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Validate JSON instantly and find syntax errors with clear, developer-friendly messages — processed entirely in your browser.
Formatted JSON will appear here after you click Format.
JSON validation checks whether a piece of text follows the JSON syntax rules defined by the JSON standard. Valid JSON can be parsed by any compliant parser; invalid JSON throws an error. Validating before you ship data catches typos that would otherwise break an API request, a config load, or a data import.
This validator parses your input with the browser’s strict JSON parser and reports the first error it finds, including the line and column, so you can fix it quickly.
Most “invalid JSON” messages come from breaking one of these rules:
"name", not name or 'name'.{ } and arrays in [ ].true, false, or null.// or /* */) are not part of standard JSON.NaN and Infinity are not valid JSON.{
"name": "John",
"age": 30
}{
"name": "John",
"age": 30,
}The second example is invalid because of the trailing comma after 30. JSON does not allow a comma after the final property of an object (or the final element of an array), even though many programming languages do. Removing that comma makes it valid.
JSON validation checks whether text follows the JSON syntax rules defined by the JSON standard. Valid JSON can be parsed by any compliant parser; invalid JSON will cause errors.
Common causes include trailing commas, single quotes instead of double quotes, unquoted property names, missing commas or brackets, and comments — none of which are allowed in standard JSON. The validator reports the line and column of the first error.
No. A comma after the last element of an array or the last property of an object is invalid in standard JSON, even though many programming languages permit it.
No. The JSON standard does not include comments. If you need comments, remove them before validating, or use a superset such as JSON5 (which this tool does not target).
No. Validation runs entirely in your browser. Your data never leaves your device.