/push-notifications

Rich Notifications

Rich notifications enhance the standard notification banner with images, video, audio, custom UI, and interactive elements. They use two extension types: Notification Service Extension (modifies content before display) and Notification Content Extension (provides custom UI in the expanded notification).

Contents

• Notification Service Extension
• Notification Attachments
• Notification Content Extension
• Communication Notifications
• Extension Gotchas
• Complete Service Extension Example

Notification Service Extension

A Notification Service Extension runs for an alerting remote notification whose payload has mutable-content: 1 and an alert dictionary with title, subtitle, or body content. It has approximately 30 seconds to modify the notification content before the system displays it. Call the content handler on every path: success, partial failure, invalid payload, and serviceExtensionTimeWillExpire(). If the extension does not call the handler in time, the system displays the original notification.

When reviewing a flawed rich-notification design, explicitly correct four contracts: silent pushes do not trigger service extensions; attachments must be supported files on disk and are validated and stored by the system; communication notifications require the capability, NSUserActivityTypes, INInteraction donation, and content.updating(from:); every service-extension path, including download/decryption failures and serviceExtensionTimeWillExpire(), must call the content handler exactly once with original, best-attempt, or updated content.

Creating the Extension

In Xcode: File > New > Target > Notification Service Extension. This creates a new target with a NotificationService class.

import UserNotifications

class NotificationService: UNNotificationServiceExtension {
    private var contentHandler: ((UNNotificationContent) -> Void)?
    private var bestAttemptContent: UNMutableNotificationContent?
    private var didComplete = false

    override func didReceive(
        _ request: UNNotificationRequest,
        withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void
    ) {
        self.contentHandler = contentHandler
        bestAttemptContent = request.content.mutableCopy() as? UNMutableNotificationContent

        guard let content = bestAttemptContent else {
            contentHandler(request.content)
            return
        }

        // Modify the notification content here
        Task {
            await processNotification(content: content)
            contentHandler(content)
        }
    }

    /// Called if the extension is about to be terminated (ran out of time).
    /// Deliver the best attempt -- even a partially modified notification
    /// is better than nothing.
    override func serviceExtensionTimeWillExpire() {
        if let handler = contentHandler, let content = bestAttemptContent {
            handler(content)
        }
    }

    private func processNotification(content: UNMutableNotificationContent) async {
        // Download image if URL is provided
        if let imageUrlString = content.userInfo["imageUrl"] as? String {
            await attachImage(from: imageUrlString, to: content)
        }

        // Decrypt body if encrypted
        if let encrypted = content.userInfo["encryptedBody"] as? String {
            content.body = decrypt(encrypted)
        }
    }
}

Downloading Images and Media

Download media from a URL and attach it to the notification. The attachment must be written to disk in the extension's temporary directory.

extension NotificationService {
    private func attachImage(
        from urlString: String,
        to content: UNMutableNotificationContent
    ) async {
        guard let url = URL(string: urlString) else { return }

        do {
            let (data, response) = try await URLSession.shared.data(from: url)

            // Determine file extension from MIME type
            let ext = fileExtension(for: response.mimeType)
            let tempDir = FileManager.default.temporaryDirectory
            let fileURL = tempDir.appendingPathComponent(UUID().uuidString + ext)

            try data.write(to: fileURL)

            let attachment = try UNNotificationAttachment(
                identifier: "image",
                url: fileURL,
                options: nil
            )
            content.attachments = [attachment]
        } catch {
            print("Failed to download notification image: \(error)")
            // Notification displays without the image -- graceful degradation
        }
    }

    private func fileExtension(for mimeType: String?) -> String {
        switch mimeType {
        case "image/jpeg": return ".jpg"
        case "image/png": return ".png"
        case "image/gif": return ".gif"
        case "video/mp4", "video/mpeg4": return ".mp4"
        case "audio/mpeg", "audio/mp3": return ".mp3"
        case "audio/wav": return ".wav"
        default: return ".jpg"
        }
    }
}

