧 Design Issues
- • Over-nesting data structures
- • Inconsistent property naming
- • Including redundant information
- • Not considering API evolution
- • Missing error handling patterns
JSON in Modern Web Development
🌐 REST APIs
JSON is the standard format for REST API communication, used for both request and response bodies.
📦 Package Management
Package.json files define Node.js project dependencies, scripts, and metadata using JSON format.
"name": "my-app",
"version": "1.0.0",
"dependencies": {"react": "^18.0.0"}
}
⚙️ Configuration Files
Many tools use JSON for configuration: tsconfig.json, .eslintrc.json, settings files.
{
"compilerOptions": {
"target": "ES2020"
}
}
💾 Data Storage
NoSQL databases like MongoDB store documents in JSON-like format (BSON). localStorage also uses JSON.
JSON.stringify({"id": 1, "name": "John"}))
🔄 AJAX Requests
Modern JavaScript uses JSON for asynchronous data exchange with servers via fetch API.
.then(response => response.json())
.then(data => console.log(data))
📱 Mobile Development
Mobile apps use JSON for API communication, local storage, and configuration across iOS, Android, and React Native.
await AsyncStorage.setItem(
'userData', JSON.stringify(user))
Advanced JSON Concepts and Tools
🔍 JSON Schema Validation
JSON Schema provides a powerful way to validate the structure, data types, and constraints of JSON documents.
Schema Benefits
- • Validate API requests/responses
- • Generate documentation automatically
- • Ensure data consistency
- • Provide IDE autocomplete support
- • Enable form generation from schemas
Example Schema
{
"type": "object",
"properties": {
"name": {"type": "string", "minLength": 1},
"age": {"type": "integer", "minimum": 0},
"email": {"type": "string", "format": "email"}
},
"required": ["name", "email"]
}🧮 JSON Processing Tools
JSONPath
Query JSON documents using XPath-like syntax:
$.products[?(@.price < 100)] // Cheap products
JQ Command Line
Powerful command-line JSON processor:
JSON Patch
Standard format for describing changes to JSON documents:
Frequently Asked Questions
Q: What's the difference between JSON.parse() and eval()?
A: JSON.parse() is safer as it only parses valid JSON and won't execute code. eval() can execute any JavaScript, making it a security risk. Always use JSON.parse() for JSON data and handle parsing errors with try-catch blocks.
Q: Can JSON contain comments?
A: No, standard JSON doesn't support comments. However, some parsers support JSON with comments (JSONC), and tools like JSON5 extend JSON to include comments, trailing commas, and other JavaScript-like features.
Q: How do I handle large JSON files efficiently?
A: For large files, use streaming parsers instead of loading the entire file into memory. Consider pagination for APIs, compression (gzip), and tools like JSONStream for Node.js or streaming fetch responses in browsers.
Q: Why do I get 'unexpected token' errors?
A: Common causes include trailing commas, single quotes instead of double quotes, missing quotes around property names, or trying to parse HTML/text as JSON. Use a JSON validator to identify the exact syntax error location.
Q: How do I handle dates in JSON?
A: JSON doesn't have a native date type. Use ISO 8601 string format (2023-12-25T10:30:00Z) for dates, or Unix timestamps for simple cases. Parse these back to Date objects in your application code.
Q: Should I minify JSON for production?
A: Yes, for API responses and large data files. Minifying removes whitespace, reducing bandwidth usage. However, use HTTP compression (gzip/brotli) which is more effective. Keep formatted JSON for development and debugging purposes.
Q: How do I validate JSON against a schema?
A: Use JSON Schema libraries like Ajv (JavaScript), jsonschema (Python), or built-in validation in many frameworks. Define your schema once and validate both client and server-side for consistency.
Q: What's the maximum size limit for JSON?
A: There's no official size limit, but practical limits include memory constraints, server payload limits (often 1-50MB), and browser limits. For large datasets, consider pagination, streaming, or alternative formats like Protocol Buffers.