How it works
What Stillmark does
Stillmark records a fingerprint of your files in a public, permanent ledger, so you can later show that those exact files existed, unchanged, no later than a specific time.
What we see
Your device computes a SHA-256 fingerprint of each file. Only the fingerprints and file names are sent to us. The files themselves never leave your device.
How long it takes
Paid commits are recorded in a batch every few minutes, usually within 10 minutes of payment. Free demos take a few minutes. Your receipt page updates on its own, and we email you when your proof is ready.
What you get
A proof file (.stillmark.json) and a PDF Stillmark receipt. Together with your original files, they are all anyone needs to check your proof — now or in many years, with or without us.
What if I lose the proof?
Open Verify and drop the original file. If it was committed, we find its proof and you can download it again.
What if I change the file?
Any change, even one byte, gives a different fingerprint, and the proof will no longer match. Keep the original exactly as it was. Re-saving a document or editing a photo's details counts as a change.
How anyone can check a proof
Drop the proof file (and, if you like, the original file) on Verify. The check runs in your browser: it recomputes the fingerprints, follows the proof to the recorded root, and reads the Base transaction directly from the public network. There is also an open-source verifier anyone can run without this site.
What a proof shows — and what it does not
It shows that these exact bytes existed no later than the recorded time, and that they are unchanged since. It does not show who created or owns a file, that its contents are true or original, or anyone's identity or signature.
Under the hood
Your files' fingerprints, together with a random value unique to your commit, form a Merkle tree. Its root is combined with other commits into a batch, and the batch root is written into a transaction on Base, a public network. Each proof carries the path from your file to that transaction, so it can be checked step by step.
Refunds
See Refunds. Questions: [email protected].