Separate individual photographs from a page that was scanned with several of them on the platen at once. The tool finds the edges of each photo, straightens it and saves it as its own image. Scanning a batch of prints four or six at a time is far quicker than doing them one by one, and this is what undoes that afterwards.
Leave a clear gap between them and keep them roughly square to the edges of the glass. Photos that touch each other tend to be detected as one region.
Detection depends on contrast between the photo edge and the background. Light or white-bordered prints on a white scanner lid are the hard case - closing the lid on a dark sheet of paper helps a great deal.
Yes, each detected region is deskewed as it is cut out, so slightly crooked prints come out square.
Files are uploaded over an encrypted connection and processed on CoonTool's own server, not in your browser. The working copy is deleted automatically once the job is done, and in any case within 24 hours. Nothing is stored permanently and no account is required.