Seal a file

Your file never leaves your device. Your browser computes a SHA3-256 fingerprint and we sign just the fingerprint under our quantum-tier post-quantum keys. The receipt is yours forever — verifiable by anyone, even after quantum computers arrive.

Drop a file here, or click to pick

Files up to ~1 GB. Hashing happens in your browser. We only see the fingerprint.

Declare a creator license

Optional. Bind permission terms — AI training, commercial use, attribution — into the signed receipt. Removing or changing them later breaks the signature.

What this seal does and doesn't prove

It proves: this exact byte sequence existed at this exact moment, signed under our quantum-tier post-quantum keys, recorded at a permanent position in our tamper-evident chain. Any modification breaks the seal — detectable by anyone, forever.

It does NOT prove: who created the file (only that the file existed); that the content is original; that the file is legal or copyrightable; or that you generated it before anyone else generated the same content.

Strongest receipt: seal at the moment of creation, before publishing anywhere else. The earlier the seal, the harder it is for anyone to claim they had it first.