iPhone emulators are programs that replicate the hardware of an iPhone, allowing you to run iOS apps on other operating systems. App developers often use emulators to test iPhone software on the Windows or Mac computers they use for programming. While they can't run apps directly from the Apple App Store, these iPhone emulators faithfully mimic the basic functionality of an iPhone.

Xcode is the best emulator for iOS developers because Apple made it. It emulates all Apple devices, so you can see how your app’s layout changes on different iPhone models and iPad versions with and without Retina Display. This way, you can make sure your iOS 13 app is backwards compatible with iOS 10 devices.

Xcode also lets you modify the settings available on the simulated device, depending on the device and iOS version, to see how those settings affect your app. For example, you can test how your app behaves when the screen is rotated to ensure it works in both portrait and landscape modes. If you want to dig deeper into using Xcode to test your app, check out Apple's Xcode Help guide.

Smartface is designed for developing iOS apps on PCs and enables seamless cross-platform programming. You’ll need iTunes for Windows and the Smartface app for iOS. Once you’re set up, you can connect your iOS device to your computer.