Maptheory
JSON Validator

Validate JSON Syntax Online

Check if your JSON is valid instantly. Get detailed error messages with line numbers to quickly find and fix syntax problems.

Real-time Validation

Syntax is checked as you type with instant feedback

Detailed Errors

Error messages with exact line and column numbers

Auto Format

Valid JSON is automatically beautified with indentation

Enter JSON to validate
1 line

Common JSON Syntax Errors

Single quotes

{'name': 'John'}
{"name": "John"}

JSON requires double quotes for strings and keys

Trailing comma

{"a": 1, "b": 2,}
{"a": 1, "b": 2}

Remove comma after the last item

Unquoted keys

{name: "John"}
{"name": "John"}

Keys must be wrapped in double quotes

Missing comma

{"a": 1 "b": 2}
{"a": 1, "b": 2}

Add comma between items

Frequently Asked Questions

What is JSON validation?▼
JSON validation checks if a string follows the JSON (JavaScript Object Notation) syntax rules. Valid JSON must use double quotes for strings, proper bracket matching, correct comma placement, and valid data types (strings, numbers, booleans, null, arrays, objects).
What are common JSON syntax errors?▼
Common errors include: single quotes instead of double quotes, trailing commas after the last item, missing commas between items, unquoted keys, unescaped special characters in strings, and mismatched brackets or braces.
How do I fix 'Unexpected token' errors?▼
This usually means there's a syntax error near the indicated position. Check for: missing quotes around strings, missing commas between items, extra commas at the end of arrays/objects, or invalid characters.
Can I validate JSON with comments?▼
Standard JSON doesn't support comments. If your JSON has comments (// or /* */), it's technically invalid. Some parsers accept JSONC (JSON with Comments), but for compatibility, you should remove comments.
Is my data secure when validating?▼
Yes, completely. All validation happens in your browser using JavaScript. Your JSON data is never sent to any server.
What's the difference between validation and formatting?▼
Validation checks if JSON is syntactically correct. Formatting adds proper indentation and line breaks to make valid JSON more readable. Our tool does both.

Need More Features?

Convert JSON to YAML, XML, CSV, or TypeScript interfaces. Compare JSON with diff view.

Full JSON Formatter

Related Tools

Explore more utility tools that might help with your workflow.

QR Code Generator

Create QR codes for URLs, WiFi, contacts, emails, and more. Customize colors and add logos.

Base64 Encoder/Decoder

Encode and decode Base64 strings and files with URL-safe options and file support.

File Converter

Convert documents, images, and data files. Word to PDF, PNG to JPG, JSON to CSV, and 25+ more conversions.

View all tools