Duplicate Detective scans your files and folders to find duplicates via the following steps:
1) First the app generates a pool of files to scan. The pool is determined by the folders you select to scan and will contain all files that are 50kb or larger in size (you can change this value in the app's preferences, but 50kb is set as default to provide a reasonable scan time).
2) Once the scan pool is generated, the app then compares the unique hash value for each file. Identical files (even if they have different file names) will have exactly the same hash value, which will confirm to the app that the files are duplicates of each other. Please note that just because an image looks like it has a totally identical duplicate, it may still not be reported as a duplicate as the image meta data may be different, thus resulting in a mis-match between the two image hash values.
3) Once the app has compared all the files against one another, it will then generate a list of results that show all the duplicate files and folders it has found, allowing you to easily remove the duplicates and just keep one copy of the file in order to free up disk space.