Simforge: Run decrypted iOS Apps on iOS Simulator (Xcode)

Simforge is a tool designed to run decrypted apps in iOS Simulator, allowing you to easily create and test tweaks for all kinds of apps. This open-source application modifies the Mach-O binary headers to indicate simulator compatibility for iOS arm64 mach-o binaries. Use it to run (decrypted) iOS Apps on iOS Simulators.

What is Simforge?

SimForge is a powerful utility that bridges the gap between ARM64 iOS apps and Apple Silicon simulators. By intelligently modifying Mach-O binary headers, it tricks the simulator into recognizing iOS apps and dynamic libraries (dylibs) as "simulator-compatible"—even if it means bypassing their original code signatures.

This clever workaround allows developers to seamlessly run and test iOS apps (or inject custom dylibs) directly within the simulator environment, eliminating the need for a physical iPhone.

For tweak developers, this is a game-changer. Instead of repeatedly deploying tweaks to a real device, SimForge streamlines the process by letting you experiment and iterate right on the simulator. Whether you’re crafting UI customizations, app mods, or system tweaks, this tool cuts down tedious setup steps.

Simforge simplifies iOS tweak development with three core commands tailored for simulator workflows. The convert command modifies ARM64 iOS apps or dynamic libraries (dylibs) to run on Apple Silicon simulators by adjusting their Mach-O headers — though this process invalidates their original code signatures.

Once converted, the launch command takes over, letting you start the app directly in the simulator while injecting a custom dylib using the app’s bundle identifier. For projects requiring file modifications, makerw creates a read-write overlay of a directory, enabling edits to otherwise restricted files.

Together, these commands eliminate the need for physical devices: convert your app, inject tweaks on-the-fly, and test changes instantly (like with simject) — all within the Xcode simulator environment.

How to install and use Simforge on macOS

Getting started with simforge is simpler than you might think — though there are a few quick preparations to tackle first. Begin by installing Xcode from the Mac App Store, which gives you access to the iOS simulator and core development tools. Next, set up Theos, the go-to framework for building iOS tweaks, to ensure your environment is tweak-ready. Finally, open download the simforge app onto your Mac.

Don’t worry if this sounds unfamiliar! The simforge documentation walks you through every step, from installation hiccups to advanced configurations, so you can move from setup to simulator testing without missing a beat.

Here’s what you’ll need to do to get simforge running on your Mac:

Prerequisites:

• Xcode installed (with Command Line Tools).
• Theos configured on your system (for tweak development).
• An iOS simulator set up via Xcode.

Step 1. Install simforge on your Mac

• Download simforge from the official GitHub Repository releases page.

Step 2. Decrypt iOS App

• Download a decrypted app from our IPA Library or do it yourself following our How to decrypt IPA guide.

Step 3. Extract the IPA using unzip

• Extract the .app bundle from the IPA with unzip command or simply change the file name from .IPA file to .ZIP.

unzip /path/to/your-app-decrypted.ipa -d /path/to/destination/

Step 4. Convert App for Simulator

• Use simforge in the terminal app and convert the .app for usage with the iOS Simulator.

simforge convert /path/to/Payload/YourApp.app

Step 5. Code Sign the Modified App

• After conversion, the app needs to be re-signed. You can simply ad-hoc sign.

# Sign frameworks first
codesign -f -s - /path/to/Payload/YourApp.app/Frameworks/*

# Then sign the main app bundle
codesign -f -s - /path/to/Payload/YourApp.app

Step 6. Install the iOS App to Simulator

• Drag-and-drop YourApp.app folder into your simulator to install, or install via command line.

# List available simulators
xcrun simctl list devices

# Install the app (replace UUID with your simulator's identifier)
xcrun simctl install "SIMULATOR_UUID" /path/to/Payload/YourApp.app

Step 7. Launch with Dylib Injection (Optional)

• You can also launch an installed app with dylib injection.

simforge launch --bundleid com.example.app --dylib /path/to/tweak.dylib

FAQ

Written by

Kuba Pawlak

Kuba has over 20 years of experience in journalism, focusing on jailbreak since 2012. He has interviewed professionals from various companies. Besides journalism, Kuba specializes in video editing and drone flying. He studied IT at university before his writing career.

Post a comment