iOS

iOS apps are written in Swift (or the older Objective-C) with SwiftUI or UIKit, built in Xcode, and run in a sandbox with strict rules on background work, permissions and privacy, such as asking before tracking users across other companies' apps. Apple makes both the hardware and the software, so there are far fewer device models and system versions to test than on Android, and most users update quickly.

Building an iOS app needs a Mac with Xcode (or a cloud build service), and publishing needs the Apple Developer Program at $99 a year. Apps reach users through the App Store after App Review; in the EU and Japan, local laws also allow alternative app marketplaces. Push notifications go through APNs (Apple Push Notification service).