Securely prove your file's existence at a specific time. Upload your file to generate an OpenTimestamps proof (.ots) anchored to the Bitcoin blockchain.
We calculate a SHA-256 hash locally in your browser. Your file never leaves your device.
The file's hash is submitted to OpenTimestamps calendar servers to create a cryptographic proof.
Your timestamp proof is aggregated and eventually anchored into the Bitcoin blockchain for immutability.
Using the downloaded .ots file and your original file, you can independently verify the timestamp.