Verify a document

Drop in a file and find out whether we hold those exact bytes, when we first captured them, and whether that capture is anchored to the Bitcoin blockchain.

The file never leaves your computer. Its fingerprint is computed in your browser and only that 64-character string is sent to us.

What a match does and does not prove

A confirmed anchor proves that the exact bytes you supplied existed no later than the Bitcoin block they were recorded in. Nobody, including us, can backdate a hash into a block that is already mined. So if a body later edits or removes a document, our copy can be shown to predate the change.

It does not prove the document is authentic, or that any government body ever published it. It proves we held those bytes by that time. Where the document came from is recorded separately, in the capture: the URL we fetched, the HTTP status the server returned, and the moment we fetched it.

You do not have to take our word for any of this. Every proof is a standard OpenTimestamps file, checkable with the upstream ots tool against the public Bitcoin blockchain — with or without this website existing.