How does it know two files are duplicates?

It groups files by size, then compares their contents with SHA-256. Only files whose contents match exactly are listed as exact copies; similar photos are listed separately.

Will it delete my only copy?

No. Every set keeps at least one copy, you see where each lives before anything moves, and removed copies go to the Trash, where Undo Cleanup can restore them.

Does it search external drives?

It scans your home folders. Files in the Photos library are better handled by Photos’ own Duplicates album.

Every feature is free for 14 days, then Peekaboo is a one-time purchase per Mac.

Peekaboo · Duplicate finder

Find duplicate files on your Mac, and undo the cleanup

Copies pile up: the same PDF downloaded twice, a photo exported three times, a project folder duplicated “just in case”. Peekaboo finds them across your home folders and lets you decide, copy by copy, what goes.

Download free trial14 days free · macOS 14+ · Updated November 3, 2026

What it does

Exact copies, proven: Files of the same size are compared by their contents with SHA-256, so two files only count as duplicates when every byte matches. Names don’t matter.
Photos that look alike: Similar Photos groups edits, exports and burst shots that aren’t identical files, using Apple Vision on your Mac. You pick the best one.
You choose what stays: Each set shows every copy and where it lives. Mark the copies to keep and to trash, or Trash All Extras when you trust the set.
One click puts it back: Removed copies go to the Trash as one recorded cleanup. Undo it with ⌥⌘Z, or later from the Undo history. iCloud-only files are skipped, so nothing downloads behind your back.

How to use it

1Open Duplicates.⇧⌘I
2Review Exact Copies, then Similar Photos, marking what to keep.
3Move the extras to the Trash. Changed your mind? Put them back.⌥⌘Z

When another app fits better

If your duplicates live inside the Photos library, Photos’ own Duplicates album merges them safely for free. If you’d rather keep every copy in place and only reclaim the space, [Hyperspace](/alternatives/hyperspace/) turns identical files into APFS clones. Peekaboo is for clearing the copies out, with a way back.

Questions

How does it know two files are duplicates?: It groups files by size, then compares their contents with SHA-256. Only files whose contents match exactly are listed as exact copies; similar photos are listed separately.
Will it delete my only copy?: No. Every set keeps at least one copy, you see where each lives before anything moves, and removed copies go to the Trash, where Undo Cleanup can restore them.
Does it search external drives?: It scans your home folders. Files in the Photos library are better handled by Photos’ own Duplicates album.
Is it free?: Every feature is free for 14 days, then Peekaboo is a one-time purchase per Mac.