Decrypting Encrypted Payloads

Use the service extension to decrypt sensitive notification content. The APNs payload carries an encrypted blob; the extension decrypts it before display.

extension NotificationService {
    private func decrypt(_ encryptedBase64: String) -> String {
        guard let data = Data(base64Encoded: encryptedBase64) else {
            return "New notification"  // fallback
        }
        // Use your encryption library (CryptoKit, etc.) to decrypt
        // Store notification decryption keys in a Keychain access group shared
        // by the app and extension, not in UserDefaults or the APNs payload.
        do {
            let decrypted = try EncryptionService.shared.decrypt(data)
            return String(data: decrypted, encoding: .utf8) ?? "New notification"
        } catch {
            return "New notification"
        }
    }
}

Sharing Data with Extensions

The service extension runs in a separate process from the main app. Use App Groups for shared files and UserDefaults; use Keychain Sharing for secrets or tokens.

1. Enable "App Groups" capability on both the main app target and the extension target.
2. Use the same group identifier (e.g., group.com.example.myapp).
3. Enable "Keychain Sharing" on both targets for shared keychain items. The kSecAttrAccessGroup value must be one of the target's keychain access groups, not the App Group container identifier.

// Shared UserDefaults
let sharedDefaults = UserDefaults(suiteName: "group.com.example.myapp")

// Shared file container
let sharedContainer = FileManager.default.containerURL(
    forSecurityApplicationGroupIdentifier: "group.com.example.myapp"
)

// Shared Keychain: set kSecAttrAccessGroup to a Keychain Sharing access group
// that both targets include in their entitlements.

Extension memory: Notification Service Extensions are memory-constrained. Do not load large frameworks or perform memory-intensive operations. If the system terminates the extension, it shows the original notification.

Notification Attachments

UNNotificationAttachment supports images, GIFs, video, and audio. The system displays a thumbnail in the collapsed notification and the full media in the expanded view.

Supported Formats and Limits

Creating Attachments

// From a local file URL
let attachment = try UNNotificationAttachment(
    identifier: "photo",
    url: localFileURL,
    options: nil
)

// With options for thumbnailing
let attachment = try UNNotificationAttachment(
    identifier: "photo",
    url: localFileURL,
    options: [
        UNNotificationAttachmentOptionsThumbnailClippingRectKey:
            CGRect(x: 0, y: 0, width: 1, height: 0.5).dictionaryRepresentation,
        UNNotificationAttachmentOptionsThumbnailTimeKey: 0  // for video: thumbnail at 0 seconds
    ]
)

// Attach to content
content.attachments = [attachment]

Important: The file URL must point to a supported audio, image, or video file on disk. For service extensions, write downloads to the extension's temporary directory before creating UNNotificationAttachment; do not attach arbitrary remote URLs or unsupported file types. For local notifications, create the attachment from a file the app can read when scheduling. The system validates attachments and moves them into its attachment data store; it copies attachments located inside the app bundle.

Multiple Attachments

You can attach multiple items, but only the first attachment is shown as the thumbnail in the collapsed notification. The expanded view can show all attachments.

content.attachments = [imageAttachment, audioAttachment]
// imageAttachment appears as the thumbnail

GIF Animations

GIF files are supported image attachments and may contain an animated image sequence. Test the expanded notification UI for the actual presentation you need.

let gifURL = tempDir.appendingPathComponent("animation.gif")
try gifData.write(to: gifURL)
let attachment = try UNNotificationAttachment(
    identifier: "animation",
    url: gifURL,
    options: nil
)

Notification Content Extension

A Notification Content Extension provides a custom view controller that displays when the user long-presses (or expands) a notification. Use it for richer UI than attachments alone can provide.

Creating the Extension

In Xcode: File > New > Target > Notification Content Extension. This creates a new target with a storyboard and a NotificationViewController.

