You don't have to take our word for it.
Drop in a file and we recompute its SHA-256 fingerprint and check it against our sealing register. You get one of three answers, and they mean different things: a KuduDoc account sealed it, somebody stamped it with our free public tool, or we have no record of it at all. Free, no account, no sign-in.
Residential-Lease-Agreement.pdf
An illustration of the summary page added to a completed document — not a real result.
Check a document in seconds
Drop in a PDF you've received from KuduDoc, or paste the fingerprint printed on its certificate page. We'll recompute it fresh and compare — right here, right now.
Drag a PDF here, or click to browse
Any PDF you've received from KuduDoc
64 hex characters — spaces don't matter. It's printed on the last page of every completed KuduDoc document.
This does not check a document
A lookup tells you whether a document with that fingerprint was ever sealed — nothing more. It cannot tell you anything about a file you are holding, because the fingerprint is printed on the document: anyone who altered a document could print a fingerprint copied from a genuine one. If you want to know whether your document is intact, upload it. We recalculate the fingerprint from its actual bytes and compare.
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Checked just nowFile
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SHA-256 fingerprint
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OpenTimestamps / Bitcoin anchor
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What an uploaded-file result means — precisely
- This exact file existed on the date shown, and hasn't changed by a single byte since.
- Anyone holding a copy can run this same check and get the same answer.
- It does not mean KuduDoc has checked whether the document is true, accurate or lawful.
- It does not authenticate handwriting, or verify a scan against the paper it came from.
- It does not confirm who signed, unless a named party has confirmed it above or an identity check was attached.
A seal is a fact about a file, not an endorsement of what the file says. We keep that line bright on purpose.
This reads the file you drop in. It is sent to KuduDoc, fingerprinted with SHA-256, and checked against our sealing records — the answer you get back is about your file, not a sample. We do not keep the file; the check itself is logged, with the fingerprint and the time. If you would rather not send the document itself, paste its fingerprint instead: that tells you whether such a document was ever sealed, but it cannot tell you anything about the file in your hands. Either way it is free and needs no account.
Three checks, all outside KuduDoc's control
Grab the file or the fingerprint
Use the PDF you were sent, or copy the 64-character fingerprint printed on its certificate page.
We recompute, not just look up
KuduDoc hashes the file fresh and compares it with what was recorded the moment it was completed — one changed byte and the numbers won't match.
See who sealed it, and who did not
The result says whether an identified KuduDoc account sealed the document or somebody used our free public stamping tool — where we cannot tell you who. If a named party has been asked to confirm the document, their answer is shown too, including a refusal.
Two honest details. KuduDoc's certification signature is currently self-signed, not issued by a paid certificate authority: open a certified PDF in Adobe Reader and it reports the signature's validity as "unknown" rather than showing a green tick. That is expected. And an OpenTimestamps anchor is submitted when a document is sealed but only confirmed in Bitcoin some hours later, so a result will often say the anchor is submitted rather than confirmed. We show the anchor's real state instead of a tick.
Your next document deserves the same proof.
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