What is the Daemon Containers folder on a Mac, and what are the long ID folders inside?

What is Daemon Containers?

Apps from the App Store keep their data in ~/Library/Containers, one folder per app, named after the app. Daemon Containers is the same idea for macOS's own background services: each sandboxed service that runs as you gets a private folder, and they are named with an ID instead of a name. They belong to macOS, not to apps you installed.

How big is it?

How do I tell which service a folder belongs to?

Each folder holds a hidden metadata file, .com.apple.containermanagerd.metadata.plist, that names the service. Reading it needs Full Disk Access for Terminal:

cd ~/Library/Daemon\ Containers
for d in */; do
  plutil -extract MCMMetadataIdentifier raw "$d.com.apple.containermanagerd.metadata.plist" 2>/dev/null
done

Is it safe to delete?

No good comes of it. These are live services' working folders, macOS recreates them, and deleting one can reset whatever that service remembered. At 183 MB it is rarely the reason a disk is full. If one folder is many gigabytes, identify it first with the command above, then deal with the service it belongs to.

Find what is left in one look

Free Mac measures Daemon Containers with everything else in Library, which Terminal cannot do without Full Disk Access, and shows the big ones to scale. Compare Containers and what is safe to delete in Library.

Related: ~/Library/Python and IntelligencePlatform.