Configuration (Info.plist)

The extension's Info.plist must declare which notification categories it handles:

<key>NSExtension</key>
<dict>
    <key>NSExtensionAttributes</key>
    <dict>
        <key>UNNotificationExtensionCategory</key>
        <!-- Use a string for one category, or an array for multiple. -->
        <array>
            <string>MESSAGE_CATEGORY</string>
            <string>PHOTO_CATEGORY</string>
        </array>
        <!-- Optional: size ratio (height / width). Default 1.0 -->
        <key>UNNotificationExtensionInitialContentSizeRatio</key>
        <real>0.5</real>
        <!-- Optional: hide the default notification body below the custom UI -->
        <key>UNNotificationExtensionDefaultContentHidden</key>
        <true/>
        <!-- Optional: allow user interaction in the custom UI -->
        <key>UNNotificationExtensionUserInteractionEnabled</key>
        <true/>
    </dict>
    <key>NSExtensionMainStoryboard</key>
    <string>MainInterface</string>
    <key>NSExtensionPointIdentifier</key>
    <string>com.apple.usernotifications.content-extension</string>
</dict>

View Controller Implementation

import UIKit
import UserNotifications
import UserNotificationsUI

class NotificationViewController: UIViewController, UNNotificationContentExtension {
    @IBOutlet weak var titleLabel: UILabel!
    @IBOutlet weak var bodyLabel: UILabel!
    @IBOutlet weak var imageView: UIImageView!

    func didReceive(_ notification: UNNotification) {
        let content = notification.request.content
        titleLabel.text = content.title
        bodyLabel.text = content.body

        // Display the first attachment
        if let attachment = content.attachments.first,
           attachment.url.startAccessingSecurityScopedResource() {
            defer { attachment.url.stopAccessingSecurityScopedResource() }
            if let data = try? Data(contentsOf: attachment.url) {
                imageView.image = UIImage(data: data)
            }
        }
    }

    /// Called when the user taps a notification action while the content
    /// extension is visible.
    func didReceive(
        _ response: UNNotificationResponse,
        completionHandler completion: @escaping (UNNotificationContentExtensionResponseOption) -> Void
    ) {
        switch response.actionIdentifier {
        case "LIKE_ACTION":
            // Update UI to show "liked" state
            animateLikeConfirmation()
            // Dismiss after a short delay
            Task {
                try? await Task.sleep(for: .seconds(0.5))
                completion(.dismiss)
            }

        case "REPLY_ACTION":
            if let textResponse = response as? UNTextInputNotificationResponse {
                // Handle reply inline without opening the app
                showReplySentConfirmation(text: textResponse.userText)
                Task {
                    try? await Task.sleep(for: .seconds(1.0))
                    completion(.dismiss)
                }
            }

        default:
            // Forward to the app's notification delegate
            completion(.dismissAndForwardAction)
        }
    }
}

Response Options

Media Playback in Notifications

The content extension can play audio or video. Implement mediaPlayPauseButtonType and mediaPlayPauseButtonFrame for a system-provided play/pause button.

class MediaNotificationViewController: UIViewController, UNNotificationContentExtension {
    var player: AVPlayer?

    override var mediaPlayPauseButtonType: UNNotificationContentExtensionMediaPlayPauseButtonType {
        return .overlay  // .none, .default, .overlay
    }

    override var mediaPlayPauseButtonFrame: CGRect {
        return CGRect(x: 0, y: 0, width: view.bounds.width, height: view.bounds.height)
    }

    func mediaPlay() {
        player?.play()
    }

    func mediaPause() {
        player?.pause()
    }

    func didReceive(_ notification: UNNotification) {
        guard let attachment = notification.request.content.attachments.first,
              attachment.url.startAccessingSecurityScopedResource() else { return }

        let playerItem = AVPlayerItem(url: attachment.url)
        player = AVPlayer(playerItem: playerItem)

        let playerLayer = AVPlayerLayer(player: player)
        playerLayer.frame = view.bounds
        view.layer.addSublayer(playerLayer)
    }
}

