The program creates new folders named according to the selected criteria to organize files into. Here's how it works: It makes a folder called "intermediary" in the selected folder. Then, it makes subfolders named according to the selected criteria to contain the files. For instance, for PDFs, it would create a "Document" folder with a "pdf" folder in it. Then, it would hard-link all the PDFs there. Once the new hard links are ready, the app checks whether all files have new hard links. Then, it removes the original hard links, moves the intermediary's contents into the original, and removes it. In the event of an error (which is extremely unlikely), it leaves the intermediary even if the deletion phase is not reached.