Duplicate files · Duplicates basics
Why do I have so many duplicate files on my Mac?
Short answer: Duplicates build up from downloading the same file twice, saving an export to Desktop and also filing a copy, re-importing videos, or copying folders before reorganising. Storage Studio lists them largest space-saving first so the big wins come first.
Duplicates build up quietly through everyday use: downloading the same attachment more than once ("file (1).pdf"), saving an export to Desktop and then filing a copy in Documents, importing videos from a phone more than once, or copying a folder "just in case" before reorganising.
None of that is a problem until the copies are large — a few duplicated videos or disk images can take up gigabytes. The Duplicates window lists sets largest space-saving first, so the biggest wins are at the top and you can deal with them in a couple of clicks.