JSON Formatter & Validator
Paste JSON to format, validate, or minify — processed locally in your browser
Error
Valid JSON
Type
Size
Keys
Depth
About This Tool
- Format — Pretty-prints JSON with your chosen indentation for readability.
- Minify — Removes all whitespace to produce the smallest possible output.
- Validate — Checks syntax and reports the exact error location with structure stats.
- Local Processing — Your data never leaves the browser. Everything runs on your device.
- Large Payloads — Efficiently handles JSON files up to several megabytes.
What Is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data format used to store and exchange structured data. Invented by Douglas Crockford in the early 2000s, JSON has become the universal language of web APIs, configuration files, and data storage. Almost every modern programming language can parse and generate JSON natively.
JSON Syntax Rules
JSON must adhere to strict syntax rules. Common validation errors occur when these rules are broken:
- Keys must be strings in double quotes —
{"name": "value"}is valid;{name: "value"}is NOT - String values must use double quotes — single quotes are invalid in JSON (unlike JavaScript)
- No trailing commas —
{"a": 1,}is invalid JSON (though some parsers accept it) - No comments — JSON does not support
// commentsor/* block comments */ - Valid value types: string, number, boolean (
true/false), null, array, or object - Numbers: Cannot have leading zeros (
007is invalid), but can use scientific notation (1.5e10)
When to Format vs Minify vs Validate
- Format: Use when debugging, reviewing, or editing JSON. Pretty-printed JSON with indentation is much easier to read and understand. Ideal for inspecting API responses.
- Minify: Use before deploying JSON in production environments. Minified JSON removes all whitespace, reducing file size by 20–40% for typical payloads. This reduces bandwidth usage and speeds up data transfer for APIs.
- Validate: Use to quickly check if JSON is valid before using it in code. This tool also shows structure statistics (data type, key count, nesting depth) that help you understand unfamiliar JSON structures.
Common JSON Use Cases
- REST APIs: The vast majority of web APIs exchange data in JSON format — request bodies, responses, and error messages
- Configuration files: package.json (Node.js), tsconfig.json (TypeScript), .eslintrc (ESLint), extensions manifest files (Chrome, VSCode)
- Databases: MongoDB stores documents as BSON (Binary JSON); PostgreSQL has native JSON/JSONB column types; many NoSQL databases are fundamentally JSON-based
- State management: Redux, Vuex, localStorage, and sessionStorage all use JSON serialization for state persistence
- Data interchange: Exporting data between applications that don't share a database