How a duplicate file finder skips hashing most of your disk using three filters

A common approach to finding duplicate files is to hash every file, but this is slow: a 1.09 GB test folder took about 21 seconds, which would scale to roughly three hours on a 500 GB drive. The solution described is not a faster hash but avoiding reading most bytes at all. Files are first grouped by size using metadata, since files of different sizes cannot be identical, and only size groups with multiple members continue. Remaining candidates are then checked by hashing just their first 4 KB, with full hashing reserved for those that still match. The article also covers handling hard links via inode identifiers and working around Windows path-length limits.