Privacy
Shelf Bartender is a static page. It has no accounts, no analytics, no ads and no server of its own.
Everything you change (which bottles are in, low or out, bottles you add, your own recipes, favourites, the made-it log with your ratings and notes, the shopping list and "not buying" choices) is saved in this browser's local storage on this device.
Sync, if you turn it on. Sync sends that same data to a Google Apps Script web app that you own, running in your own Google account, and nowhere else. It is stored there in the script's own storage (Script Properties). A setup link opened once on each device tells the page where your script is and holds a long random key; the page keeps both in this browser's local storage and the script refuses any request without the key. Nobody else, including the author of this page, receives a copy. Google's own privacy terms cover what Google stores for your account. To stop syncing on a device, use "Stop syncing on this device" under More.
"Paste a recipe" reads the text right in the page; it isn't uploaded or sent to any service. "Export" saves a file to your device and "Import" reads one you pick; neither goes over the network.
The page loads its typefaces from Google Fonts, which sees an ordinary font request. Source links on recipes open other sites, which have their own privacy policies.