Your files
Every tool runs entirely in your browser. Images are decoded, edited and converted on your own device and are never uploaded. The site has no server-side code, no accounts and no database, so there is nothing of yours to store, sell or leak.
Stored in your browser
The site remembers a few settings in your browser's local storage, such as the last device, format and firmware you picked, and your analytics choice. They never leave your device. Clearing this site's data in your browser removes them.
Analytics
If you allow it, Google Analytics counts anonymous page visits and which export settings are used (tool, device, format, dithering, firmware, template and a rough file count). File names, images and anything you type are never sent. Nothing is loaded until you click Accept, and nothing at all when your browser sends Global Privacy Control.
Questions
The site is open source, so you can check all of the above in the code. Questions and reports are welcome as GitHub issues.