Mathvsmyth
Your content never leaves here.
Compute the SHA-256 hash on your own device. Nothing is uploaded to any server: everything happens in your browser.
Step 1 · Compute your hash
Choose a file or paste your text. The hash appears below, on your device.
Step 2 · Timestamp it (free)
Take your hash to an OpenTimestamps stamper (e.g., opentimestamps.org): paste only the hash, not your content. Public calendars batch it with thousands of seals in one Bitcoin transaction they pay for. You will receive an .ots receipt: keep it private.
Step 3 · Reveal when you decide
When you patent or decide to publish, show the document: anyone will verify its hash matches the one you sealed on that date. Proof you had it that day, without having shown it before.
Before disclosing anything — not even the hash — consult a patent attorney in your country. The seal does not replace the patent: it is supporting evidence of your dated priority.