Clean junk files on your Mac: caches, logs and developer leftovers

What is junk on a Mac, and is it safe to delete?

Apps write a lot of files they don't strictly need. A cache is a copy of something an app could fetch or rebuild, kept so it opens faster next time. Logs record what an app did. Mail keeps a copy of every attachment you open. Xcode keeps build output for every project you have built. None of it is your work, and most of it comes back by itself when it is needed.

So is it safe to delete caches on a Mac? Generally yes: an app whose cache is cleared rebuilds it, and the worst you notice is that the app is a little slower the first time. What isn't safe is guessing. Old downloads may be the only copy of something, an iOS backup may be the only backup of a phone, and Xcode archives hold the symbols you need to read a crash report. That is why the Junk Cleaner treats those categories differently from caches.

Why "System Data" on your Mac is so large

When System Settings shows a big grey System Data bar under storage, much of it is exactly this kind of file: caches and logs in your Library folder, app data, developer files, and local Time Machine snapshots. macOS doesn't list them for you. The Junk Cleaner does, folder by folder, with a size next to each. For everything else that fills the disk, the Disk Map shows where the space goes.

What the Junk Cleaner finds

Every category is listed with its size and where it lives. The safe ones are ticked when a scan finishes. The others are marked Risky and stay unticked until you choose them. Categories with nothing in them are hidden.

Old installers, matched to the apps you have

A downloaded .dmg or .pkg is useless once its app is installed, yet it often stays in Downloads for years. Tidy My Mac looks at the disk images, packages and archives sitting directly in Downloads and on the Desktop and matches them to the apps in your Applications folders by name, by the macOS installer receipt, and by the site they were downloaded from. Installers whose app was installed after the download are ticked. Weaker matches go to Installers to Check, and each one says why it was matched. Disk images are never mounted to look inside, and files in subfolders are left alone.

Developer junk: delete Xcode DerivedData, simulators, Homebrew and Docker

On a developer's Mac the biggest junk is often build output. Deleting Xcode DerivedData is safe and is the usual first fix when Xcode misbehaves; it is rebuilt on the next build. Old simulator caches, package-manager caches, and the node_modules folders, Python virtual environments and Rust target folders of projects you haven't opened in months add up quickly too. A project counts as untouched only if nothing in it, apart from the folder being offered, changed in 90 days. Conda environments belong to no project, so one counts as unused when nothing has been installed into it for 90 days; the base environment is never offered. JetBrains IDEs and Android Studio keep a settings and plugins folder for every version you update from; the ones unused for 90 days are ticked, and the newest version of each IDE is never touched.

Four categories are cleaned by the tool that owns them rather than by moving files: unavailable simulators and unused simulator runtimes with simctl, old Homebrew versions with brew cleanup, and Docker with docker system prune. Docker volumes are always kept, because they hold the data your containers keep between runs. Simulator runtimes count as unused after 90 days, and the newest runtime for each platform is always kept. Each of these only appears when the tool is installed and has something to clean.

See every file, then decide

Click any category to see every file in it, with its size, date and path, and move just the ones you pick to the Trash. Before a clean, the confirmation says how much goes to the Trash, where you can still restore it, and names anything that doesn't:

Everything else that goes to the Trash is recorded in the cleanup history on the Dashboard, where you can Put Back items. Bear in mind that macOS only frees the space of trashed files when you empty the Trash.

One scan, four sections

Pressing Scan runs one pass over your disk that fills the Junk Cleaner, Large Files, Disk Map and Duplicates at the same time. It runs on your Mac and nothing about your files is sent anywhere; the Privacy Policy has the details.

Full Disk Access

Old Downloads and the installer categories need to read Downloads and the Desktop, which macOS protects. Until you grant Full Disk Access, the Junk Cleaner leaves those folders out instead of raising a macOS prompt for each, and shows a banner that takes you to the setting.