~/Library/Containers is where macOS stores the sandboxed data for every App Store and sandboxed app — preferences, caches, attachments, saved state. It routinely reaches tens of gigabytes, but deleting the folder wholesale is destructive.
Short answer: do not delete the whole Containers folder. You may safely delete individual subfolders that belong to apps you have already uninstalled.
What sandboxing puts in Containers
Sandboxed apps cannot touch arbitrary locations on disk. Instead, macOS gives each one a private folder inside ~/Library/Containers named after its bundle ID (for example com.apple.mail or com.microsoft.Word).
Everything that app needs — settings, cached downloads, attachments, local databases — lives inside that one directory. That is why the folder grows: it is basically the combined working set of every sandboxed app ever installed.
Cleaning Containers without breaking apps
The rule is simple: delete per-app subfolders, never the parent.
- open Finder
- press Command + Shift + G
- paste
~/Library/Containers/and press Enter - sort by Size (use List View + Calculate All Sizes from the folder size guide)
- delete only subfolders whose app has already been uninstalled (check Applications first)
- for apps you still use, clear their cache inside the app itself — never by hand
Deleting the parent folder logs you out of mail accounts, wipes app settings, and can destroy unsaved local data in sandboxed apps.
Better next routes
If hunting folders by hand feels risky, use a visual analyzer — continue with Best Disk Space Analyzer for Mac (Free and Paid).
For the broader "what is taking space" picture, read What is System Data on Mac?.