Format & Validate
JSON Online
Instantly format, minify, and validate JSON with error detection. Works entirely in your browser — no data sent to servers.
Formatted JSON will appear here...Frequently Asked Questions
What is a JSON formatter?
A JSON formatter takes compressed or hard-to-read JSON text and formats it with proper indentation and line breaks for readability.
How do I validate JSON?
Click the "Validate" button to check if your JSON is valid. If there are errors, the exact error message will be displayed.
Which indent size should I choose?
2 spaces is compact and widely used. 4 spaces is more readable. Choose based on your team's coding standards.
What is JSON minification?
JSON minification removes all whitespace and newlines to minimize file size. It is commonly used for API responses and data transfer.
Master JSON Formatting & Validation
The complete guide to JSON structure, formatting, validation, and modern best practices.
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. It is the standard format for Web APIs, configuration files, and NoSQL databases. Originally derived from JavaScript, it is now supported by virtually every programming language.
JSON's 6 Data Types
- String: "hello" (double quotes required)
- Number: 42, 3.14, -100 (integers and floats)
- Boolean: true or false (lowercase only)
- null: null (explicitly no value)
- Object: {"key": value} key-value pairs
- Array: [1, 2, "three"] (ordered list)
JSON vs XML
Compared to XML, JSON is smaller, faster to parse, and more JavaScript-compatible. In REST API benchmarks, JSON averages 10-20% smaller file size and processes up to 3x faster than equivalent XML data.
JSON Structure Example
{
"user": {
"name": "Alice",
"age": 30,
"active": true,
"scores": [95, 87, 92],
"address": {
"city": "Tokyo",
"zip": "100-0001"
}
}
}JSON Formatting & Validation
Debugging a 5,000-line API response is painful, but formatted JSON is easy to read. This tool automatically applies indentation, line breaks, and consistent spacing, and pinpoints the exact location of syntax errors.
Common JSON Errors
- Trailing comma after last property (not allowed in JSON)
- Single quotes for strings (only double quotes allowed)
- Comments (JSON does not support // or /* */ comments)
- undefined values (use null instead)
- Unquoted keys ({name: "Alice"} is invalid)
JSON Schema Validation
JSON Schema defines the structure, data types, and required fields of JSON data. Libraries like Ajv (JavaScript) and jsonschema (Python) enable automatic validation before data enters your production environment.
REST API Responses
Primary format between frontend and backend
Config Files
package.json, tsconfig.json, .eslintrc.json etc.
NoSQL Databases
MongoDB and Firestore document format
Local Storage
Format for browser localStorage and sessionStorage