Proof of existence: how to show your file existed on a certain date

You send a logo concept to a client who does not hire you, and a month later something very similar appears on their website. A photo you took shows up in someone else's portfolio. A partner claims your proposal arrived after the deadline. In each case the question is the same: can you show that this exact file existed on a given date?

How proof of existence works

Every file has a fingerprint, a SHA-256 hash: a 64-character code calculated from its contents. The same file always gives the same fingerprint, and changing even one pixel or comma gives a completely different one. You cannot work backwards from the fingerprint to the file.

Proof of Existence records that fingerprint together with the time, the file name and size, and gives you a PDF certificate with a QR code. Later, anyone can drop the original file on the verification page to confirm it matches the record.

1. Upload any file up to 10 MB: an image, a design file, a PDF, a ZIP of your source code, an audio clip.
2. Click Process and download the certificate.
3. Keep the original file exactly as it is, together with the certificate.

Your file stays private

The file is processed in memory only to compute its fingerprint, then discarded. Only the fingerprint, name, size and time are stored, so you can register unreleased designs or confidential drafts without publishing them.

What it proves, and what it does not

• It proves that this exact file existed no later than the registration time.
• It does not prove who created the file. Someone else could register a copy of your work too; the earliest registration is what counts, so register early.
• It is not a qualified electronic timestamp under laws such as eIDAS, and it does not replace copyright registration where that exists. Treat it as supporting evidence alongside your drafts, emails and source files.

Register each important version. An edited file has a new fingerprint, so version 2 needs its own record.