Prove that a file existed — and has not changed

Your photo, contract, recording or drawing gets a timestamp anyone can check, including someone who does not trust you and does not trust us. It is free, needs no account, and the file never leaves your computer.

What it proves

  • This exact file existed no later than the stamped moment.
  • Not a single byte has changed since.
  • The other side can check both without asking us for anything.

What it does not prove

  • That you are the author, or that you own the rights.
  • That anything inside the document is true.
  • That the file did not exist earlier — only that it existed by then.

How it works, in four steps

  1. Your browser reads the file and computes its fingerprint — a SHA-256 hash, 64 characters. The file itself stays on your device.
  2. Only that fingerprint is sent and written into a public log that can be added to, but never rewritten.
  3. At the end of the week every fingerprint of that week is combined into one value, which is signed and then published into Bitcoin and recorded against a bank reference.
  4. From then on your proof no longer depends on us being here, or being honest.

Stamp a file now

The mistake that quietly voids your proof

Never send the stamped file through a messenger and keep only that copy.

Most messengers and social apps recompress photos and strip their metadata. What comes out the other end looks identical to a human and is a different file to a computer: a different fingerprint, and your proof no longer matches it. The same happens when an editor re-saves an image, when a scanner is set to “optimise”, or when a document is exported to PDF a second time.

So keep the original, byte for byte, exactly as it was stamped — that file is the evidence. Send copies wherever you like; they simply are not the thing you proved.

What you hand over in a dispute

Three things, and the other side needs nothing from us to check them:

An expert can follow that chain end to end without a single call to this website. That is the point: evidence that depends on our goodwill is not evidence.

Different courts and experts trust different things — a bank record, the Bitcoin network, a public archive. BeatTime anchors the same fact in all of them, so you can present the one your court trusts, or all of them together. Each can be checked without us.

Where people use this

A photographer or designer

You stamp the original shot or the working file the day you make it. If the same image later appears elsewhere with someone else's name on it, you can show your copy existed before theirs — and that it is the very file you are holding, not a lookalike.

A journalist or researcher

You stamp a document, a recording or a page you archived. If the source later disappears or changes, you can show what you had and when you had it, without revealing the content to anyone in the meantime — only the fingerprint was ever sent.

An engineer, inventor or contractor

You stamp a drawing, a calculation or a version of a specification when it is finished. Later you can show that this exact version existed on that date — useful when a project is reconstructed years afterwards and everybody remembers it differently.

The honest legal paragraph

We are not a qualified trust service provider under the EU eIDAS Regulation, so this timestamp does not carry the legal presumption that a qualified timestamp gets under Article 41. It is evidence that a court or the other side weighs like any other evidence — not an automatic win.

In the EU, the same Article 41 also says that an electronic timestamp may not be refused as evidence merely because it is electronic or not qualified. So it cannot be turned away for that reason alone; how much it weighs is for the court.

What we can say plainly is how it is built: the fingerprint is public and cannot be altered afterwards, the weekly value is signed and anchored in two independent places, and the whole procedure is written down in the specification so an expert can check our arithmetic rather than our word. If your matter is serious, show that page to your lawyer before you need it.

Why we would rather be checked than trusted: the BeatTime manifesto.

Cost, accounts and privacy

The service is free and there is no account. We never receive your file, its name or its size — only a 64-character fingerprint, which cannot be turned back into the file. Nothing is tracked, and no cookie is set.

One thing to keep in mind: fingerprints are public and permanent. Nobody can read your document from one, but the entry itself cannot be withdrawn.

Prefer to work from your desktop? The BeatStamp client stamps files, keeps your history and verifies proofs offline.

← Stamp a file in the browser