What Are Push Notifications in iOS?
Push notifications are server-initiated messages that allow apps to communicate with users even when the app isn't actively running. They're delivered through Apple Push Notification service (APNs), Apple's centralized service that handles message routing between app servers and iOS devices. Push notifications enable real-time updates, alerts, and content delivery without requiring users to manually check apps for new information.
What Are Live Activities?
Live Activities are real-time, glanceable widgets introduced in iOS 16 that display ongoing information directly on the Lock Screen and Dynamic Island. They provide users with up-to-date information about time-sensitive events without requiring app launches.
Core Characteristics
- Persistent Display: Remain visible on Lock Screen and Dynamic Island
- Real-Time Updates: Content refreshes automatically via push notifications
- Glanceable Information: Designed for quick consumption of essential data
- Interactive Elements: Support tap gestures to open the associated app
- Time-Bounded: Automatically expire after specific durations or manual dismissal
Common Use Cases
Sports & Entertainment
- Live Game Scores: Real-time score updates, quarter/period information
- Tournament Brackets: Match progression and upcoming games
- Concert Information: Stage times, artist lineups, venue updates
Transportation & Logistics
- Flight Tracking: Gate changes, departure delays, boarding status
- Delivery Updates: Package location, estimated arrival times
- Ride Sharing: Driver location, estimated pickup time
Food & Services
- Order Tracking: Restaurant preparation status, delivery progress
- Appointment Reminders: Queue position, estimated wait times
- Timer-Based Activities: Workout routines, cooking timers
Technical Architecture
ActivityKit Framework
Live Activities are powered by ActivityKit, Apple's framework for creating and managing ongoing activities:
import ActivityKit
// Define activity attributes (static data)
struct DeliveryAttributes: ActivityAttributes {
public struct ContentState: Codable, Hashable {
// Dynamic data that changes over time
var status: String
var estimatedDelivery: Date
var currentLocation: String
}
// Static data that doesn't change
var orderNumber: String
var customerName: String
}
Live Activity Lifecycle
- Creation: App requests new activity with initial state
- Updates: Content refreshes via push notifications or in-app updates
- Expiration: Automatic removal after 8 hours or manual dismissal
- Cleanup: System handles memory and display management
Display Locations
Lock Screen Integration
- Prominent Positioning: Appears above notifications
- Rich Content: Supports images, progress indicators, and formatted text
- Multiple Activities: Users can have several concurrent Live Activities
Dynamic Island (iPhone 14 Pro+)
- Compact View: Minimized state showing essential information
- Expanded View: Detailed information when tapped or long-pressed
- Adaptive Layout: Automatically adjusts based on content and screen space
The Problem with Traditional Live Activity Updates
Current Limitations
- Token Management Overhead: App servers must maintain individual push tokens for each active Live Activity
- Scalability Issues: For events with thousands of viewers (sports games, flight updates), servers send identical payloads to each token individually
- Infrastructure Strain: Mass events require substantial server resources and APNs quota consumption
- Delivery Inefficiency: Same content transmitted multiple times instead of once
Real-World Impact
Sports apps serving 50,000+ concurrent users face significant infrastructure costs and complexity when updating Live Activities for popular games.
Introducing Broadcast Push Notifications
Core Concept
Broadcast Push Notifications introduce a channel-based delivery system similar to traditional broadcasting:
- Single Push Request: One notification reaches all subscribers
- Channel Architecture: Events are associated with unique channel IDs
- Automatic Distribution: APNs handles delivery to all subscribed devices
- Resource Efficiency: Dramatically reduces server load and APNs quota usage
Key Benefits
- Simplified Architecture: No push token management required
- Instant Scalability: Effortlessly reach unlimited subscribers
- Cost Reduction: Single API call vs. thousands of individual requests
- Reliability: APNs ensures consistent delivery across all devices
Technical Implementation Guide
1. Enable Broadcast Capability
Developer Portal Configuration
- Navigate to App Capabilities
- Locate Push Notifications section
- Enable Broadcast Toggle - New iOS 18 feature
- Update provisioning profiles accordingly
2. Channel Creation Methods
Development/Testing: Push Notifications Console
1. Access Push Notifications Console
2. Navigate to Channels tab
3. Select 'New Channel'
4. Configure environment (Development/Production)
5. Choose message storage policy
6. Generate unique channel ID (base64 encoded)
Production: APNs Channel Management API
- Server-side channel creation via direct APNs integration
- Programmatic channel lifecycle management
- Authentication via existing APNs certificates/tokens
3. Message Storage Policies
No Storage Policy
- Use Case: High-frequency updates (live sports scores)
- Behavior: Delivery only to connected devices
- Advantage: Higher publishing budget allocation
- Trade-off: Offline devices miss updates
Most Recent Message Policy
- Use Case: Critical updates requiring guaranteed delivery
- Behavior: Stores latest message for offline devices
- Advantage: Ensures all subscribers receive updates
- Trade-off: Lower publishing budget
4. Live Activity Subscription Implementation
// Request a Live Activity and subscribe to broadcast push notifications
import ActivityKit
func startLiveActivity(channelId: String) {
let gameAttributes = GameAttributes()
let initialState = GameAttributes.ContentState(
home: 0,
away: 0,
update: "First Half"
)
do {
let activity = try Activity.request(
attributes: gameAttributes,
content: .init(state: initialState, staleDate: nil),
pushType: .channel(channelId) // Key change for broadcast
)
print("Live Activity started with channel: \(channelId)")
} catch {
// Handle activity request errors
print("Failed to start Live Activity: \(error)")
}
}
Critical Implementation Points
- Channel ID Retrieval: Fetch from server before activity creation
-
Push Type Parameter: Use
.channel(channelId)instead of traditional token-based approach - Error Handling: Implement robust error handling for network and ActivityKit failures
5. Broadcast Push Notification Structure
Payload Format
{
"aps": {
"alert": {
"title": "Game Update",
"body": "Home team scores!"
