Extensions & Widgets API Reference

Comprehensive API reference for Apple's widget and extension ecosystem. Covers WidgetKit, ActivityKit, Control Center widgets, and App Groups data sharing.

When to Use This Reference

Use this reference when you need:

• Complete API signatures for WidgetKit or ActivityKit
• Timeline configuration options and refresh policies
• Live Activity data limits and update patterns
• Control Center widget implementation details
• App Groups entitlement and data sharing specifics
• watchOS or visionOS widget platform differences

For discipline patterns: See extensions-widgets for anti-patterns, troubleshooting, and decision trees.

Example Prompts

Questions you can ask Claude that will draw from this reference:

• "What are all the TimelineReloadPolicy options and when should I use each?"
• "What's the exact 4KB data limit for Live Activities and what counts toward it?"
• "How do I configure a Control Center widget with async ValueProvider?"
• "What are the differences between widget families on different platforms?"
• "How do I set up App Groups correctly for both targets?"
• "What's the complete ActivityAttributes implementation pattern?"

What's Covered

Standard Widgets (iOS 14+)

• Widget protocol and WidgetConfiguration
• TimelineProvider: getTimeline, getSnapshot, placeholder
• TimelineReloadPolicy: atEnd, after, never
• Widget families: systemSmall/Medium/Large, accessory variants
• WidgetCenter for reloads and configuration

Interactive Widgets (iOS 17+)

• Button and Toggle in widget views
• App Intent integration with perform()
• Configuration intents
• WidgetCenter.shared.reloadAllTimelines()

Live Activities (iOS 16.1+)

• ActivityAttributes definition
• Dynamic Island layouts (compact, minimal, expanded)
• 4KB content state limit
• Push notification updates
• ActivityKit request and update APIs

Control Center Controls (iOS 18+)

• Control protocol
• ValueProvider for async state
• ControlWidgetButton and ControlWidgetToggle
• Optimistic UI patterns

App Groups & Data Sharing

• Entitlement configuration
• UserDefaults(suiteName:) patterns
• Container URLs for file sharing
• Background refresh coordination

Platform Variations

• watchOS widget considerations
• visionOS widget support
• macOS desktop widgets

Troubleshooting

• Common failure patterns
• Debug logging techniques
• Memory limit issues

Expert Review Checklist

• 50+ item checklist for widget code review
• Timeline efficiency validation
• Data sharing verification

Key Pattern

Complete Widget Implementation

// Widget Configuration
@main
struct MyWidget: Widget {
    let kind = "MyWidget"

    var body: some WidgetConfiguration {
        StaticConfiguration(kind: kind, provider: Provider()) { entry in
            MyWidgetView(entry: entry)
        }
        .configurationDisplayName("My Widget")
        .description("Shows app data.")
        .supportedFamilies([.systemSmall, .systemMedium])
    }
}

// Timeline Provider
struct Provider: TimelineProvider {
    func placeholder(in context: Context) -> SimpleEntry {
        SimpleEntry(date: Date(), data: "Placeholder")
    }

    func getSnapshot(in context: Context, completion: @escaping (SimpleEntry) -> Void) {
        completion(SimpleEntry(date: Date(), data: fetchFromCache()))
    }

    func getTimeline(in context: Context, completion: @escaping (Timeline<SimpleEntry>) -> Void) {
        let data = fetchFromSharedDefaults()
        let entry = SimpleEntry(date: Date(), data: data)
        let timeline = Timeline(entries: [entry], policy: .after(Date().addingTimeInterval(3600)))
        completion(timeline)
    }
}

Documentation Scope

This page documents the axiom-extensions-widgets-ref reference skill—comprehensive API coverage Claude uses when you need specific API details for widgets and extensions.

For patterns and troubleshooting: See extensions-widgets for discipline patterns, anti-patterns, and debugging workflows.

Related

• extensions-widgets — Discipline skill with patterns and troubleshooting
• app-intents-ref — App Intents for interactive widgets
• swift-concurrency — Async patterns for data loading

Resources

WWDC: 2025-278, 2024-10157, 2024-10068, 2023-10028, 2023-10194, 2020-10028

Docs: /widgetkit, /activitykit, /widgetkit/making-a-configurable-widget