Nothing you type leaves your device. The tools compute in your browser. What you enter is kept in your browser’s own storage so a page remembers your inputs; every tool has a “Reset and clear” control that removes it.
Share links carry only the card and the amounts you entered, nothing else; anyone with the link sees the same scenario.
No cookies of our own and no advertising trackers. Fonts are served from this site, not from a third party. If the site adds a privacy-respecting visit counter, it will receive page views only, never entered amounts, and this page will say so.
Links to YouTube and to issuers’ pages take you to those sites, where their own privacy policies apply.