JSON Formatter

JSON Formatter illustration

Format, validate, and explore JSON with syntax highlighting and smart auto-repair.

lock Data never leaves your browser

Input

Try an Example:
data_object

Paste or type JSON in the input panel, then click Format

JSON Formatter Features

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Format & Beautify

Paste messy JSON and get perfectly indented, syntax-highlighted output. Auto spaces your arrays and arrays into objects cleanly.

build

Smart Auto-Repair

Paste "dirty" JSON with trailing commas, single quotes, JavaScript prefixes, or comments. The pipeline repairs them efficiently to pure JSON automatically.

account_tree

Tree View Parsing

Switch to an interactive tree view to explore deeply nested JSON structures via native HTML expansions without breaking lines.

Common Repaired Errors Reference

Error Type Example String Auto Fix
Trailing Comma {"a": 1, "b": 2,} Repaired
Single Quotes {'key': 'value'} Repaired
Unquoted Keys {name: "Alice"} Repaired
Embedded Comments {"a": 1} // comment here Repaired
JavaScript Prefix var x = {"val": 1}; Repaired

JSON Examples & Patterns

Standard patterns to help you structure your data correctly. Use these to test formatting and validation.

API Response 
{
  "status": "ok",
  "data": {
    "users": [
      { "id": 1, "name": "Alice Johnson",
        "email": "alice@example.com",
        "roles": ["admin", "editor"] },
      { "id": 2, "name": "Bob Smith", ... }
    ],
    "pagination": { "page": 1, "total": 2 }
  }
}
Package.json 
{
  "name": "my-app",
  "version": "2.1.0",
  "description": "A production web application",
  "scripts": {
    "dev": "vite", "build": "vite build",
    "test": "vitest", "lint": "eslint ."
  },
  "dependencies": { "fastify": "^5.1.0", ... }
}
Dirty JSON ⚠️ 
var apiData = {
  // User configuration
  'name': 'Test User',
  'settings': {
    'theme': 'dark',
    'notifications': true,
    'tags': ['important', 'starred',],
  },
}
Nested Config 
{
  "app": {
    "server": {
      "host": "0.0.0.0", "port": 3000,
      "ssl": { "enabled": true,
        "cert": "/etc/ssl/cert.pem" }
    },
    "database": {
      "primary": { "host": "db.example.com",
        "pool": { "min": 2, "max": 10 } },
      "replica": { ... }
    }
  },
  "logging": { "level": "info", ... }
}
Contains Errors ✕ 
{
  "users": [
    {"name": "Alice", "age": 30},
    {"name": "Bob", "age" 25}
  "total": 2
}

Frequently Asked Questions

How do I format JSON online? expand_more
Paste your JSON into the input field above and click Format. The tool will instantly beautify your JSON with proper indentation and syntax highlighting. You can choose between 2-space, 4-space, or tab indentation using the dropdown.
Is my JSON data safe? expand_more
Yes — your data never leaves your browser. All formatting, validation, and auto-repair happens 100% client-side using JavaScript. No data is sent to any server. You can verify this by disconnecting from the internet and using the tool — it works completely offline.
What is the difference between JSON and a JavaScript object? expand_more
JSON is a strict text format: all keys must be double-quoted strings, values cannot include undefined or functions, and trailing commas are not allowed. JavaScript objects are more permissive — they allow unquoted keys, single quotes, and trailing commas. This tool can auto-repair JavaScript-style objects into valid JSON.