Free Mac app
Fetches your duplicate files. Frees your drive.
Good Boy Duper sniffs out exact copies of your videos, photos, music and documents across any folders or drives, then carries the extras to the Trash. One copy of everything is always kept.
How it works
Three steps. Nothing is erased.
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Point him at some folders
He sniffs out exact copies
You decide. He carries.
Drag in folders or whole drives. Choose what to look for: videos, photos and images, audio, documents, or everything.
Files are matched by size first, then by their actual contents, so only true byte-for-byte copies count. Every drive is read at once, with live progress and time remaining.
Review each set, then one click moves the extras to the Trash. They stay there until you empty it, and you can put everything back, even after relaunching the app.
Why this one
Built by someone who was tired of the other ones.
Most duplicate finders are cluttered, pushy, or quietly dangerous.
This one does a single job carefully.
Exact copies only
A re-encoded or edited file never gets matched with its original. If he says two files are the same, they are the same, down to the last byte.
Trash, never delete
Nothing is erased. Extras go to the macOS Trash and can be put back with one click, even after you have quit the app.
Picks the keeper sensibly
Keep the copy in your main folder, the oldest, or the one with the cleanest name. Override any set with a click. One copy is always kept.
Any kind of file
Videos by default. Switch to photos and camera RAW, audio, documents, or everything on the drive.
Built for big drives
Reads every drive at the same time, shows time remaining, keeps what it found if you cancel, and skips Time Machine and system folders on its own.
Private by design
Sandboxed by macOS. It only sees the folders you add, never connects to the internet, and has no account, analytics or tracking.
Donations
Good boys work for treats.
Good Boy Duper is free. If he reclaimed some space for you, a small donation keeps updates coming and the treat jar full.
One-time, any amount. No perks, no newsletter. Just a thank-you and a wagging tail.
Download Good Boy Duper
Version 1.2 · Free. macOS 14 Sonoma or later, Apple silicon and Intel.
Open the download, drag the app to Applications, and you are set.
Questions
Things people ask before letting a dog near their files.
Will it delete anything?
No. Extra copies are moved to the macOS Trash, exactly as if you had dragged them there yourself. Nothing is freed until you empty the Trash, and until then every file can be put back from inside the app.
What counts as a duplicate?
Two files with identical contents, byte for byte. A video you exported twice at different settings, or a photo you edited, is a different file and will not be matched. That is on purpose: “looks similar” is a judgment call, and this app only makes calls it can be certain about.
Can it scan a single folder, or a whole drive?
Both. Add one folder to find copies inside it, or several folders and drives to find copies across them. Folders inside other folders you have added are only counted once.
Does it need an account or send anything anywhere?
No account, no sign-in, no network. It runs inside the macOS sandbox and only sees the folders you add. The folders you choose are remembered between launches so you do not have to add them again.
Why does a video show “No preview”?
macOS could not decode that format for a thumbnail. Some .avi containers and some 8K or VR encodes do this. The comparison is still exact, and Quick Look or VLC may still play the file.
Which Macs does it run on?
Any Mac running macOS 14 Sonoma or later, Apple silicon or Intel.
Why is it free?
It was built to clean up one person’s own backup drives, and it turned out other people had the same mess. Donations cover the Apple developer fees and the time to keep it working on new versions of macOS.