While the preview is open, the captured region is held in temporary session storage in your browser. It is cleared when the browser closes. ProofStamp does not keep a library of your captures.
The PDF or PNG you save goes to your Downloads folder.
Your settings (default format, 12- or 24-hour time, credit line on PDFs).
If you buy a license: your license key, its status and when it was last checked, plus a count of free captures used.
ProofStamp runs only on the tab you are looking at, and only after you click Capture. It captures the visible part of that tab and reads the page title and address to print them on the file. It does not read other tabs, your browsing history or form contents.
When you activate a purchased license, and then about every 14 days to confirm it is still valid, the extension sends your license key and the product ID to Gumroad’s license-verification service (https://api.gumroad.com/v2/licenses/verify). That request is the only network call the extension makes. Like any web request, Gumroad also receives your IP address. Gumroad’s privacy policy applies to that request: https://gumroad.com/privacy. If you never buy a license, the extension makes no network requests at all.
No analytics, tracking or telemetry.
No accounts, sign-ins, cloud sync or sharing.
We do not collect, sell, rent or share your data. Your captures are never sent to us or anyone else.
No ads.
activeTab: Lets ProofStamp capture the tab you are on, only after you click it.
scripting: Shows the region-selection overlay on that tab.
downloads: Saves the PDF or PNG to your Downloads folder.
storage: Saves your settings and license status, and holds the capture while the preview is open.
Access to api.gumroad.com: Used only for the license check described above.
Capture times come from your computer’s clock. ProofStamp is a convenience tool for documenting what a page showed. It does not independently verify, certify or notarise anything.
Purchases are processed by Gumroad, Inc. ProofStamp never sees or stores your payment details.
Uninstalling ProofStamp deletes everything it stored in your browser. Files you saved to your Downloads folder stay where you put them.
If this policy changes, the new version is posted on this page with a new effective date.
Questions: onceworks.tools@gmail.com
Effective date: 17 October 2026
ProofStamp is a browser extension by OnceWorks for Chrome and Firefox. It is built so that your captures stay on your computer.