What It Means & How to Fix It in UE5

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🧠 Why You’re Seeing This Error

This error means Unreal Engine found a .Build.cs file, but it couldn’t associate that module with any valid build target — like your game, editor, or plugin.

It usually happens when:

• A module exists in your project or plugin folder, but it’s not listed in any .Target.cs, .uproject, or .uplugin
• You added a new module but forgot to include it in ExtraModuleNames
• You created a plugin and added a module folder, but didn’t register it in the .uplugin file
• The module’s folder or file name doesn’t match what Unreal expects

In short: Unreal sees the module’s build file, but doesn’t know what to do with it.

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💥 Example Error Message

ERROR: Module rules file 'MyPlugin/Source/MyUnlinkedModule/MyUnlinkedModule.Build.cs' is not associated with any build target

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🛠️ What Usually Causes This

❌ The Module Exists, but Isn’t Listed in Any Build Target

MyGameEditor.Target.cs
ExtraModuleNames.Add("MyGame"); // ❌ Missing "MyUnlinkedModule"

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❌ It’s a Plugin Module That Isn’t Registered in .uplugin

// ❌ Missing module entry
"Modules": []

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❌ The Module Name Doesn’t Match the Folder or Build.cs File

Wrong: Source/MyPluginModule/PluginRules.cs
Right: Source/MyPluginModule/MyPluginModule.Build.cs ✅

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❌ The Module Folder Is in the Wrong Place

• Plugin modules must go under Plugins/YourPlugin/Source/ModuleName/
• Project modules must go under Source/ModuleName/

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✅ How to Fix It – Step-by-Step

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✔️ 1. If It’s a Project Module: Add It to ExtraModuleNames

In YourGameEditor.Target.cs (or YourGame.Target.cs), add:

ExtraModuleNames.Add("MyUnlinkedModule"); // ✅ Must match folder + Build.cs class

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✔️ 2. If It’s a Plugin Module: Register It in Your .uplugin

"Modules": [
  {
    "Name": "MyUnlinkedModule",
    "Type": "Runtime",
    "LoadingPhase": "Default"
  }
]

Make sure:

• The "Name" matches the folder and Build.cs file
• The "Type" fits the module (Runtime, Editor, Developer, etc.)

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✔️ 3. Match the Build.cs File and Folder Naming

✅ This is correct:

Source/MyModule/MyModule.Build.cs

❌ This will break:

Source/MyModule/WrongName.Build.cs

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✔️ 4. Regenerate Project Files

Once it’s hooked up correctly:

• Right-click your .uproject
• Select “Generate Visual Studio project files”
• Then reopen and rebuild

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✅ Summary: How to Fix “Module Rules File Is Not Associated With Any Build Target” in UE5

Cause	Fix
Module not listed in ExtraModuleNames	Add it to .Target.cs
Plugin module not in .uplugin	Register it under "Modules" with correct "Name" and "Type"
File/folder name mismatch	Ensure MyModule.Build.cs matches MyModule/ folder
Stale project setup	Regenerate project files after making changes