Background Processing

Register, schedule, and execute background work on iOS using the BackgroundTasks framework, background URLSession, and background push notifications.

Contents

• Info.plist Configuration
• BGTaskScheduler Registration
• BGAppRefreshTask Patterns
• BGProcessingTask Patterns
• BGContinuedProcessingTask (iOS 26+)
• Background URLSession Downloads
• Background Push Triggers
• Common Mistakes
• Review Checklist
• References

Info.plist Configuration

Every task identifier must be declared in Info.plist under BGTaskSchedulerPermittedIdentifiers, or submit(_:) throws BGTaskScheduler.Error.Code.notPermitted.

<key>BGTaskSchedulerPermittedIdentifiers</key>
<array>
    <string>com.example.app.refresh</string>
    <string>com.example.app.db-cleanup</string>
    <string>com.example.app.export</string>
</array>

Also enable the required UIBackgroundModes:

<key>UIBackgroundModes</key>
<array>
    <string>fetch</string>       <!-- Required for BGAppRefreshTask -->
    <string>processing</string>  <!-- Required for BGProcessingTask -->
</array>

In Xcode: target > Signing & Capabilities > Background Modes > enable "Background fetch" and "Background processing".

BGTaskScheduler Registration

Register handlers before app launch completes. In UIKit, register in application(_:didFinishLaunchingWithOptions:). In SwiftUI, register in the App initializer.

UIKit Registration

import BackgroundTasks

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.refresh",
            using: nil  // nil = default background queue
        ) { task in
            self.handleAppRefresh(task: task as! BGAppRefreshTask)
        }

        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.db-cleanup",
            using: nil
        ) { task in
            self.handleDatabaseCleanup(task: task as! BGProcessingTask)
        }

        return true
    }
}

SwiftUI Registration

import SwiftUI
import BackgroundTasks

@main
struct MyApp: App {
    init() {
        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.refresh",
            using: nil
        ) { task in
            BackgroundTaskManager.shared.handleAppRefresh(
                task: task as! BGAppRefreshTask
            )
        }
    }

    var body: some Scene {
        WindowGroup { ContentView() }
    }
}

BGAppRefreshTask Patterns

Short-lived tasks (~30 seconds) for fetching small data updates. The system decides when to launch based on usage patterns.

func scheduleAppRefresh() {
    let request = BGAppRefreshTaskRequest(
        identifier: "com.example.app.refresh"
    )
    request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60)

    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        print("Could not schedule app refresh: \(error)")
    }
}

func handleAppRefresh(task: BGAppRefreshTask) {
    // Schedule the next refresh before doing work
    scheduleAppRefresh()

    let fetchTask = Task {
        do {
            let data = try await APIClient.shared.fetchLatestFeed()
            await FeedStore.shared.update(with: data)
            task.setTaskCompleted(success: true)
        } catch {
            task.setTaskCompleted(success: false)
        }
    }

    // CRITICAL: Handle expiration -- system can revoke time at any moment
    task.expirationHandler = {
        fetchTask.cancel()
        task.setTaskCompleted(success: false)
    }
}

BGProcessingTask Patterns

Long-running tasks (minutes) for maintenance, data processing, or cleanup. Runs only when device is idle and (optionally) charging.

func scheduleProcessingTask() {
    let request = BGProcessingTaskRequest(
        identifier: "com.example.app.db-cleanup"
    )
    request.requiresNetworkConnectivity = false
    request.requiresExternalPower = true
    request.earliestBeginDate = Date(timeIntervalSinceNow: 60 * 60)

    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        print("Could not schedule processing task: \(error)")
    }
}

func handleDatabaseCleanup(task: BGProcessingTask) {
    scheduleProcessingTask()