Background Processing

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 App.init().

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; earliestBeginDate is only a lower-bound hint.

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. They run while the device is idle and can require external power; the same earliestBeginDate lower-bound rule applies.

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()

    let cleanupTask = Task {
        do {
            try await DatabaseManager.shared.purgeExpiredRecords()
            try await DatabaseManager.shared.rebuildIndexes()
            task.setTaskCompleted(success: true)
        } catch {
            task.setTaskCompleted(success: false)
        }
    }

    task.expirationHandler = {
        cleanupTask.cancel()
        task.setTaskCompleted(success: false)
    }
}

BGContinuedProcessingTask (iOS 26+)

A task initiated in the foreground by a user action that continues running in the background. The system displays progress via a Live Activity. Conforms to ProgressReporting.

Availability: iOS 26.0+, iPadOS 26.0+

Unlike BGAppRefreshTask and BGProcessingTask, this task starts immediately from the foreground. The system can terminate it under resource pressure, prioritizing tasks that report minimal progress first. Set expirationHandler for user or system cancellation, cancel in-flight work, and clean up partial output before reporting completion.

import BackgroundTasks

func startExport() {
    // Register the task handler at app launch, not here.
    // BGTaskScheduler requires registration before app launch completes.
    let jobID = UUID().uuidString
    let request = BGContinuedProcessingTaskRequest(
        identifier: "com.example.app.export.\(jobID)",
        title: "Exporting Photos",
        subtitle: "Processing 247 items"
    )
    // Use a permitted base wildcard identifier: com.example.app.export.*
    // earliestBeginDate is ignored for continued processing requests.
    // .queue: begin as soon as possible if can't run immediately
    // .fail: fail submission if can't run immediately
    request.strategy = .queue

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

func performExport(task: BGContinuedProcessingTask) async {
    let items = await PhotoLibrary.shared.itemsToExport()
    let progress = task.progress
    progress.totalUnitCount = Int64(items.count)

    for (index, item) in items.enumerated() {
        if Task.isCancelled { break }

        await PhotoExporter.shared.export(item)
        progress.completedUnitCount = Int64(index + 1)

        // Update the user-facing title/subtitle
        task.updateTitle(
            "Exporting Photos",
            subtitle: "\(index + 1) of \(items.count) complete"
        )
    }

    task.setTaskCompleted(success: !Task.isCancelled)
}

For GPU work, check support and enable Background GPU Access (com.apple.developer.background-tasks.continued-processing.gpu):

let supported = BGTaskScheduler.supportedResources
if supported.contains(.gpu) {
    request.requiredResources = .gpu
}

Background URLSession Downloads

Use URLSessionConfiguration.background for downloads that continue even after the app is suspended or terminated. The system handles the transfer out of process.

class DownloadManager: NSObject, URLSessionDownloadDelegate {
    static let shared = DownloadManager()