Interactive Custom UI

With UNNotificationExtensionUserInteractionEnabled set to true, the content extension supports gesture recognizers, buttons, and other interactive elements.

class InteractiveNotificationViewController: UIViewController, UNNotificationContentExtension {
    private var ratingStars: [UIButton] = []
    private var selectedRating = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        setupRatingUI()
    }

    func didReceive(_ notification: UNNotification) {
        // Configure with notification content
    }

    private func setupRatingUI() {
        let stack = UIStackView()
        stack.axis = .horizontal
        stack.spacing = 8
        stack.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(stack)

        for i in 1...5 {
            let button = UIButton(type: .system)
            button.setImage(UIImage(systemName: "star"), for: .normal)
            button.tag = i
            button.addTarget(self, action: #selector(starTapped(_:)), for: .touchUpInside)
            stack.addArrangedSubview(button)
            ratingStars.append(button)
        }

        NSLayoutConstraint.activate([
            stack.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            stack.centerYAnchor.constraint(equalTo: view.centerYAnchor),
        ])
    }

    @objc private func starTapped(_ sender: UIButton) {
        selectedRating = sender.tag
        for (index, button) in ratingStars.enumerated() {
            let imageName = index < selectedRating ? "star.fill" : "star"
            button.setImage(UIImage(systemName: imageName), for: .normal)
        }
        // Send rating to server
        Task {
            await submitRating(selectedRating)
        }
    }
}

Communication Notifications

Communication notifications display the sender's avatar and name prominently. They use SiriKit intents (INSendMessageIntent or INStartCallIntent) to provide participant information and can have different Focus and summary behavior, so use them only for real person-to-person communication.

Setup

1. Enable the Communication Notifications capability on the app target.
2. Add supported intent class names, such as INSendMessageIntent, to NSUserActivityTypes in Info.plist.
3. Add the Intents framework to the Notification Service Extension target.
4. Configure an INSendMessageIntent, create an INInteraction, set direction = .incoming, donate the interaction, then call content.updating(from:) before passing the updated content to the content handler.

import Intents
import UserNotifications

extension NotificationService {
    func configureCommunicationNotification(
        content: UNMutableNotificationContent,
        senderName: String,
        senderImageURL: String?,
        conversationId: String
    ) async -> UNNotificationContent? {
        // Create the sender identity
        let handle = INPersonHandle(value: conversationId, type: .unknown)
        var avatar: INImage? = nil

        // Download sender avatar
        if let urlString = senderImageURL,
           let url = URL(string: urlString) {
            if let (data, _) = try? await URLSession.shared.data(from: url) {
                avatar = INImage(imageData: data)
            }
        }

        let nameComponents = PersonNameComponentsFormatter()
            .personNameComponents(from: senderName)

        let sender = INPerson(
            personHandle: handle,
            nameComponents: nameComponents,
            displayName: senderName,
            image: avatar,
            contactIdentifier: nil,
            customIdentifier: conversationId
        )

        // Create the messaging intent
        let intent = INSendMessageIntent(
            recipients: nil,
            outgoingMessageType: .outgoingMessageText,
            content: content.body,
            speakableGroupName: nil,
            conversationIdentifier: conversationId,
            serviceName: nil,
            sender: sender,
            attachments: nil
        )

        // Donate the interaction so Siri learns about this contact
        let interaction = INInteraction(intent: intent, response: nil)
        interaction.direction = .incoming
        try? await interaction.donate()

        do {
            return try content.updating(from: intent)
        } catch {
            print("Failed to update content with intent: \(error)")
            return nil
        }
    }
}

