JSON Validator

What Is JSON Validation?

JSON validation is the process of checking whether a string of text conforms to the JSON (JavaScript Object Notation) specification defined in RFC 8259. A valid JSON document must follow strict syntax rules: all strings must use double quotes, property names must be quoted, and only specific data types (strings, numbers, booleans, null, arrays, and objects) are permitted.

Why Validate JSON?

Invalid JSON is one of the most common causes of API failures, configuration errors, and data processing bugs. A single misplaced comma or missing quote can break an entire application. Validating JSON before sending it to an API, saving it to a database, or using it in configuration files prevents hard-to-debug runtime errors. The validator checks syntax, not an application schema or business rules. Error location details depend on the browser parser.

Common JSON Syntax Errors

The most frequent mistakes developers make with JSON include:

• Trailing commas: Adding a comma after the last element in an array or object (e.g., {"a": 1,})
• Single quotes: Using 'value' instead of "value" - JSON requires double quotes
• Unquoted keys: Writing {name: "John"} instead of {"name": "John"}
• Comments: JSON does not support // comments or /* block comments */
• Missing commas: Forgetting to separate array items or object properties with commas

How This Validator Works

Our validator uses the browser's native JSON.parse() function, to check standard JSON syntax. When the browser provides a character position or line number, the tool highlights the corresponding line. Some errors, such as an incomplete document, may have no location detail. After fixing the issue, try using our JSON Formatter to pretty-print the result, or our JSON Minifier to compress it for production use.