Developer Tools
JSON Formatter & Validator
Pretty print, validate, and explore JSON data. Interactive tree view, JSONPath querying, diff comparison, and export to CSV, XML, YAML. All processing happens in your browser.
📝 JSON Input —
🌳 Tree View
🌳
Enter valid JSON to see tree view
JSON Formatter & Validator — Essential Developer Tool
JSON (JavaScript Object Notation) is the universal data format of the web — used by REST APIs, configuration files, databases (MongoDB, Firebase), and data exchange between virtually every modern application. Our free JSON formatter and validator is an essential tool for every developer: format messy JSON into clean, readable code; validate syntax with precise error messages; explore complex nested structures with an interactive tree view; query data with JSONPath; compare two JSON documents with a visual diff; and export to CSV, XML, or YAML. Everything runs locally in your browser — your API responses, config files, and data stay private.
Common JSON Errors & How to Fix Them
| Error | Example (Wrong) | Fix (Correct) | Detection |
|---|---|---|---|
| Trailing Comma | {"name": "John",} | {"name": "John"} | Last item has comma |
| Single Quotes | {'name': 'John'} | {"name": "John"} | Single quotes found |
| Unquoted Key | {name: "John"} | {"name": "John"} | Key without quotes |
| Missing Comma | {"a": 1 "b": 2} | {"a": 1, "b": 2} | No comma between items |
| Comment in JSON | {// comment "a": 1} | {"a": 1} | // or /* detected |
| Undefined Value | {"a": undefined} | {"a": null} | undefined not valid |
JSONPath Query Examples
| Query | Description | Example Result |
|---|---|---|
| $.store.name | Get a specific property | "Tech Books & More" |
| $.store.books[*].title | Get all book titles | ["JavaScript: The Good Parts", ...] |
| $..author | Find all authors anywhere | ["Douglas Crockford", ...] |
| $.store.books[0] | Get first book | {title: "JavaScript: The Good Parts", ...} |
| $.store.books[-1:] | Get last book | {title: "Design Patterns", ...} |
| $.store.books[?(@.price < 35)] | Filter by condition | Books under $35 |
| $.store.* | All children of store | [books array, employees, ...] |
| $.store.books.length | Count array elements | 3 |
Frequently Asked Questions
A JSON formatter and validator is a free online tool that helps developers work with JSON (JavaScript Object Notation) data. It performs three main functions: (1) Validation — checks if your JSON syntax is correct and highlights errors with line numbers and descriptions, (2) Formatting — transforms minified/compressed JSON into readable, indented format (pretty print) or compresses formatted JSON to save space (minify), (3) Analysis — provides a tree view for exploring nested JSON structures, counts objects/arrays/keys, and estimates data size. Our tool processes everything in your browser — your JSON data never leaves your device.
Our validator identifies common JSON errors with precise line/column numbers: (1) Missing commas between array elements or object properties, (2) Trailing commas after the last element (not allowed in JSON), (3) Unquoted property keys — all keys must be in double quotes, (4) Single quotes instead of double quotes — JSON only accepts double quotes, (5) Comments in JSON — JSON doesn't support comments (use "$comment" key as workaround), (6) Missing closing brackets or braces, (7) Invalid escape sequences in strings. Each error shows the exact location and a description of the problem.
The interactive tree view displays your JSON data as a collapsible hierarchical structure, similar to a file explorer. Each object and array can be expanded/collapsed to explore nested data. Key features: Click arrows to expand/collapse nodes, See data types with color coding (strings in green, numbers in blue, booleans in purple, null in gray, objects/arrays with distinct icons), Search within the tree to find specific keys or values, Click on any node to copy its JSONPath, and View the size of each node. This is invaluable for understanding large API responses or complex configuration files.
