Files stay on the machine
Cinder reads the file where it is and writes the result in the same folder. The original is not uploaded, and it is not copied to the site.
Privacy
What stays, what leaves.
Cinder is a Windows application. No account. No advertising.
An identifier is used for the license
On the first launch, Cinder creates an identifier and saves it in %LOCALAPPDATA%\Cinder\machine.txt on Windows, or in ~/Library/Application Support/Cinder/machine.txt on macOS. It counts the 20 free files and recognizes the €29.99 unlock on this machine. That identifier is sent to https://cinder-app.com when Cinder checks the license. It is not a name. File contents are not included.
Shift, Alt, and Ctrl open the wheel
The gesture watches whether Shift, Alt, or Ctrl is held, so the wheel can appear under the cursor. Cinder does not read the other keys. The gesture is neither recorded nor sent.
Payment opens in the browser
After the 20 files, Cinder opens the site's payment page. Cinder does not see the card. Payment is handled on https://cinder-app.com.