BA | Stamp

Stamp the current web page on Polygon to prove the URL existed at a specific time.

BA | Stamp is a one-click web-page timestamping tool. Click the toolbar icon on any page, pick PDF or PNG, review the captured file in your viewer, then anchor its SHA-256 hash on the Polygon blockchain. The hash is anchored forever; anyone can verify that the file you have today matches the one stamped at that moment. WHAT IT'S FOR • Journalism — prove a public statement existed before it was edited or taken down. • Intellectual property — prove a design, post, or document existed on this date. • AI provenance — prove what an AI model output looked like at a specific time. • Scam research and audit trails — capture web evidence with cryptographic timestamps. HOW IT WORKS 1. Open any web page and click the BA | Stamp toolbar icon. 2. Choose Full-page PDF (selectable text, every section, URL + timestamp in every footer) or Screenshot PNG (visible viewport with a URL + timestamp banner above the screenshot). 3. Click "Capture & preview". The file is generated locally, saved to your Downloads folder, and opens in your viewer. No credit charged yet. 4. Inspect the file. If it looks right, click "Confirm & anchor (1 credit)". The extension SHA-256s the file and POSTs that hash to the public bastamp.com API. The hash gets anchored on Polygon in the next batch (~5 minutes). 5. If anything looks wrong, click "Cancel & delete file" — the file is removed from Downloads and no credit is charged. WHAT GETS SENT Only the SHA-256 hash of the captured file, the file size, the file name, and the MIME type. THE FILE ITSELF NEVER LEAVES YOUR BROWSER. The page contents are not transmitted, not stored, not analyzed. HOW TO VERIFY A STAMP Visit bastamp.com/verify/<hash> (the popup shows the link after confirming) and drop the captured file on the page. The verify page recomputes the SHA-256 and compares it with the on-chain anchor. You can also compute the hash yourself (sha256sum / certutil) — the open-source verifier at github.com/stamp-verify/stamp-verify confirms the on-chain match without any trust in bastamp.com. PRICING Each confirmed stamp uses one credit from your bastamp.com account. The first stamp on a new account is free; packs available at bastamp.com/pricing. OPEN SOURCE The extension is MIT-licensed. Every line of code is auditable: github.com/stamp-verify/stamp-extension. Read it before installing.