Dev Tools

JSON Formatter & Validator

Paste your JSON to format, validate, or minify it. Compare two JSON documents side by side.

Quick Answer

JSON (JavaScript Object Notation) is a lightweight data format that uses key-value pairs and arrays. Valid JSON requires double-quoted keys, no trailing commas, and no comments. Formatting (pretty-printing) adds indentation to make JSON readable, while minifying removes all whitespace to reduce file size — typically by 20-40% for average payloads.

About This Tool

The JSON Formatter & Validator is a free online tool that helps you format, validate, minify, and compare JSON data. Whether you are debugging an API response, cleaning up a configuration file, or verifying that two JSON documents match, this tool handles it instantly in your browser.

Paste any JSON string into the input area and the tool will attempt to parse it. If valid, you can pretty-print it with your choice of 2 spaces, 4 spaces, or tabs indentation. Click “Minify” to strip all whitespace for production use. If the JSON is invalid, you will see the exact error message along with the line number and character position where parsing failed.

The tool also provides useful statistics about your JSON: total key count, maximum nesting depth, and size in bytes for both formatted and minified versions. This helps you understand the complexity and size impact of your data structures.

In Compare mode, you can paste two JSON documents side by side. The tool parses both and reports whether they are structurally identical. If they differ, it lists which keys were added, removed, or changed. All processing happens entirely in your browser — no data is sent to any server.

Frequently Asked Questions

What is JSON and where is it used?
JSON (JavaScript Object Notation) is a lightweight data-interchange format that is easy for humans to read and write, and easy for machines to parse and generate. It is the most common format for APIs, configuration files, and data storage in web applications. JSON supports strings, numbers, booleans, null, arrays, and nested objects.
What is the difference between pretty-printed and minified JSON?
Pretty-printed (formatted) JSON uses indentation and line breaks to make the structure visually clear, making it easier to read and debug. Minified JSON removes all unnecessary whitespace to reduce file size, which is ideal for network transmission and production APIs. A 100KB pretty-printed JSON file might shrink to 60KB when minified.
What are common JSON formatting errors?
The most common errors are: trailing commas after the last item in an array or object (not allowed in JSON), single quotes instead of double quotes for strings, unquoted keys, missing commas between items, and using JavaScript-specific values like undefined or NaN. This tool highlights the exact line and character position of any error.
How does the JSON compare feature work?
The compare mode lets you paste two JSON documents side by side. It parses both, then reports whether they are structurally identical. If they differ, it lists which keys were added, removed, or changed in value. This is useful for comparing API responses, configuration diffs, or verifying data transformations.
Is my JSON data stored or sent to a server?
No. All formatting, validation, minification, and comparison operations happen entirely in your browser using JavaScript. Your JSON data never leaves your device -- nothing is sent to any server, stored, or logged. The tool works completely offline once the page loads.

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