Back to JSON Tools

JSON Lint Online

Lint and validate JSON syntax with our free JSON Formatter & Validator. Get detailed error messages with line numbers for quick fixes.

Why Lint Your JSON?

Invalid JSON is one of the most common causes of silent failures in web applications. A missing comma, unquoted key, or mismatched bracket can break an entire API response, configuration file, or data pipeline. A JSON linter catches these errors before they reach production, saving hours of debugging time.

Common JSON Errors Detected

Trailing comma

{ "name": "John", }

Remove the comma after the last element in an object or array

Unquoted keys

{ name: "John" }

Wrap all object keys in double quotes

Single quotes

{ 'name': 'John' }

Use double quotes for strings — single quotes are not valid JSON

Mismatched brackets

{ "name": "John" ]

Ensure braces {} and brackets [] are properly paired and nested

Invalid number formats

{ "value": 0123 }

Remove leading zeros from numbers (use string for zip codes)

Lint JSON Now →