JSON Checker - Free Online JSON Viewer, Formatter & Validator

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About JSON Checker

JSON Checker is a free, powerful online tool for developers to check, view, format, validate, and edit JSON data. Whether you're debugging an API response, cleaning up configuration files, or exploring complex data structures, our tool makes working with JSON simple and efficient.

100% Private & Secure: All JSON processing happens entirely in your browser. Your data never leaves your device and is never sent to any server. This tool works completely offline after the initial page load.

Key Features

Format & Beautify

Transform minified JSON into readable, properly indented code with a single click. Perfect for debugging and code review.

Validate & Debug

Instantly check if your JSON is valid. Get detailed error messages with exact line and column numbers to fix issues quickly.

Interactive Tree View

Explore complex JSON structures with our collapsible tree view. Click any node to see its JSONPath and copy it to clipboard.

Form-Based Editor

Edit JSON visually with our form editor. Add, remove, and modify keys and values without writing raw JSON syntax.

How to Use

Paste JSON: Simply paste your JSON data into the input area on the left.

Format: Click "Format" to beautify your JSON with proper indentation.

Validate: Click "Validate" to check if your JSON is syntactically correct.

Explore: Click "Tree" to view your JSON as an interactive tree structure.

Edit: Click "Form" to edit your JSON using a visual form interface.

Export: Use the download button to save your formatted JSON as a file.

Common JSON Errors

Missing quotes: All keys and string values must be wrapped in double quotes ("key", not 'key').

Trailing commas: JSON doesn't allow commas after the last item in objects or arrays.

Unescaped characters: Special characters like backslash, quotes, and newlines must be escaped.

Single quotes: JSON requires double quotes ("), not single quotes (').

Comments: Standard JSON doesn't support comments (// or /* */).

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Frequently Asked Questions

What is JSON?

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's based on a subset of JavaScript and is commonly used for transmitting data between a server and web application, configuration files, and data storage.

Is my JSON data safe when using this tool?

Yes, absolutely. All JSON processing happens entirely in your browser using JavaScript. Your data never leaves your device and is never sent to any server. This tool works 100% offline after the initial page load, making it safe for sensitive data.

How do I format JSON?

Simply paste your JSON into the input area and click the "Format" button. The tool will automatically add proper indentation and line breaks to make your JSON readable. You can also use the "Minify" button to remove all whitespace for compact storage or transmission.

What causes JSON validation errors?

Common JSON validation errors include: missing or extra commas, unquoted keys, single quotes instead of double quotes, trailing commas after the last item, unescaped special characters in strings, and using comments (which aren't allowed in standard JSON). Our validator shows the exact line and column where the error occurs.

Can I edit JSON directly in the tree view?

The tree view is read-only and designed for exploring JSON structure. For editing, use the Form view which provides an intuitive interface to modify keys and values, add new properties, or delete existing ones. Changes are automatically synced back to the input editor.