JSON (JavaScript Object Notation) has taken over the world. It is the backbone of REST APIs, configuration files, and NoSQL databases like MongoDB. Its simplicity is its strength—readable by humans, parsable by machines.

However, raw JSON usually comes in two frustrating forms: a massive, single-line compressed string (impossible to read) or broken code with a missing comma (impossible to parse). The JSON Formatter & Validator solves both problems.

What This Tool Does

  1. Beautify: Turns {"id":1,"name":"foo"} into a multi-line, indented object.
  2. Validate: Checks for syntax errors (like trailing commas or unquoted keys) and points to the exact line number.
  3. Minify: Compresses whitespace to create the smallest valid JSON string for transmission.

JSON vs XML vs YAML

Why is JSON the most popular?

  • Simplicity: JSON handles Objects, Arrays, Strings, Numbers, Booleans, and Null. That's it. No complicated attributes (XML) or significant whitespace (YAML).
  • Wait...: Actually, comments are NOT supported in standard JSON (RFC 8259). This is a common point of confusion. If you need comments, consider YAML or JSON5.

Common JSON Syntax Errors

Our validator catches these common mistakes:

1. Trailing Commas

{
  "name": "John",
} ❌ Error!

JSON does not allow a comma after the last item in an object or array.

2. Single Quotes

{
  'name': 'John' ❌ Error!
}

JSON strings and keys must be wrapped in double quotes ("). Single quotes are valid in JavaScript, but not in JSON.

3. Unquoted Keys

{
  name: "John" ❌ Error!
}

Keys must always be strings.

Data Structure Visualization

When you have a deeply nested JSON file (like a 5MB API response), a text editor isn't enough. Our tool provides a collapsible tree view:

  • Start/End brackets are matched.
  • You can collapse large arrays (`items: [ ... 100 items ... ]`) to focus on relevant data.
  • Color-coding distinguishes numbers (blue), strings (green), and booleans (purple).

RFC 8259 Compliance

This tool adheres strictly to RFC 8259. This ensures that any JSON you validate here will work correctly in any compliant parser (Python's json, Java's Jackson, Node.js, etc.).

Have strict rules? Use our JSON Schema Validator to check data against a defined schema.