Formatted JSON will appear here
What is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format defined in RFC 8259. It uses human-readable key-value pairs and ordered lists, making it the dominant format for REST APIs, configuration files, and NoSQL databases.
JSON Data Types
- String
"Hello, world" - Number
42, 3.14, -7 - Boolean
true, false - Null
null - Object
{ "key": value } - Array
[ 1, 2, 3 ]
Common JSON Use Cases
- → REST API request & response bodies
- → Configuration files (package.json, tsconfig.json)
- → NoSQL database documents (MongoDB, Firestore)
- → Server-to-browser data transfer
- → Webhooks and event payloads
- → CI/CD pipeline definitions
How to Use This JSON Checker
Paste or Upload
Paste your JSON directly into the editor, or click Upload to select a .json file from your device. All processing is local.
Instant Validation
The tool validates your JSON in real time. If there is an error, it shows the exact message and line number so you can fix it immediately.
Format or Minify
Click Beautify to pretty-print your JSON with indentation, or Minify to compact it. Then copy to clipboard or download the result.
Common JSON Errors & How to Fix Them
✗ Trailing comma
Invalid
{ "a": 1, }Valid
{ "a": 1 }JSON does not allow a comma after the last item in an object or array.
✗ Single-quoted strings
Invalid
{ 'name': 'Alice' }Valid
{ "name": "Alice" }All strings and keys in JSON must use double quotes.
✗ Unquoted key
Invalid
{ name: "Alice" }Valid
{ "name": "Alice" }Every key in a JSON object must be wrapped in double quotes.
✗ Comments in JSON
Invalid
{ // name
"name": "Alice" }Valid
{ "name": "Alice" }JSON does not support // or /* */ comments. Use JSONC format if you need comments.
Frequently Asked Questions
Yes — completely. All processing happens inside your browser using JavaScript. Your JSON is never sent to any server, stored, or logged. You can even turn off Wi-Fi and the tool still works.
The most common JSON errors are: missing commas between items, trailing commas after the last item, unquoted or single-quoted keys, and invalid escape sequences. Paste your JSON here and the checker will show the exact character position so you can fix it quickly.
Formatting (pretty-printing) adds indentation and line breaks to make JSON readable by humans. Minification removes all unnecessary whitespace to shrink file size for faster API transfers. Use formatting for debugging; use minification for production.
Yes. Click the Upload button to select any .json file from your device. The file is read locally — it never leaves your browser, making it safe for files containing private or sensitive data.
This checker detects all standard syntax errors: missing/extra commas, unclosed braces or brackets, unquoted keys, single-quoted strings, invalid Unicode escapes, comments (not valid in JSON), trailing commas, and values like NaN or Infinity.
Depth is the maximum nesting level in your JSON. A flat object {"name":"John"} has depth 1. If it contains a nested object, depth becomes 2, and so on. Very high depths (>10) can indicate overly complex data structures.
Once the page has loaded, yes. All validation, formatting, and analysis run client-side in JavaScript with no network requests required.
JSON (JavaScript Object Notation) is the standard format for REST API requests and responses, configuration files (package.json, tsconfig.json), data storage in NoSQL databases like MongoDB, and inter-service communication in microservices.