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A clone is a copy that shares its data with another file instead of taking up space of its own. On most Macs, copying a file in the Finder on the same disk makes a clone. Moving a clone to the Trash frees almost nothing, so Unduped labels clones and leaves them out of the “Really frees” number.

• The Trash. Files in the Trash still take up space. Empty the Trash to get it back.
• Time Machine. If you use it, macOS keeps local snapshots on your Mac, usually for about a day. A snapshot holds on to files until macOS removes it or needs the room.
• Purgeable space. macOS frees some space only when it’s needed, so Finder and System Settings can show different numbers for a while.

Every group keeps at least one copy, and you can’t select the last one. Files go to the Trash; nothing is permanently deleted. Just before moving a file, Unduped checks it again and skips it if it changed since the scan. It never looks inside apps, Time Machine backups, or system folders. It reads your Photos library only if you add it, and never changes it. It never marks files in code projects for you, so a project keeps what it needs to build.

Click Undo on the result screen, or choose a cleanup in Recent Cleanups. Unduped keeps your last 5. Undo works while the files are still in the Trash. You can also open the Trash in Finder and drag any file back out. Once the Trash is emptied, use a Time Machine backup if you have one.

For free, you can scan as much as you like, see every result, and move up to 500 MB of duplicates to the Trash in total. Unduped Unlock removes the limit. It’s a one-time in-app purchase with no subscription, and your family can use it through Family Sharing.

Files in iCloud Drive that are downloaded to your Mac are checked like any other file. Files stored only in iCloud aren’t downloaded or checked, because removing them wouldn’t free space on your Mac. Moving a synced file to the Trash removes it from your other devices too. Undo puts it back.

System folders and your Library folder, the inside of apps and libraries (such as the Music library; the Photos library’s own folder is never scanned), Time Machine backups, the Trash, hidden files, developer folders such as .git and node_modules (and build folders such as build and dist inside code projects), and files under 100 KB. You can change some of these in Settings.

Yes, to find photos and videos on your disks that are already in your library — in Downloads, on your Desktop, on an old disk. Add Photos Library as a source, and those files can go to the Trash while the copy in Photos stays.

Unduped only reads your library and never changes it. It doesn’t download anything from iCloud: if a photo’s original is only in iCloud, Unduped compares it with the preview that’s already on your Mac and leaves the choice to you. Copies on external disks aren’t marked for you, because a disk like that is often a backup.

Duplicates inside the library are Photos’ own job: open Photos and choose Duplicates under Utilities in the sidebar.

It finds builds, caches and old toolchains that developer tools make again by themselves: DerivedData, Gradle and npm caches, old Kotlin/Native versions, build folders in your projects, and similar files for 15 languages and their tools. Each folder shows why it can go and how it comes back.

It never touches your source code, .git folders, keys and settings such as debug.keystore, versions your projects still use, or folders a running tool is using. Simulators, emulators, archives and AI models are your data, so they’re never marked for you.

Files in the Trash still take up space. Unduped moves folders to the Trash instead of deleting them, so you can undo a cleanup or drag a folder back from the Trash in Finder. It never empties the Trash for you.

Once your projects build and run as before, empty the Trash. Folders with many thousands of files can take Finder a few minutes. Afterwards, Unduped shows how much space emptying the Trash actually freed.

Usually it’s Time Machine. If you back up with Time Machine, macOS keeps local snapshots on your Mac for about a day. A snapshot holds on to the files it contains, so their space comes back once macOS removes it. macOS does this on its own, and sooner when your disk is low on space.

Your tools also make some files again as you work: the next build brings back that project’s build folder. That’s expected. Space from projects and versions you no longer use stays free.

Unduped only moves files to the Trash and never runs other tools, which isn’t safe for these:

• Docker keeps every image, container and volume in one disk image.
• Simulator runtimes are system files only Xcode removes, and a simulator removed by hand can stay listed in Xcode.
• Ollama models share their files, so only Ollama knows what removing one frees.

Unduped shows how to free each. Android emulators and Hugging Face or LM Studio models are separate folders: check them under “Your data — review”.

Finding and reviewing developer files is free. You can move up to 5 GB of them to the Trash for free: enough for a large build folder or two, so you can rebuild your projects and check that nothing broke. This is separate from the 500 MB for duplicates. Only space that’s really freed counts, and Undo gives it back.

Unduped Unlock, a one-time purchase, removes both limits. There’s no subscription.