Is it safe to delete the Application Support folder on Mac?

No, not the folder itself. ~/Library/Application Support is where almost every app on your Mac keeps its data and settings, so deleting it would reset or break many apps at once. Individual subfolders are another matter: those left behind by apps you've uninstalled are usually safe to delete, and that's often where gigabytes hide.

Quick verdict:

• The Application Support folder itself: never delete it.
• Subfolders of apps you've uninstalled: usually safe to delete.
• Subfolders of apps you still use: only if you accept losing their settings and local data. Prefer the app's own cleanup options.
• Apple's subfolders (AddressBook, CallHistoryDB, com.apple.* and similar): leave them alone.
• MobileSync: holds iPhone and iPad backups. Manage them from Finder.

What is the Application Support folder?

Apple's developer guidelines describe Application Support as the place for an app's support files: data it needs, databases, plug-ins, downloaded resources and so on, each in a subfolder named after the app (Apple: The Library Directory). There are two of them:

• ~/Library/Application Support: your own, in your home folder. This is the big one.
• /Library/Application Support: shared by all users. It mostly holds plug-ins, helpers and licensing files, and needs an admin password to change.

The ~/Library folder is hidden. To open it, in Finder choose Go → Go to Folder (Shift-Command-G) and type ~/Library/Application Support.

It grows because macOS has no real uninstaller. When you drag an app to the Trash, its folder in Application Support stays behind. Apps you use every day also keep adding data: chat histories, browser profiles, downloaded content, caches that the developer chose to put here instead of in ~/Library/Caches.

Big subfolders you're likely to find

Not everything lives here. Sandboxed apps from the App Store keep their data in ~/Library/Containers, and apps that share data between them use Group Containers. Xcode keeps its large data in ~/Library/Developer, not here; see Command Line Tools for that.

How much space does it use?

With Finder. Go to ~/Library, select Application Support and choose File → Get Info. For a size per app, open it in list view, choose View → Show View Options and tick Calculate all sizes.

With Terminal. This lists the twenty biggest subfolders:

du -sh ~/Library/Application\ Support/* 2>/dev/null | sort -rh | head -20

With System Settings. System Settings → General → Storage doesn't show Application Support as such. Most of it is counted under System Data or the app's own category, so it won't tell you which app is responsible.

With SquirrelDisk. SquirrelDisk is a free disk space analyzer. Click A folder, press Shift-Command-G and type ~/Library/Application Support. The chart shows every app folder by size, and you can click into, say, Steam to see which game takes the space. From Terminal, squirreldisk scan ~/Library/Application\ Support --depth 1 --top 15 prints the biggest folders without opening a window.

How to delete it safely

Use the app first

For apps you still use, their own settings are the safest way to free space:

• iPhone backups: connect your iPhone or iPad, select it in the Finder sidebar, click Manage Backups in the General tab, then right-click an old backup and choose Delete (Apple's steps).
• Steam: uninstall games from your Steam library. Steam removes the files and keeps your cloud saves.
• Browsers: clear cached images and files from the browser's settings.
• Adobe apps: use the media cache options in the app's settings.

Remove leftovers of uninstalled apps

1. Make sure the app is gone. Check /Applications and Launchpad. If the app is still installed, quit it (Command-Q) first.
2. In Finder, go to ~/Library/Application Support and find the folder named after the app or its developer.
3. Check what's inside. Look for anything you might want: exported files, game saves, local notes, databases. Copy them elsewhere if in doubt.
4. Drag the folder to the Trash. Repeat for ~/Library/Caches, ~/Library/Preferences (files named like com.developer.app.plist) and ~/Library/Containers if you want a complete clean-up.
5. Use your Mac for a few days before emptying the Trash.

In SquirrelDisk, drag the app's folder into the collector and choose Move to Trash, or Back up to a folder first if you're not sure. SquirrelDisk never lets you delete ~/Library itself, and asks for an extra confirmation for anything inside it.

What you lose, and what not to delete

Deleting an app's folder in Application Support resets that app. Depending on the app, you may lose:

• Settings and sign-ins.
• Local data: chat history that isn't synced, offline files, local databases, notes stored only on your Mac.
• Game saves that aren't backed up by Steam Cloud or the game's own cloud sync.
• Licences for some paid apps, which you'd need to activate again.

Never delete:

• The Application Support folder itself, in ~/Library or /Library.
• Apple's folders: AddressBook (your contacts), CallHistoryDB, CloudDocs (iCloud Drive's sync data), com.apple.TCC (privacy permissions) and the other com.apple.* folders.
• Folders of apps you still use, unless you know what's inside or the app's developer tells you to.

If something breaks, restore the folder from the Trash (right-click → Put Back) or from your Time Machine backup.