Modification of mobile games has become incredibly popular a hobby that for many has grown into a serious passion for programming and reverse engineering. Users strive not just to play, but to change the gameplay to suit themselves: add unlimited resources, disable advertising or open closed content. However, the process of creating modifications requires a deep understanding of the application file structure and working with tools. Creating mods is not just hacking, but complex technical work with resources. You will have to deal with
Creating mods is not just hacking, but complex technical work with binary code and resources. You will have to deal with formats .apk and .dexformats, understand the structure of the project and learn to use specialized software. In this guide, we will analyze all the stages from preparing the environment to the final assembly of the modified application.
Before you begin, it is important to realize that any manipulations with the code of other software can lead to unstable operation of the application. Android system strictly monitors the integrity of signatures, so any modified file will require a new signature for installations. Ready to dive into the world of modding? Then let's start by choosing the right tools.
⚠️ Attention: Modifying games may violate the developer's user agreement. Use the acquired knowledge only for educational purposes or to create mods for your own projects.
Selecting and setting up modding tools
The first step is to install the necessary software. For working directly on a smartphone, the most popular solutions are MT Manager and APK Editor Pro. These applications are powerful machines that allow you to view, edit and compile files without the need for a personal computer.
If you plan to do serious reverse engineering, you can't do without a PC. The standard set of a professional includes APKTool for decompiling resources, Jadx for viewing Java code and Android Studio for debugging. A combination of these apps allows you to conduct an in-depth analysis of the game logic.
For beginners who want to try their hand directly from their phone, installation MT Manager will be the optimal solution. The app interface is divided into two panels, which is convenient for comparing original and modified files. It is important to grant the application all the necessary permissions to access the file system.
- 🛠️ MT Manager —the best choice for editing APK directly on the device.
- 💻 APKTool + Jadx —a professional suite for deep code analysis on a PC.
- 📝 Hex Editor —useful for editing binary data and searching for specific values.
- 🔐 Uber Apk Signer —essential for quick re-signing collected packages.
⚠️ Attention: Download modding tools only from official websites or trusted forums (for example, 4PDA or XDA). Versions from random sources may contain malicious code.
APK structure file and decompilation
Any Android application is packaged in an archive .apk, which is essentially a renamed ZIP archive. It stores compiled code (files classes.dex), resources (images, sounds, XML layouts) and application manifest AndroidManifest.xml. Understanding this structure is critical to successful modding.
The decompilation process turns compiled code into a readable format. When using MT Manager just click on the APK file and select “View”. For deeper work, select the “Decompilation” option, which creates a folder with decrypted resources and code in the format Smali.
Smali is an assembly-like language into which Java code for the Dalvik/ART virtual machine is compiled. This is where the main magic of changing the logic of the game happens. You won't see the usual Java classes, but you can find methods that change variable values or check conditions.
| APK component | Description | What can be changed |
|---|---|---|
AndroidManifest.xml |
Application passport | Permissions, package name, period input |
classes.dex |
Compiled code | Game logic, prices, victory conditions |
resources.arsc |
Resource table | Texts, level names, descriptions |
res/ |
Resources folder | Icons, interface graphics, sounds |
After making changes, the files must be compiled back. This process is called assembly. Errors during the build phase often indicate syntax errors in the Smali code or corrupted resources.
Why is the code called Smali?
Smali is the human representation of Dalvik bytecode. It was created to allow developers to read and edit code that would otherwise be incomprehensible without a disassembler. This is not a full-fledged programming language, but rather an intermediate representation.
Resource editing and localization
The simplest type of modification is changing resources. This includes replacing icons, changing menu texts, translating the game into another language, or editing numeric values in configuration files. Often such data is stored in files strings.xml or arrays.xml inside a folder res/values.
To change the text, just open the corresponding XML file in the editor, find the desired line by key and replace the contents of the tag. For example, to change the name of the game in the menu, you need to find the line app_name and enter a new value. XML structure must remain valid, otherwise the application will crash upon launch.
More complex resources, such as images, are replaced by importing new files into folder res/drawable. It is important to follow the naming convention: use only Latin letters, numbers and underscores. Spaces and capital letters in file names are not allowed.
- 🎨 Replace graphics in the folder
res/drawableorres/mipmap. - 📝 Texts change in files
strings.xmlinsideres/values. - ⚙️ Numeric constants are often stored in
integers.xmlordimens.xml.
⚠️ Attention: When replacing images, make sure that the format and resolution of the new file matches the original. A discrepancy can lead to interface distortion or application crash.
Before replacing any resources, be sure to make a backup copy of the original res folder. This will allow you to quickly roll back changes if the new graphics break the interface layout.
Changing the game logic through Smali code
Real modding begins where editing resources ends. To make the game free, remove ads or give endless health, you need to get into the code classes.dex. After decompilation, you will receive many files .smalithat need to be analyzed.
