Hi Product Hunt! 👋

I'm Cristian, an independent developer based in Barcelona, and the person behind Sellat.

I started building Sellat around a simple question: if someone challenges a document, a transaction or a digital record months later, how can you prove exactly what existed at that moment?

A screenshot or a database entry isn't always enough. I wanted evidence that anyone could verify independently, without having to trust me or my service.

That idea grew into Sellat: one proof infrastructure with three ways to use it.

People: protect files directly from the web.
Businesses: integrate verifiable evidence into their systems through an API.
AI agents: create proofs and pay per request using x402, without an account.

Behind all three is the same infrastructure: SHA-256 fingerprints, Polygon and Bitcoin anchoring, optional qualified eIDAS timestamps, and portable evidence packages.

One important distinction: Sellat doesn't prove that a document is true. It helps prove that a specific version existed at a certain time and hasn't changed.

My broader vision is to make verifiable evidence accessible in a world where AI is making it increasingly difficult to know what to trust.

I'm building this independently, and I'd genuinely love your feedback.

Where do you think verifiable digital evidence could be most useful — documents, business transactions, AI agent activity, or something else?

Thanks for taking a look!

Cristian