JSONPath is a query language for JSON, similar to XPath for XML. Our tool includes a JSONPath evaluator where you can write queries to extract specific data. Examples: "$.store.book[0].title" (get first book title), "$..author" (get all authors anywhere in the JSON), "$.store.book[?(@.price < 10)]" (filter books under $10), "$.store.book[-1:]" (get the last book), "$.store.*" (get all children of store). Results are highlighted in both the tree view and a separate results panel. Perfect for testing API responses and data extraction.
Yes! Our JSON diff tool compares two JSON documents side-by-side and highlights the differences. It shows: Added keys (present in second JSON but not first), Removed keys (present in first JSON but not second), Changed values (different values for the same key), Unchanged sections (grayed out for context). The diff works on nested structures and arrays, making it perfect for comparing API responses, configuration changes, or database record versions. You can also see a summary of total additions, deletions, and modifications.
We support multiple export/conversion formats: Pretty Print JSON (formatted with 2-space indentation), Minified JSON (compressed, no whitespace — smallest file size), CSV (converts flat JSON arrays to CSV format), XML (converts JSON to XML structure), YAML (converts JSON to YAML format — cleaner for configuration files), and Copy to clipboard (formatted or minified). You can also download the formatted JSON as a .json file. Each format is generated in your browser with no data transmission.
Since processing happens in your browser, limits depend on your device's memory. Most modern devices can handle: JSON up to 10MB smoothly, Files with up to 100,000 lines, Deeply nested structures (up to 1000 levels), and Large arrays with thousands of elements. For very large files (>50MB), we recommend using the tree view sparingly and working with the formatted text view. The tool shows a performance warning if your JSON approaches your browser's limits. For production use with massive datasets, consider using jq or a desktop tool.
Yes! Our tool includes a built-in JSON editor with syntax highlighting, auto-indentation, and real-time validation. Features: Syntax highlighting for strings, numbers, booleans, null, and keys, Auto-indentation as you type, Real-time error detection with red underlines, Line numbers for easy reference, Undo/redo support, and Auto-completion suggestions for closing brackets. The editor works like a code editor specifically optimized for JSON editing. Changes are reflected in real-time in the tree view.
While JSON is derived from JavaScript, there are key differences: (1) JSON keys must be double-quoted strings; JavaScript allows unquoted keys, (2) JSON only supports double quotes; JavaScript accepts single quotes, (3) JSON doesn't support comments; JavaScript does, (4) JSON doesn't allow trailing commas; JavaScript does, (5) JSON is purely data; JavaScript objects can contain functions, (6) JSON only supports null; JavaScript has undefined. Our validator helps catch these differences when converting between JSON and JavaScript.
Our JSON to CSV converter handles flat JSON arrays automatically: Each object in the array becomes a row, Object keys become column headers, Nested objects are flattened with dot notation, and Missing keys in some objects are handled gracefully. For Excel: Export as CSV and open in Excel, or use our formatted output. For complex nested JSON: Use the tree view to explore the structure first, then use JSONPath to extract the specific data you need before converting to CSV. This gives you clean, structured data for spreadsheet analysis.
Absolutely! 100% of JSON processing happens in your browser using JavaScript. Your data is NEVER sent to any server, cloud, or third-party service. No one can see, access, or intercept your JSON. This is critical because JSON often contains: API keys and authentication tokens, User data and personal information, Business logic and proprietary configurations, Database records, and Financial data. You can verify this by disconnecting your internet after loading the page — all features continue working. For maximum security, use this tool for sensitive production data with complete confidence.
Professional JSON best practices: (1) Always validate JSON before using it in production — our validator catches syntax errors instantly, (2) Use consistent indentation (2 spaces is the standard), (3) Avoid deeply nested structures (more than 5-6 levels becomes hard to maintain), (4) Use meaningful, camelCase key names, (5) Don't include comments — use a "$comment" or "_comment" key if needed for documentation, (6) Keep JSON files under 1MB when possible for API performance, (7) Minify JSON for production to reduce bandwidth, (8) Always pretty-print JSON in version control for readable diffs.