JSON Validator
Instantly check whether JSON is syntactically valid — shows the exact line and column of any error.
What is a JSON Validator?
A JSON validator checks whether a JSON string follows the JSON specification (RFC 8259). It verifies correct syntax — properly quoted strings, no trailing commas, no comments, and a single root value — and reports the exact line and column of any error.
The most common JSON syntax errors are trailing commas, single-quoted strings, unquoted keys, and mismatched brackets. For example, this is invalid JSON:
{
'name': 'Alice', // single quotes and comment — both invalid
"age": 30, // trailing comma
}
The validator uses the browser's native JSON.parse() function, which follows RFC 8259 strictly. All processing runs entirely in your browser — no data is sent to any server.
Frequently Asked Questions
- What is a JSON validator?
- A JSON validator checks whether a JSON string follows the JSON specification (RFC 8259) — correct syntax, properly quoted strings, no trailing commas, no comments, and a single root value. It reports the exact line and column of any syntax error.
- What are the most common JSON validation errors?
- Trailing commas after the last item in an array or object, single-quoted strings instead of double-quoted, unquoted keys, comments (JSON has no comment syntax), and missing or extra braces or brackets.
- Is my JSON data sent to a server?
- No. All validation runs entirely in your browser using the native JSON.parse() function. Your data never leaves your machine.
- What is the difference between JSON validation and JSON Schema validation?
- Syntax validation checks that the JSON is well-formed — correct braces, quotes, and value types. JSON Schema validation additionally checks that the data matches a schema — required fields, value types, minimum/maximum values, and string patterns. This tool performs syntax validation. For schema validation, use tools like Ajv (JavaScript) or jsonschema (Python).
- Why does valid JSON sometimes fail in my application?
- The JSON may be syntactically valid but semantically wrong — missing required fields, wrong value types, or values outside allowed ranges. Check the application's schema or API documentation for data requirements beyond basic JSON syntax.
Related Tools
Other free developer tools available on DevFormatter.
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Format, validate, minify, and sort JSON. Detects duplicate keys and converts to YAML.
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XML Validator
Check XML for well-formedness and validate structure with exact error positions.