App Group Container
Also known as: app groups ios, shared container, ios app group container
An App Group container is a shared on-disk directory and preferences domain that lets an iOS app, its extensions, and related apps from the same developer read and write the same files outside their individual sandboxes.
- App Groups share one directory and a UserDefaults suite across an app and its extensions.
- Access uses FileManager.containerURL(forSecurityApplicationGroupIdentifier:) with a group. entitlement.
- Data in the shared container counts toward the app's size in iPhone Storage settings.
What an App Group container is
iOS apps are sandboxed, so each app and each extension normally gets its own private container that nothing else can read. An App Group punches a controlled hole in that wall: apps and extensions that declare the same group identifier (the `group.` prefix entitlement) gain access to one shared container directory plus a shared UserDefaults suite.
Code reaches the directory through FileManager.containerURL(forSecurityApplicationGroupIdentifier:), which returns the group's root URL. Inside it sit the standard Library, Caches, and document-style folders. The group is enabled in the Signing & Capabilities tab in Xcode and provisioned via the developer account, so only the developer's own targets can join.
What it is used for
App Groups are the standard way to share data between an app and its extensions (widgets, Share, Notification Service, keyboard, Watch, and App Clips). A widget reads the same cached payload the main app wrote; a Share extension drops an imported file where the host app can pick it up.
Because the shared container is real on-disk storage, large cached images, downloaded media, or database files placed there count toward the app's overall footprint. From the user's perspective in Settings > General > iPhone Storage, that space is attributed to the app, even though it physically lives in the group container rather than the app's primary sandbox.
Why a cleaner accounts for it
App Group containers are private to the developer's apps, so a third-party cleaner cannot reach into another app's shared container and delete files. What it can do is help you understand why an app reports a large size: data may be spread across the app sandbox plus one or more group containers and extension caches.
For the user, the practical levers remain the same: clear the app's cache or offload the app to reclaim space, and remove the redundant photos and videos those apps accumulate. Cleanor focuses on that user-reclaimable layer, photos, videos, and duplicates, while the shared container stays under the owning app's control.