JSON Validator

What it does

Checks whether text is valid strict JSON and, when it is not, points at the exact problem.

Errors you can act on

Instead of a bare character offset or a generic engine message, you get the line and column and a plain-language cause: a trailing comma, a missing colon, an unterminated string. The caret lands on the exact character. Duplicate keys are reported as warnings rather than hidden, because a strict parser keeps only the last one.

Strict, not JSONC

This validates the JSON standard: comments and trailing commas are rejected. If your file is meant to have them, it is JSONC, and a validator that accepted them would be telling you invalid JSON is valid. To turn JSON-ish text into strict JSON, use Repair instead.

Privacy

Validation happens in your browser. Nothing is uploaded; it works offline.