Free · Browser-side hashing
Stamp & Generate OTS
File contents never leave your browser. SHA-256 is computed locally, then the hash and displayed filename label are submitted to the public API to generate an OpenTimestamps proof file.
Drop a local file here or choose a file from this device
The file is read and hashed in this browser — file contents are not uploaded.
Stamp Created
Proof ID:
Hash:
Tip: the download URL remains available for a limited time. Save files locally.
How it works: Your file's SHA-256 fingerprint is computed locally in a browser worker that reads the file in small chunks. The hash and the displayed filename label are sent to
Verify: Use the Verify page or standard OpenTimestamps tools to independently verify any
/api/v1/public/stamps; file contents never leave your browser. The filename becomes public proof metadata, so rename sensitive files before submitting. The server generates an OpenTimestamps proof and returns a downloadable .ots file. Rate limit: 20 creation requests per 4-hour window per IP.
Verify: Use the Verify page or standard OpenTimestamps tools to independently verify any
.ots file.