A JSON validator is a free online tool that strictly checks whether your text is valid JSON and explains failures in plain English. Instead of a cryptic parser message, you get the exact line and column plus practical hints for the most common mistakes, like trailing commas or single quotes.
How do I check if my JSON is valid?
Paste it into the validator and press Validate. A green message confirms valid JSON along with its type and size. A red message explains the error with the exact line and column, and the hints box suggests the likely fix for common mistakes.
This validator uses the same strict JSON.parse rules as every browser and server: double-quoted strings and keys, no trailing commas, no comments, no unquoted keys. If it passes here, it will parse anywhere.
What are the most common JSON mistakes?
Trailing commas after the last item, single quotes around strings, unquoted object keys, JavaScript-style comments, and mismatched brackets account for almost every failure. The tool scans for each of these and tells you which one it found.
A frequent gotcha is copying a JavaScript object literal and pasting it as JSON: object literals allow trailing commas and unquoted keys, but JSON does not. Another is smart quotes from word processors, which must be replaced with straight double quotes.
Frequently asked questions
Is this JSON validator free?
Yes. Validate unlimited JSON documents with no account and no limits. It runs entirely in your browser.
What does "Unexpected token" mean?
It means the parser found a character it did not expect at that position. Check the reported line and column: the usual causes are trailing commas, single quotes, or a missing quote or bracket just before that spot.
Can it validate a JSON array too?
Yes. Any valid JSON value validates: objects, arrays, strings, numbers, booleans, and null.
Why is a trailing comma invalid in JSON?
The JSON specification simply does not allow them, unlike JavaScript. Remove the comma after the last item in every object and array.
Is my JSON uploaded anywhere?
No. Validation happens locally in your browser. Your data is never sent to a server.