unixzii / SimRun

# SimRun
SimRun runs iPhone apps on your Mac, each in its own ordinary Mac window.
It takes the app you already build for the iOS Simulator in Xcode, unchanged, and starts it directly. There is no simulated iPhone to boot, no home screen, no device frame: just your app, in a
window, controlled with your mouse, trackpad and keyboard.
> SimRun is an experimental research project. It's useful for day-to-day work on an app's UI, but it is not a
> replacement for testing in the Simulator or on a real device.
## Why not just use the Simulator, or Mac Catalyst?
**Compared with the iOS Simulator**
- **Nothing to boot.** The Simulator starts a whole virtual iPhone before your app can run. SimRun starts only your
 app, so it's on screen in about half a second.
- **Lighter.** None of the simulated phone's background system runs. Only your app and a few small helpers do.
- **Apps are real windows.** Every app gets its own Mac window. Put several apps side by side, resize them, or
 minimize them like any other window.
- **Your trackpad works naturally.** Two-finger scrolling, pinch to zoom and rotate gestures turn into real
 multi-touch input. No Option-dragging to fake a second finger.
- **Fits into the terminal.** Launch an app from the command line and its output prints right there. When the app
 exits, the command exits with the same status, which is handy in scripts.
- **Easy to look inside.** One click opens an app's data folder in Finder or wipes it, and a Keychain window shows
 everything apps have saved there, passwords included.
**Compared with Mac Catalyst**
- **No porting.** Catalyst means making a Mac version of your app: a new build target, Mac-specific code paths, and
 APIs that behave differently. SimRun runs the iOS Simulator build you already have.
- **Looks and behaves like the iPhone version.** Your app runs with the iPhone's own UIKit and SwiftUI, so layouts,
 controls and Liquid Glass look the way they do on a phone, not the way they're adapted for the Mac.
- **Works with apps you didn't write.** Any iOS Simulator build can be opened, including ones you received from
 someone else, without access to the source. So can most builds for devices (see Tips).
## What you need
- A Mac with Apple silicon
- Xcode, with an iOS Simulator runtime installed (SimRun uses the newest one it finds; pick another in SimRun ▸ iOS
 Runtime, or for one app with Launch With…). For Apple Watch apps, a watchOS Simulator runtime too
- System Integrity Protection (SIP) turned off. SimRun needs to load its own code into iOS apps, which macOS only
 allows with SIP off. Apple describes how to change this setting in
 Disabling and Enabling System Integrity Protection.
SimRun is developed on macOS 27.2 with Xcode 27.1 and the iOS 27.1 runtime; the iOS 27.0, 26.5 and 18.6 runtimes work too.
Other versions may or may not work.
## Install
### Download a release
Each release has a `SimRun- .zip` with a ready-built
`SimRun.app`. Download it, unzip it, and move `SimRun.app`