DiskFerret identifies duplicate files by comparing one or more of the following; name, size, date, or CRC-32. You can specify the criteria you prefer in the Duplicate File Options dialog, accessed via the Tools > Options – Duplicate Files tab. When CRC-32 is specified, DiskFerret will 1st use other criteria, if specified, to identify duplicate files. When it finds 2 files where the name, size or date matches, it reads both files and computes a 32 bit cyclic redundancy check (CRC-32) for each of them. Don’t worry if you don’t know what a CRC algorithm does, most people don’t. It is a commonly used technique used in software to detect differences in data streams. The CRC algorithm is very fast, however reading the files from disk is relatively slow in comparison, and reading the files from disk takes a lot longer that DiskFerret’s normal scan task of getting the name, size and date from the file system.
Computing CRC’s can take an especially long time if DiskFerret finds many files to compare (i.e., files with the same name, date, or size), or if you specify CRC as the only criteria, which will cause every file’s CRC to be computed (not recommended unless you have a special need). DiskFerret’s recommended defaults are name and size, which is sufficient for most duplicate file identification.