Handling in the Service Extension

The complete flow integrates communication notifications into the standard service extension:

override func didReceive(
    _ request: UNNotificationRequest,
    withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void
) {
    guard let content = request.content.mutableCopy() as? UNMutableNotificationContent else {
        contentHandler(request.content)
        return
    }

    Task {
        // Download and attach image
        if let imageUrl = content.userInfo["imageUrl"] as? String {
            await attachImage(from: imageUrl, to: content)
        }

        // Configure as communication notification if sender info is present
        if let senderName = content.userInfo["senderName"] as? String,
           let conversationId = content.userInfo["conversationId"] as? String {
            let senderImage = content.userInfo["senderImageUrl"] as? String

            let handle = INPersonHandle(value: conversationId, type: .unknown)
            var avatar: INImage? = nil
            if let urlString = senderImage,
               let url = URL(string: urlString),
               let (data, _) = try? await URLSession.shared.data(from: url) {
                avatar = INImage(imageData: data)
            }

            let nameComponents = PersonNameComponentsFormatter()
                .personNameComponents(from: senderName)

            let sender = INPerson(
                personHandle: handle,
                nameComponents: nameComponents,
                displayName: senderName,
                image: avatar,
                contactIdentifier: nil,
                customIdentifier: conversationId
            )

            let intent = INSendMessageIntent(
                recipients: nil,
                outgoingMessageType: .outgoingMessageText,
                content: content.body,
                speakableGroupName: nil,
                conversationIdentifier: conversationId,
                serviceName: nil,
                sender: sender,
                attachments: nil
            )

            let interaction = INInteraction(intent: intent, response: nil)
            interaction.direction = .incoming
            try? await interaction.donate()

            if let updatedContent = try? content.updating(from: intent) {
                contentHandler(updatedContent)
                return
            }
        }

        contentHandler(content)
    }
}

Extension Gotchas

Service extension not running:

• Verify mutable-content: 1 is set in the APNs payload.
• The notification must have an alert (title or body). Silent pushes do not trigger the service extension.
• Confirm the service extension target is embedded in the containing app and its bundle identifier/provisioning profile are valid.
• Confirm both targets include the same App Group or Keychain Sharing entitlements if they share data.

Content extension not showing:

• Verify the UNNotificationExtensionCategory in Info.plist matches the categoryIdentifier in the notification.
• Check that the storyboard or programmatic UI is properly configured.
• Ensure UNNotificationExtensionInitialContentSizeRatio is set to a reasonable value.

Memory pressure:

• Extensions are memory-constrained and can be terminated under pressure.
• Avoid loading large frameworks (no SwiftUI, no heavy networking libraries).
• Use URLSession directly for network requests in extensions.

Fallback handling:

• Always call the content handler exactly once on every path.
• On download, decryption, donation, or content.updating(from:) failure, return the original or best-attempt content rather than dropping the notification.
• In serviceExtensionTimeWillExpire(), stop waiting for in-flight work and call the content handler immediately with the best content available.

Network access in extensions:

• Extensions can make network requests. Use URLSession with the .default configuration.
• Keep requests fast -- the service extension has approximately 30 seconds total.
• Handle network failures gracefully; fall back to showing what the original payload contains.

Debugging extensions:

• In Xcode, select the extension scheme and attach to the extension process.
• Use Debug > Attach to Process by PID or Name with the extension's process name.
• Use os_log or print statements and view them in Console.app filtered by the extension's bundle identifier.
• Set breakpoints in the extension target and trigger a notification to hit them.

