Appmigrationkit

AppMigrationKit

One-time cross-platform data transfer for app resources. Enables apps to export data to or import data from another platform (for example, Android) during device setup or onboarding. AppMigrationKit APIs are iOS 26.0+ / iPadOS 26.0+; the data-container entitlement is iOS 26.1+ / iPadOS 26.1+ / Mac Catalyst 26.1+. Swift 6.3.

Beta-sensitive. AppMigrationKit is new in iOS 26 and may change before GM. Re-check current Apple documentation before relying on specific API details.

AppMigrationKit uses an app extension model. The system orchestrates the transfer between devices. The app provides an extension conforming to export and import protocols, and the system calls that extension at the appropriate time. The app itself never manages the network connection between devices.

Contents

• Architecture Overview
• Setup and Entitlements
• App Migration Extension
• Exporting Resources
• Importing Resources
• Migration Status
• Progress Tracking
• Testing
• Common Mistakes
• Review Checklist
• References

Architecture Overview

AppMigrationKit operates through three layers:

1. App extension -- An AppMigrationExtension conforming type that the system invokes during migration. It handles data export and import.
2. System orchestration -- The OS manages the device-to-device session, transport, and scheduling. The extension does not control when it runs.
3. Containing app -- After migration completes, the app checks MigrationStatus.importStatus on first launch to determine whether migration occurred and whether it succeeded.

Key types:

Setup and Entitlements

Entitlement

The app extension requires the com.apple.developer.app-migration.data-container-access entitlement. Its value is a single-element string array containing the bundle identifier of the containing app:

<key>com.apple.developer.app-migration.data-container-access</key>
<array>
    <string>com.example.myapp</string>
</array>

No other values are valid. This entitlement grants the extension read access to the containing app's data container during export and write access during import. The entitlement itself is available on iOS 26.1+, iPadOS 26.1+, and Mac Catalyst 26.1+, even though the core AppMigrationKit APIs are available on iOS 26.0+ and iPadOS 26.0+.

Extension Target

Add a new App Extension target to the Xcode project. The extension conforms to one or more of the migration protocols (ResourcesExportingWithOptions, ResourcesExporting, ResourcesImporting).

App Migration Extension

The extension entry point conforms to AppMigrationExtension. During migration, the system prevents launching the containing app and its other extensions to ensure exclusive data access.

Accessing the Data Container

The extension accesses the containing app's files through appContainer:

import AppMigrationKit

struct MyMigrationExtension: ResourcesExporting {
    var resourcesSizeEstimate: Int { estimateTotalExportSize() }
    var resourcesVersion: String { "1.0" }
    var resourcesCompressible: Bool { true }

    func exportResources(
        to archiver: sending ResourcesArchiver,
        request: MigrationRequest
    ) async throws {
        let container = appContainer

        // container.bundleIdentifier     -- app's bundle ID
        // container.containerRootDirectory -- root of the app container
        // container.documentsDirectory    -- Documents/
        // container.applicationSupportDirectory -- Application Support/
    }
}

MigrationDataContainer provides containerRootDirectory, documentsDirectory, and applicationSupportDirectory as URL values pointing into the containing app's sandbox.

Exporting Resources

Conform to ResourcesExportingWithOptions (or ResourcesExporting for no custom options) to package files for transfer. The system calls exportResources(to:request:) with a ResourcesArchiver and a MigrationRequestWithOptions.

Declaring Export Properties

struct MyMigrationExtension: ResourcesExportingWithOptions {
    typealias OptionsType = MigrationDefaultSupportedOptions

    var resourcesSizeEstimate: Int {
        // Return estimated total bytes of exported data
        calculateExportSize()
    }

    var resourcesVersion: String {
        "1.0"
    }

    var resourcesCompressible: Bool {
        true  // Let the system compress during transport
    }
}

• resourcesSizeEstimate -- Estimated total bytes. The system uses this for progress UI and free-space checks.
• resourcesVersion -- Format version string. The import side receives this to handle versioned data formats.
• resourcesCompressible -- When true, the archiver may compress files during transport.

Implementing Export

func exportResources(
    to archiver: sending ResourcesArchiver,
    request: MigrationRequestWithOptions<MigrationDefaultSupportedOptions>
) async throws {
    let docsDir = appContainer.documentsDirectory

    // Check destination platform if needed
    if request.destinationPlatform == .android {
        // Platform-specific export logic
    }

    // Append files one at a time -- make continuous progress
    let userDataURL = docsDir.appending(path: "user_data.json")
    try await archiver.appendItem(at: userDataURL)

    // Append with a custom archive path
    let settingsURL = docsDir.appending(path: "settings.plist")
    try await archiver.appendItem(at: settingsURL, pathInArchive: "preferences/settings.plist")

    // Append a directory
    let photosDir = docsDir.appending(path: "photos")
    try await archiver.appendItem(at: photosDir, pathInArchive: "media/photos")
}

The archiver streams files incrementally. Call appendItem(at:pathInArchive:) repeatedly as each resource is ready. The system may terminate the extension if it appears hung, so avoid long gaps between append calls.

Cancellation

ResourcesArchiver handles task cancellation automatically by throwing cancellation errors. Do not catch these errors -- doing so causes the system to kill the extension.

Migration Platform

MigrationRequestWithOptions exposes destinationPlatform as a MigrationPlatform value. Use this to tailor exported data:

if request.destinationPlatform == .android {
    // Export in a format the Android app expects
}

MigrationPlatform provides .android as a static constant. Custom platforms can be created with MigrationPlatform("customPlatform").

Importing Resources

Conform to ResourcesImporting to receive transferred files on the destination device. The system calls importResources(at:request:) after app installation but before the app is launchable.

struct MyMigrationExtension: ResourcesImporting {
    func importResources(
        at importedDataURL: URL,
        request: ResourcesImportRequest
    ) async throws {
        let sourceVersion = request.sourceVersion