What can you safely delete on a Mac?

The honest answer to what can I delete on a Mac is a short, boring list, not a magic button. The rule underneath it is simple: prefer things that regenerate or were disposable to begin with, and when you're not sure, leave it. Here's the master list, sorted into three tiers, with the exact location of everything on it.

Safe: what you can delete on a Mac without thinking twice

Everything here either rebuilds itself or was disposable the moment you were done with it.

• The Trash. Nothing is actually freed until you empty it. Turn on automatic emptying after 30 days in System Settings → General → Storage so it stops quietly holding space.
• Old Downloads (~/Downloads). The .dmg and .pkg installers you've already run are disposable. You can re-download them if you ever need them again.
• User caches (~/Library/Caches). Safe to clear for apps you're not actively using. macOS and the app rebuild what they need on the next launch; the only cost is a slower first load. Leave the system caches under /System/Library alone. For the full rundown, see is it safe to delete cache on a Mac.
• Old iOS/iPadOS backups (~/Library/Application Support/MobileSync/Backup/). Each one can be tens of GB, and they pile up across old devices. Delete them from Finder → the device → Manage Backups (the folder names are unlabeled hashes, so don't delete by hand), and keep your most recent backup. See is it safe to delete iOS backups.
• App leftovers after uninstalling. Dragging an app to the Trash removes only the .app bundle. Its Application Support, Preferences, Caches, Containers, Logs, and launch agents stay behind in ~/Library. Clearing those for apps you no longer have is safe; they belong to software that's already gone.
• Developer build artifacts. node_modules, Xcode DerivedData (~/Library/Developer/Xcode/DerivedData), and Docker's build cache all regenerate from your source and lockfiles. Delete them freely on old projects. See is it safe to delete node_modules.

Caution: only once it's backed up

This tier is real data, irreplaceable if you get it wrong. Deleting is fine, but only when you're certain a copy exists somewhere else.

• Large media in Photos and ~/Movies. Video is the real space hog. Move big libraries and projects to an external drive and verify the copy before deleting the original. iCloud Photos with "Optimise Mac Storage" keeps your originals in iCloud while thinning the local copies.
• Mail attachments. Mail re-downloads them from the server on demand, and local copies live under ~/Library/Containers/com.apple.mail/ (verify the exact path on your macOS version). Safe to clear with Mail closed, but only while the account is still active.
• Big files in ~/Documents. Old archives, disk images, exports. Fine to remove once backed up. These are exactly the things you'll miss if you're wrong, so treat them accordingly.

The dividing line for this tier is one question: is there another copy? If yes, delete. If no, back it up first, then delete.

Never: what macOS owns

Nothing here is worth the risk. The space you'd reclaim is tiny or temporary, and the downside is a broken system.

• /System: the operating system itself. Off limits.
• System files in /Library: shared support files that macOS and your apps depend on.
• Anything macOS manages for itself: the internals behind System Data, purgeable space, and APFS snapshots. macOS thins these on its own when space runs low; hand-deleting them risks removing a needed backup or snapshot for near-zero durable gain. (If you want to understand what that catch-all actually holds, see the hidden storage on your Mac.)
• Other users' folders (/Users/<someone-else>). Not yours to clean.

The one principle that keeps you safe

Strip away the lists and it comes down to a single habit: prefer things that regenerate. A cache, a build folder, an installer you've already run: delete it and nothing is really lost. Documents, photos, the only copy of anything: treat as sacred until you've confirmed a backup. And the moment you can't tell which pile something belongs in, don't delete it. The downside of keeping a file you didn't need is a few gigabytes. The downside of deleting one you did is unrecoverable.

Worth saying plainly. The space you win back from caches is temporary. They rebuild. macOS also clears safe-to-delete caches and logs on its own when the disk gets tight, so scrubbing them by hand is a treadmill, not a fix. For the full walkthrough of reclaiming space in the right order, see how to free up space on a Mac.

Doing all of this by hand means memorizing which ~/Library folders rebuild and which don't, hunting leftovers across a hidden directory, and hoping you never drag the wrong thing to the Trash. Plumby only ever acts on an allowlisted set of the safe things above (regenerable caches and build artifacts), and never your documents, photos, or projects. It shows the exact path of everything before it touches it, measures the space it actually frees, and acts only on your command. You can send what it clears to the Trash rather than delete it, so a wrong call stays recoverable.