Free · Browser-side hashing

Stamp & Generate OTS

Files never leave your browser. SHA-256 is computed locally, then submitted to the public API to generate an OpenTimestamps proof file.

Upload File

Paste SHA-256

Drop a file here or click to browse

The file is hashed in your browser — nothing is uploaded.

SHA-256 Hash (64 hex characters)

Stamp Created

Proof ID:

Hash:

Download .ots

Tip: the download URL remains available for a limited time. Save files locally.

How it works: Your file's SHA-256 fingerprint is computed in the browser using the Web Crypto API. Only the hash is sent to /api/v1/public/stamps. The server generates an OpenTimestamps proof and returns a downloadable .ots file. Rate limit: 3 stamps per 72 hours per IP.

Verify: Use the Verify page or standard OpenTimestamps tools to independently verify any .ots file.