Where exactly is this JSON broken?
Paste a URL or a blob of JSON. Parseproof tells you the exact line, column, and what went wrong — in plain language. Then it shows you the full server response so you can tell whether the JSON was malformed, or the server never sent JSON at all.
Two modes, one purpose
Drop in a JSON blob
Paste any JSON text. Parsing happens entirely in your browser —
your content never leaves your machine. If the JSON is valid, you see
it pretty-printed. If it is not, Parseproof pinpoints the error with a
caret (^) marker and explains what was expected in plain
language instead of “unexpected token at position 4471.”
Inspect a live API response
Enter a URL. Parseproof proxies the request server-side and returns the HTTP status, response headers, and full body. It flags content-type mismatches, HTML error pages masquerading as 200 responses, and Cloudflare-hosted endpoints that cannot be reached.
What makes it different
Line and column precision
Instead of an opaque byte offset, Parseproof shows you the error location with a caret diagram and surrounding context lines.
Raw server evidence
Sees the actual Content-Type, the body bytes, and the status code — so you can tell when the server sent HTML labelled as JSON, or an error page on a 200 status.
Cloudflare-aware
A Worker cannot reach another Cloudflare-hosted site. Parseproof detects this and tells you, rather than reporting a false “connection refused.”
Your data stays yours
Pasted JSON is parsed in your browser — nothing is transmitted. URL fetches are proxied but not stored or logged on our side.
Try it now
No signup, no account, no data collection. Open the tool and paste your JSON.
Open Parseproof