About This Tool
Working with minified or poorly formatted JSON is a developer's daily frustration. API responses arrive as single-line walls of text impossible to scan. Config files get corrupted by careless edits that introduce invisible syntax errors. Log outputs blend together into unreadable chaos that takes forever to debug. Copy-pasting JSON between systems often strips formatting entirely, leaving you with an unreadable mess. This JSON formatter instantly transforms messy JSON into clean, properly indented code that's easy to read and understand. Choose your preferred indentation style (2 or 4 spaces), and the tool validates your JSON syntax in real-time, catching missing brackets, trailing commas, and other common errors before they cause runtime failures. Need to reduce file size? Switch to minify mode to strip all whitespace for production use. The interactive tree view lets you explore complex nested structures visually, making it easy to navigate deeply nested objects and arrays without getting lost in brackets.
What is JSON?
JSON (JavaScript Object Notation) is the universal standard for data exchange on the web. Invented by Douglas Crockford in the early 2000s, it has become the backbone of modern web development.
You'll encounter JSON in:
- REST APIs: Nearly every web API returns JSON responses
- Configuration files: package.json, tsconfig.json, .eslintrc
- Databases: MongoDB, CouchDB, and NoSQL databases store JSON documents
- Local storage: Web apps store data as JSON strings
Properly formatted JSON is easier to read, debug, and maintain. This tool helps you beautify compressed JSON from APIs, validate JSON syntax before using it, and minify JSON for smaller file sizes in production.
Understanding JSON Syntax Rules
JSON is strict about syntax. Here are the rules that trip up most developers:
- Keys must be double-quoted:
{"name": "John"}is valid,{name: "John"}is not - Strings must use double quotes:
"hello"works,'hello'fails - No trailing commas:
{"a": 1, "b": 2,}is invalid - No comments allowed: Unlike JavaScript, JSON doesn't support // or /* */
- Numbers can't have leading zeros:
007is invalid, use7
When this tool reports "Invalid JSON," check these common issues first. The error message will point you to the exact line and character where parsing failed.
When to Use 2-Space vs 4-Space Indent
Indentation is about readability and file size. Here's when to use each:
2 spaces (recommended for web development):
- Smaller file sizes - saves bandwidth on API responses
- Standard in JavaScript/TypeScript projects (matches popular style guides)
- Better for deeply nested structures - less horizontal scrolling
- Used by npm, Prettier, and most modern tools
4 spaces (recommended for configuration files):
- More readable for simple, shallow structures
- Common in Python and Java ecosystems
- Better for non-developers reviewing configs
- Matches traditional code formatting standards
Tab character: Some teams prefer tabs for accessibility - users can set their preferred tab width in their editor.
Formatting vs Minifying: When to Use Each
Format/Beautify when you need to:
- Debug API responses or find specific values
- Edit configuration files manually
- Review data in pull requests or code reviews
- Document examples in README files
Minify when you need to:
- Reduce payload size for API responses
- Store JSON in databases or localStorage efficiently
- Embed JSON in HTML or JavaScript files
- Optimize for production deployment
A typical JSON payload can be reduced by 20-40% through minification by removing whitespace and newlines.
Security Considerations for JSON Data
JSON is often used to transmit sensitive data between clients and servers, so security must be a priority:
- Never trust unvalidated JSON: Always validate and sanitize JSON input on the server before processing it. Malformed or malicious payloads can exploit parsing vulnerabilities.
- Avoid eval() for parsing: Use
JSON.parse()instead ofeval(). The eval function executes arbitrary JavaScript code, making it a severe injection risk. - Sensitive data exposure: Avoid logging or displaying raw JSON that may contain personal data, API keys, or tokens. Redact sensitive fields before outputting.
- Content-Type headers: Ensure your server sends JSON with the correct
Content-Type: application/jsonheader to prevent MIME sniffing attacks. - CORS and JSON: When serving JSON APIs, configure Cross-Origin Resource Sharing (CORS) headers correctly to prevent unauthorized access from other domains.
This tool processes your JSON entirely on your device, so no data is ever sent to an external server. For production systems, combine JSON validation with schema enforcement using tools like JSON Schema or Zod.