Self-Publishing Calculator (the Chrome extension) and its licence service. Publisher: Donny Automation. Effective November 11, 2026.
The calculators run in your browser on the numbers you type. Your saved books, prices and scenarios are kept in your browser's extension storage (chrome.storage.local) and are never sent to us or anyone else. The extension never reads, stores or fetches any Amazon or KDP page.
Only these three things, and only when you use Pro:
The extension sends the licence key and the install id to our licence service when you activate Pro and about once a week after that, to check that the purchase is still valid.
Stripe is our payment processor. When you click Upgrade, the extension opens our Stripe payment page and adds your install id to the address as client_reference_id, so Stripe passes it to us with the payment. Stripe, not us, collects and processes your card and billing details under its own privacy policy (https://stripe.com/privacy). We never see your card number.
The licence service asks Stripe, with a read-only key, whether a checkout was paid and not refunded or disputed. It keeps that answer in memory for up to 10 minutes. It has no database and writes no files.
The licence service logs the request method, path and status, and a one-way hash of the licence key. It does not log the licence key itself, your install id or your request headers. Our hosting provider (Railway) may keep standard network logs, including IP addresses, for a short time.
We do not sell or share your data. We do not use it for advertising, credit checks or anything other than checking your licence. We use no analytics or tracking in the extension.
Use the developer contact email shown on the Chrome Web Store listing. We answer privacy requests within 30 days.