Question 1

Is my data sent to a server?

Accepted Answer

No. Parsing uses the browser's own JSON.parse and no request leaves the page, so it's safe to paste production data.

Question 2

Why do I get an "Unexpected token" error?

Accepted Answer

The three usual causes: single quotes instead of double quotes around keys, a trailing comma after the last element, and comments. All three are valid JavaScript but not valid JSON.

JSON Formatter