Check JSON Syntax Online
Instantly Validate JSON and Locate Syntax Errors
Need to use Check JSON Syntax Online right now?
A single missing comma or unclosed bracket can silently break a config file or API request, and manually scanning JSON for the exact error is slow. Paste your JSON in and this tool validates it instantly, pointing to exactly where the syntax breaks if it's invalid.
JSON to validate
Paste JSON above to check whether it's valid.
Features
- Runs entirely in your browser
- Privacy-first — your data is never uploaded
- Real-time, instant results
- 100% free, no sign-up required
- Works on desktop, tablet, and mobile
- No installation needed
Who uses this tool?
About Check JSON Syntax Online
JSON has strict, unforgiving syntax rules: every key must be wrapped in double quotes (not single quotes), no trailing commas are allowed after the last item in an object or array, and every opening brace or bracket needs its matching close. A JSON validator checks a piece of text against those rules and tells you definitively whether it's valid JSON — and if it isn't, exactly what's wrong and roughly where the problem is, rather than leaving you to scan line by line looking for a stray comma.
This matters constantly in real development work: an API is returning a 500 error and you suspect the request body you're sending isn't valid JSON, a config file mysteriously isn't loading and you want to rule out a syntax error before debugging deeper, or you're hand-editing a JSON file and want a quick sanity check before saving. A validator answers the single most basic but most important question — "is this even parseable?" — before you invest time debugging something further downstream.
This tool uses the browser's native JSON parser to check validity, which means it enforces exactly the same rules any JavaScript environment, most APIs, and virtually every JSON-consuming system in the world will enforce — there's no risk of a validator being looser or stricter than the systems that will actually consume your JSON. On success, it also reports the top-level data type (object, array, string, number, or boolean) and, for objects, how many top-level keys it has — useful confirmation that you're looking at the structure you expect.
On failure, the exact parser error message is shown, which typically identifies the type of problem (unexpected token, unexpected end of input, etc.) and its approximate position in the text — enough information in the overwhelming majority of cases to go straight to the specific character or line causing the issue, rather than needing to guess.
How it works
- Paste your JSON. Enter the JSON text you want to check.
- See the instant result. A clear valid/invalid status appears immediately, with details on either side.
- Fix and re-check. Adjust your JSON based on the error message and watch the status update live.
Examples
Invalid JSON (trailing comma)
Input
{"name": "ToolsForge", "free": true,}Output
Invalid JSON — Unexpected token } in JSON at position 36