Check the file in your hands.
Choose the PDF you were sent, or open the seal link on its certificate. Your browser works out its SHA-256 fingerprint on your device and sends only that fingerprint to our sealing register. The PDF stays on your device. Free, no account, no sign-in.
Drop a PDF here, or choose one
The completed document you were sent. It stays on this device.
A lookup says whether a document with this fingerprint was sealed. It says nothing about the file in your hands: choose the file under Check a PDF to check that.
Your browser works out the fingerprint on this device and sends only that fingerprint. The file itself is never sent. We log the fingerprint, the time, your network address and your browser.
Three possible answers. Sealed by a KuduDoc account, stamped with the free tool, or no matching record. The file you check never leaves your device. What a seal can tell you →
How the check works
Three steps. One plain answer.
- 1
Bring the file or its seal link.
Choose the PDF you were sent, open the seal link on its certificate, or paste the fingerprint printed there. A printed code can be copied onto any document, so checking the file itself is the check that counts.
- 2
Your browser recomputes, not just looks up.
Your browser fingerprints the file afresh on your device and sends only that fingerprint, which we compare with the one recorded when it was sealed. One changed byte and they no longer match.
- 3
See what the record says.
The answer says whether a KuduDoc account sealed it, someone used the free stamping tool, or there is no record. If a named party was asked to confirm the document, their answer is shown too.
When you check a sealed document
The record matters as much as the match.
The seal link on a completed document's certificate opens this page with its seal record. Confirm the intended file and version, then read file integrity, certificate trust and time evidence separately.
A submitted or pending OpenTimestamps anchor is not confirmed Bitcoin anchoring. Even a matching file does not establish a person’s identity or the truth of the document’s contents.