Is my JSON data uploaded to a server?

No. Everything runs entirely in your browser with JavaScript. Nothing is sent over the network, which makes the tool safe for sensitive data.

What do I get when the JSON is valid?

A short report: the root type (object, array…), the number of keys or items, and the document size. Enough to sanity-check what you pasted.

How precise are error messages?

The validator surfaces the JavaScript engine’s parse error and adds the line and column, so you can jump straight to the offending character.

100% local — your data never leaves your browser

JSON Validator — Check JSON Syntax Online for Free

Validate JSON syntax instantly in your browser, with line and column on errors. Free, private and offline-friendly: your data never leaves your device.

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JSON input

Result output

Why validate JSON?

A single trailing comma or unquoted key breaks an entire JSON document — often deep inside a config or an API response. Paste your JSON above to check it instantly.

How it works

The validator runs JSON.parse locally in your browser. On success it reports the root type and size; on failure it shows the parser’s message enriched with the exact line and column. The input editor also underlines syntax errors as you type.

Frequently asked questions

Is my JSON data uploaded to a server?: No. Everything runs entirely in your browser with JavaScript. Nothing is sent over the network, which makes the tool safe for sensitive data.
What do I get when the JSON is valid?: A short report: the root type (object, array…), the number of keys or items, and the document size. Enough to sanity-check what you pasted.
How precise are error messages?: The validator surfaces the JavaScript engine’s parse error and adds the line and column, so you can jump straight to the offending character.