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JSON formatter & validator

Pretty-print, validate, explore as tree, and generate TypeScript interfaces from JSON. Fully offline.

Indent
24 lines13 keys258 bytes
Formatted JSON
json
{
  "name": "SlapMyWeb",
  "version": "2.0",
  "features": [
    "SEO audit",
    "AI roast",
    "107 free tools"
  ],
  "pricing": {
    "free": 0,
    "pro": 9,
    "agency": 29
  },
  "active": true,
  "metadata": {
    "founded": 2024,
    "team": [
      {
        "name": "Atif",
        "role": "founder"
      }
    ]
  }
}

What is JSON Formatter & Validator?

A JSON formatter is a developer tool that takes raw, compact, or messy JSON data and restructures it with consistent indentation and line breaks so it becomes easy to read and debug. JSON (JavaScript Object Notation) is the most widely used data-interchange format on the web, powering REST APIs, configuration files, NoSQL databases, and more. When API responses arrive as a single compressed line, finding a specific key or spotting a missing comma becomes nearly impossible without formatting. Our free JSON formatter parses your input in real time, validates it against the JSON specification, and highlights syntax errors with clear messages. Choose between 2-space or 4-space indentation to match your project style. Explore nested data with the collapsible tree view, or generate TypeScript interfaces automatically. Everything runs entirely in your browser using the native JSON.parse engine, so your data never leaves your machine.

How to Use JSON Formatter & Validator

  1. 1

    Paste your JSON

    Copy raw or minified JSON from your API response, config file, or database export and paste it into the input area. The tool accepts any valid JSON including objects, arrays, and nested structures.

  2. 2

    Choose indentation

    Select 2-space or 4-space indentation using the toggle buttons. The output updates instantly as you switch between styles, so you can pick whichever matches your team's code convention.

  3. 3

    Explore with tree view

    Switch to Tree mode to explore your JSON as collapsible nodes. Click arrows to expand or collapse objects and arrays. Great for navigating deeply nested API responses.

  4. 4

    Generate TypeScript interfaces

    Switch to TypeScript mode to automatically generate type-safe interfaces from your JSON structure. Copy the output directly into your .ts files.

Features

  • Real-time pretty-printing with 2 or 4 space indentation
  • Collapsible tree view for exploring nested JSON structures
  • Automatic JSON to TypeScript interface generation
  • Line numbers toggle for referencing specific lines
  • One-click minification for compact output
  • Instant syntax validation with descriptive error messages
  • Stats display: line count, key count, byte size
  • Zero server calls — all processing in your browser

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Frequently Asked Questions

Is my JSON data sent to a server?+
No. The entire formatting and validation process runs in your browser using the native JSON.parse API. Your data never leaves your machine, making it safe for sensitive payloads like API keys or user data.
What JSON errors does the validator catch?+
The tool catches all JSON specification violations including missing commas, trailing commas, unquoted keys, single-quoted strings, mismatched brackets, and unexpected tokens. The error message pinpoints the character position where parsing failed.
How does the TypeScript interface generator work?+
It analyzes the structure of your JSON — detecting objects, arrays, strings, numbers, booleans, and nulls — and generates matching TypeScript interfaces. Nested objects get their own named interfaces, and arrays of objects generate item types automatically.
Can I format JSON with comments?+
Standard JSON does not allow comments. If your input contains JavaScript-style comments (// or /* */), the parser will report a syntax error. Remove comments first, or use a JSONC-aware tool for commented config files.
What is the difference between 2-space and 4-space indentation?+
Both produce valid formatted JSON. 2-space indentation is more compact and popular in JavaScript/TypeScript projects, while 4-space is common in Python ecosystems and some enterprise standards. Choose whichever your team prefers.
Is there a size limit for the JSON input?+
There is no artificial limit. The tool processes JSON in your browser memory, so it handles payloads of several megabytes without issues. For extremely large files (50MB+), performance depends on your device.