Standard — byte-for-byte or hash match. Music — compares ID3/AAC tags (artist, title, album) with fuzzy tolerance. Picture — compares visual similarity, useful for finding resized or re-saved images.

In music and picture modes, the Filter Hardness slider (1–100) controls how similar files must be to count as duplicates. 100 = exact match only, lower values catch more near-matches.

The first file in each group is the ‘reference’ — it won’t be marked for deletion by default. You can manually change which file is the reference by right-clicking.