Complete Service Extension Example

A production-ready service extension that handles image download, body decryption, and communication notifications:

import UserNotifications
import Intents

class NotificationService: UNNotificationServiceExtension {
    private var contentHandler: ((UNNotificationContent) -> Void)?
    private var bestAttemptContent: UNMutableNotificationContent?

    override func didReceive(
        _ request: UNNotificationRequest,
        withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void
    ) {
        self.contentHandler = contentHandler
        bestAttemptContent = request.content.mutableCopy() as? UNMutableNotificationContent

        guard let content = bestAttemptContent else {
            contentHandler(request.content)
            return
        }

        Task {
            // Step 1: Decrypt body if needed
            if let encrypted = content.userInfo["encryptedBody"] as? String,
               let decrypted = decryptBody(encrypted) {
                content.body = decrypted
            }

            // Step 2: Download and attach image
            if let imageUrl = content.userInfo["imageUrl"] as? String {
                await attachMedia(from: imageUrl, to: content)
            }

            // Step 3: Configure communication notification
            if let senderName = content.userInfo["senderName"] as? String,
               let convId = content.userInfo["conversationId"] as? String {
                if let updated = await configureAsCommunication(
                    content: content,
                    senderName: senderName,
                    senderImageURL: content.userInfo["senderImage"] as? String,
                    conversationId: convId
                ) {
                    finish(with: updated)
                    return
                }
            }

            finish(with: content)
        }
    }

    override func serviceExtensionTimeWillExpire() {
        if let content = bestAttemptContent {
            finish(with: content)
        }
    }

    // MARK: - Private

    private func finish(with content: UNNotificationContent) {
        guard !didComplete, let handler = contentHandler else { return }
        didComplete = true
        handler(content)
    }

    private func decryptBody(_ base64: String) -> String? {
        guard let data = Data(base64Encoded: base64) else { return nil }
        guard let keyData = SharedKeychain.loadData(
            account: "notificationEncryptionKey"
        ) else { return nil }
        // Decrypt using CryptoKit or similar
        return try? Decryptor.decrypt(data, key: keyData)
    }

    private func attachMedia(
        from urlString: String,
        to content: UNMutableNotificationContent
    ) async {
        guard let url = URL(string: urlString) else { return }
        do {
            let (data, response) = try await URLSession.shared.data(from: url)
            let ext = fileExtension(for: response.mimeType)
            let fileURL = FileManager.default.temporaryDirectory
                .appendingPathComponent(UUID().uuidString + ext)
            try data.write(to: fileURL)
            let attachment = try UNNotificationAttachment(
                identifier: UUID().uuidString,
                url: fileURL,
                options: nil
            )
            content.attachments = [attachment]
        } catch {
            // Image download failed -- notification displays without media
        }
    }

    private func configureAsCommunication(
        content: UNMutableNotificationContent,
        senderName: String,
        senderImageURL: String?,
        conversationId: String
    ) async -> UNNotificationContent? {
        let handle = INPersonHandle(value: conversationId, type: .unknown)
        var avatar: INImage? = nil

        if let urlStr = senderImageURL,
           let url = URL(string: urlStr),
           let (data, _) = try? await URLSession.shared.data(from: url) {
            avatar = INImage(imageData: data)
        }

        let nameComponents = PersonNameComponentsFormatter()
            .personNameComponents(from: senderName)

        let sender = INPerson(
            personHandle: handle,
            nameComponents: nameComponents,
            displayName: senderName,
            image: avatar,
            contactIdentifier: nil,
            customIdentifier: conversationId
        )

        let intent = INSendMessageIntent(
            recipients: nil,
            outgoingMessageType: .outgoingMessageText,
            content: content.body,
            speakableGroupName: nil,
            conversationIdentifier: conversationId,
            serviceName: nil,
            sender: sender,
            attachments: nil
        )

        let interaction = INInteraction(intent: intent, response: nil)
        interaction.direction = .incoming
        try? await interaction.donate()

        return try? content.updating(from: intent)
    }

    private func fileExtension(for mimeType: String?) -> String {
        switch mimeType {
        case "image/jpeg": return ".jpg"
        case "image/png": return ".png"
        case "image/gif": return ".gif"
        case "video/mp4": return ".mp4"
        case "audio/mpeg": return ".mp3"
        default: return ".jpg"
        }
    }
}