Finding the right place in the code is often carried out using the “line search” method. If you want to remove purchase verification, look in the resources for the error text “Purchase failed” or “Not enough money”. When you move on to using this line in Smali code, you will find a method responsible for checking.
In the Smali language, instructions are executed sequentially. To bypass the check, it is often enough to change the transition condition. For example, the instruction if-eqz (go if equal to zero) can be replaced by if-nez (go if not equal to zero) or simply deleted. You can also replace the value returned by the method with const/4 v0, 0x1 (true).
An example of changing a condition in Smali
It was: if the money is less than the price, go to the error label
if-lt v1, v2, :cond_error
It became: we always skip the check (commented out or deleted line)
if-lt v1, v2, :cond_error
Working with code requires extreme care. One extra or missing line can break the call stack, causing the application to close immediately. Always check the register balance and structure of code blocks .method and .end method.
The main difficulty of modding logic is finding the right method among thousands of lines of code. Use a search using unique strings from the game interface to narrow down your search.
Working with libraries and Native code
Many modern games use engines like Unity or Unreal Engine, where the main logic is transferred to native libraries .so (Shared Object). These files are written in C++ and are located in the folder lib/. Modifying them is much more difficult, since knowledge of the processor assembler (ARM or ARM64) is required.
To edit native libraries, tools such as IDA Pro or Ghidraare used. They allow you to disassemble a binary file and find functions responsible for health, ammo or currency. Changes are made directly to the hexadecimal code (Hex) or using patches.
If you are a beginner, it is better to avoid mods that require editing libil2cpp.so or similar files. An error in a binary file is fatal and cannot be corrected through a simple recompilation. In such cases, they often look for ready-made patches on the Internet or use frameworks like LSPatch to implement code without changing the original.
⚠️ Attention: Editing native libraries (.so) requires advanced knowledge of processor architecture. Inexperienced intervention is guaranteed to lead to the application not working.
☑️ Preparing to edit the code
Assembling, signing and installing the mod
After making all the desired changes, the assembly stage begins. In MT Manager this is done by clicking the “Back” button and confirming the file update. The app will automatically compile the resources and code into a new APK file. However, this file cannot be installed yet.
Android requires that all applications be signed with a digital certificate. The original is signed with a developer key that you do not have access to. Therefore, the modified APK must be signed with your key (usually a test key). In file managers, this option is called “Sign APK.”
After successful signing, you can proceed with installation. Sometimes the system blocks installation due to a signature conflict with the already installed original version of the game. In this case, you must first delete the original application, saving the data (if possible), or change Package Name in the manifest so that the system perceives the mod as a completely new application.
- 📦 Compile the modified files into an APK.
- 🔑 Be sure to sign the compiled file as a test one key.
- 🗑️ Uninstall the original game before installing the mod (if the package names are the same).
- 🚀 Install the mod and check its functionality.
If the game crashes immediately after launch, check the logs using adb logcat or the built-in debugging tools. Errors often indicate a specific class or method where an editing error was made.
What is a signature conflict?
Android does not allow updating an application if the new version is signed with a different key than the installed one. This is protection against application substitution by attackers. Therefore, a mod signed with your key will not sit on top of the original from the developer.
Frequent errors and ways to solve them
During the modding process, you will inevitably encounter problems. The most common error is “App not installed”. This almost always means a signature problem or a mismatch in the processor architecture (for example, trying to run an ARM64 mod on an old 32-bit device).
Another common problem is an infinite crash on startup. This is a signal that you have violated the logic of the code. You may have removed an important method or changed the return type. In such cases, it helps to compare the modified Smali file with the original to find discrepancies.
It is also worth remembering about anti-cheat. Online games often have server-side background checks. If you change the amount of gold in the local file, the server will see this and block the account. Modding is safe mainly in offline projects.
Is it possible to make mods for online games without a ban?
In most cases, no. Data in online games is stored on the developer's server. Locally changing values (via a mod) will not affect the server, and an attempt to send fake data packets will be quickly detected by the anti-cheat system, which will lead to permanent blocking.
Do you need Root access to create mods?
No, root access is not required to create and install mods. It is enough to be able to install applications from unknown sources. Root may only be needed for the operation of some specific modules (for example, Lucky Patcher in emulation mode), but not for the APK build itself.
Why does the game require an update after installing the mod?
Developers release updates that change the code structure or file checksums. The mod made for the old version stops working. You need to download a new version of the original and apply the mods again, adapting them to the changed code.
Is it safe to download ready-made mods from the Internet?
There is always a risk. A finished mod from an unknown author may contain Trojans or miners. It's safer to learn how to create mods yourself or download them only from reputable forums where the community verifies the files.
What to do if MT Manager gives an error when compiling?
A compilation error usually indicates a syntax error in the Smali code or a corrupted resource. Read the error log carefully - it indicates the line number. Often the problem is solved by restoring one deleted bracket or register.