What counts as valid JSON?

Valid JSON must follow the RFC 8259 specification: objects use curly braces with double-quoted keys, arrays use square brackets, and values can be strings, numbers, booleans, null, objects, or arrays. Trailing commas and single quotes are not allowed.

Can it validate JSON with comments?

Standard JSON does not support comments. If your JSON contains comments (like JSONC), they will be flagged as syntax errors. You would need to strip comments before validation.

Does it validate against a JSON Schema?

This tool validates JSON syntax, not JSON Schema. It checks whether the JSON is well-formed, not whether it conforms to a specific schema definition.

How to Check JSON Validity Online

Validate any JSON string and pinpoint syntax errors instantly with our free JSON validator. No installation required.

Steps

Open the JSON Formatter

Navigate to the JSON Formatter tool. Validation is built into the formatting process.

Paste your JSON

Paste the JSON you want to validate into the input area.

Check the result

If the JSON is valid, it will be formatted and displayed with syntax highlighting. If it is invalid, a detailed error message shows the line number and character position of the problem.

Common JSON Errors

The most frequent JSON errors are trailing commas after the last item in an object or array, missing or mismatched quotes, unescaped special characters in strings, and using single quotes instead of double quotes. A good validator catches all of these instantly.