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JSON Formatter & Validator — Free Online Tool

Format, minify and validate JSON. Works entirely in your browser. Your files never leave your device.

Open JSON Formatter Free
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What is JSON Formatter?

JSON Formatter and Validator is a free browser-based developer tool that pretty-prints minified JSON, validates syntax and helps debug malformed JSON data. Paste raw or minified JSON and click Format to instantly indent it with proper nesting, making the structure readable without writing any code.

JSON (JavaScript Object Notation) is the dominant data interchange format used by REST APIs, configuration files, databases and web applications. Minified JSON removes all whitespace to reduce file size, but makes it unreadable to humans during development and debugging. The formatter adds consistent two-space indentation, line breaks and color-coded key/value pairs.

The validator checks for common JSON errors: unquoted keys, trailing commas (allowed in JavaScript but not in JSON), mismatched brackets, invalid escape sequences in strings, and incorrect value types. When an error is found, the exact line and character position is reported so you can fix it immediately. The Minify function compresses formatted JSON back to a single line for production use or API requests.

⚡
Instant results
No server processing or wait
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100% private
Files stay on your device
💰
Always free
No subscription or fees
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Mobile ready
Works on any device

How to use JSON Formatter

  1. Paste your JSON data into the input box — minified or raw
  2. Click Format to instantly pretty-print with proper indentation
  3. Use Validate to check for syntax errors — exact error location is shown
  4. Copy the formatted JSON or use Minify to compress it back

Why use OnlineToolsPlus?

OnlineToolsPlus processes everything locally in your browser. Your files, text and data never leave your device, which eliminates server-side privacy risks. With 200+ free tools covering PDF, image, AI writing, developer utilities, calculators, SEO, color tools and more, there is no need to juggle multiple subscriptions or install software.

Frequently asked questions

What is the difference between format and minify?
Format adds indentation and line breaks to make JSON readable. Minify removes all whitespace to produce the smallest possible file for production use or transmission.
What is JSON validation?
Validation checks that the JSON follows correct syntax. Common errors include trailing commas, single quotes instead of double quotes, missing commas between items, and unescaped special characters.
Can I sort JSON keys alphabetically?
Yes. Sorting keys can make large JSON objects easier to scan and compare.
What is the maximum size of JSON I can process?
Everything runs in the browser. Very large JSON files may be slow but there is no hard limit.
Can I collapse and expand nested objects?
Yes. The tree view allows you to fold and unfold nested objects and arrays to navigate complex structures.
Does it work offline?
Yes.

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Last updated: April 11, 2026

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