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U UtilHQ

JSON Formatter & Validator

Format messy JSON into readable, properly indented code. Validate JSON syntax and minify for production use. Whether you're debugging API responses, editing configuration files, or preparing data for storage, this free tool makes JSON easy to work with.

100% Free
No Data Stored
Instant Results

Pro Tip: Use 2-space indent for web projects (saves bandwidth) and 4-space for config files (better readability).

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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: 007 is invalid, use 7

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.

Frequently Asked Questions

Why is my JSON invalid?
Common JSON errors include: trailing commas after the last item, single quotes instead of double quotes, unquoted property keys, missing brackets or braces, comments (not allowed in JSON), and special characters that need escaping. The error message shows the exact position where parsing failed - look for issues just before that point.
Is my data sent to a server?
No. This tool runs entirely in your browser using JavaScript. Your JSON never leaves your computer - all processing happens locally. You can even use this tool offline after the page loads. We never see, store, or transmit your data.
What is the maximum JSON size this tool can handle?
Browser-based tools can typically handle JSON files up to 50-100MB depending on your device's memory. For larger files (hundreds of MB or GB), use command-line tools like jq, or process the JSON in chunks using streaming parsers.
How do I format JSON in VS Code?
In VS Code, select your JSON and press Shift+Alt+F (Windows) or Shift+Option+F (Mac) to format. For better results, install the Prettier extension and set it as your default formatter. You can also use this online tool when you need quick formatting without opening an editor.
Can I validate JSON against a schema?
This tool validates that your JSON is syntactically correct. For schema validation (checking that specific fields exist with correct types), you would need a JSON Schema validator. Popular options include ajv for JavaScript or jsonschema for Python.