},
"priority": "high"
},
"home_score": 2,
"away_score": 1,
"update_text": "Goal in 23rd minute",
"timestamp": 1234567890
}
Delivery Configuration
- Priority Levels: High for immediate delivery, normal for standard updates
- Content Structure: Match your Live Activity's ContentState model
- Timestamp Inclusion: Essential for proper update ordering
Production Deployment Strategy
Server Integration Requirements
Channel Management API Integration
- Create Channels: Programmatic channel creation for new events
- Delete Channels: Remove unused channels to stay within limits
- Monitor Usage: Track active channel count and subscription metrics
Broadcast Push API Integration
- Authentication: Reuse existing APNs certificate/token authentication
- Rate Limiting: Respect APNs guidelines for broadcast frequency
- Error Handling: Implement retry logic for failed broadcasts
Architecture Recommendations
Event-Channel Mapping
// Example channel ID strategy
let channelId = "game_\(homeTeam)_vs_\(awayTeam)_\(date)"
let flightChannelId = "flight_\(airline)_\(flightNumber)_\(date)"
Lifecycle Management
- Creation Timing: Generate channels when events are scheduled
- Cleanup Strategy: Delete channels post-event completion
- Monitoring: Track subscriber counts and engagement metrics
Best Practices and Considerations
Channel Lifecycle Management
- Creation Strategy: Generate channels when events are scheduled, not when first user subscribes
- Cleanup Protocol: Delete channels immediately after event completion to stay within 10,000 channel limit
- Monitoring Requirements: Track active subscriber counts and channel usage patterns
- Expiration Handling: Implement automatic cleanup for abandoned or expired channels
Channel Limits and Quotas
- Maximum Channels: 10,000 active channels per app (Development and Production environments)
- Publishing Budget: Higher budget available with "No Storage" policy
- Rate Limiting: Follow APNs guidelines for broadcast frequency
- Geographic Distribution: APNs handles global delivery automatically
Performance Optimization
Network Efficiency
- Payload Size: Keep broadcast payloads minimal for faster delivery
- Priority Management: Use high priority sparingly for critical updates only
- Batch Operations: Group related updates when possible
- Error Handling: Implement robust retry mechanisms for failed broadcasts
User Experience Considerations
- Update Frequency: Balance real-time updates with battery conservation
- Content Relevance: Ensure broadcasts provide meaningful value to all subscribers
- Graceful Degradation: Handle offline scenarios appropriately
- Performance Monitoring: Track delivery success rates and user engagement
Testing and Debugging
Development Workflow
- Push Notifications Console: Essential for initial testing and validation
- Channel Management: Test creation, subscription, and deletion flows
- Payload Validation: Verify JSON structure matches ContentState model
- Error Simulation: Test failure scenarios and recovery mechanisms
Production Monitoring
- Delivery Metrics: Track successful broadcast delivery rates
- Subscriber Analytics: Monitor channel subscription patterns
- Performance Alerts: Set up monitoring for failed broadcasts
- User Feedback: Implement mechanisms to detect and resolve issues
Security and Privacy
Data Protection
- Payload Encryption: APNs provides end-to-end encryption for all broadcasts
- Channel Access: Only apps with proper certificates can create/manage channels
- User Consent: Respect notification permissions and subscription preferences
- Data Minimization: Include only necessary information in broadcast payloads
Authentication Requirements
- APNs Authentication: Use existing certificate or token-based authentication
- Channel Verification: Validate channel ownership before broadcasting
- Server Security: Secure channel creation and management endpoints
- Access Control: Implement proper authorization for broadcast operations
Implementation Roadmap
Phase 1: Foundation Setup
- Enable broadcast capability in Developer Portal
- Create test channels using Push Notifications Console
- Implement basic subscription logic in app
- Test end-to-end flow with sample broadcasts
Phase 2: Production Integration
- Integrate Channel Management API in server infrastructure
- Implement production broadcast logic
- Add monitoring and alerting systems
- Deploy with gradual rollout strategy
Phase 3: Optimization
- Analyze performance metrics and user engagement
- Optimize payload structure and delivery frequency
- Implement advanced features like conditional broadcasting
- Scale infrastructure based on usage patterns
Summary
Broadcast Push Notifications for Live Activities in iOS 18 provide developers with powerful tools to create engaging, scalable real-time experiences. By following these implementation guidelines and best practices, teams can successfully leverage this technology to deliver exceptional user experiences while maintaining optimal performance and reliability.
Top comments (4)
Live Activities are real-time, glanceable widgets introduced in iOS 16 that display ongoing information directly on the Lock Screen and Dynamic Island. They provide users with up-to-date information about time-sensitive events without requiring app launches.
Broadcast push seems like a total game-changer...
This is the best solution to push notifications.
Interesting. Thanks for sharing!