ToolocoTooloco

JSON Formatter & Validator

Format, prettify and validate JSON online. Instantly beautify minified JSON with syntax highlighting.

Input JSON
Output

Formatted output will appear here

About this tool

JSON (JavaScript Object Notation) is the most widely used data interchange format in web development. It is used in REST APIs, configuration files, log outputs, and data storage. When JSON is minified (all whitespace removed) it becomes very difficult to read and debug. This formatter parses your JSON and re-formats it with proper indentation, making nested objects and arrays immediately readable. It also validates your JSON and highlights any syntax errors.

  • ✅ Free to use, no sign-up required
  • ✅ Files never leave your device
  • ✅ Instant conversion
  • ✅ Works on any browser and device

How it works

Your input is parsed using the browser's built-in JSON.parse() function, which validates the syntax and builds an internal object tree. If parsing succeeds, the object is serialized back to a string using JSON.stringify() with 2-space indentation. Any syntax error is caught and displayed with the relevant error message so you can locate and fix the problem.

Frequently Asked Questions

What is minified JSON and why would I need to format it?
Minified JSON has all whitespace, newlines, and indentation removed to reduce file size. While this is useful for transmission, it is nearly impossible to read by eye. Formatting ("pretty-printing") restores the structure to make debugging and inspection practical.
Can this tool validate whether my JSON is valid?
Yes — if your JSON has a syntax error (missing comma, mismatched brackets, unquoted keys), the tool will display the error message from the parser so you can locate and fix the problem.
Is my JSON data sent to a server?
No. All parsing and formatting happens inside your browser using JavaScript. Your JSON data never leaves your device, making this tool safe to use with sensitive or internal data.
What is the difference between JSON and JavaScript objects?
JSON is a text format that looks like JavaScript object syntax but has stricter rules: all keys must be double-quoted, trailing commas are not allowed, and undefined, NaN, and Infinity are not valid values. A JavaScript object is an in-memory data structure.

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