What It Means & How to Fix It in UE5

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🧠 Why You’re Seeing This Error

This error means the Unreal Engine build system (via Visual Studio or UnrealBuildTool) tried to include a header file like 'MyModule.h', but couldn’t find it in the include path.

It typically happens when:

• A module isn’t properly listed as a dependency in your .Build.cs file
• You’re using the wrong include path or the file doesn’t exist
• The module isn’t compiled or hasn’t been added to the build target

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💥 Example Error Message

fatal error C1083: Cannot open include file: 'MyModule.h': No such file or directory

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🛠️ What Usually Causes This

❌ The Header File Exists, But the Module Isn’t Listed as a Dependency

// In MyActor.cpp
#include "MyModule.h" // ❌ But the module isn’t in your .Build.cs dependencies

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❌ The Header File Path Is Wrong or Doesn’t Exist

#include "SomeFolder/MyModule.h" // ❌ Incorrect path

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❌ The Header Belongs to Another Plugin or Private Folder

If you’re including a header from a plugin or from a module’s Private folder, access might be restricted.

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✅ How to Fix It – Step-by-Step

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✔️ 1. Add the Module as a Dependency in Your .Build.cs File

Let’s say you’re trying to include a file from MyAwesomeModule. Open your module’s .Build.cs and add:

PublicDependencyModuleNames.AddRange(new string[]
{
    "Core",
    "CoreUObject",
    "Engine",
    "MyAwesomeModule" // ✅ Add the missing module here
});

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✔️ 2. Use the Correct Include Path

If the header lives in MyAwesomeModule/Classes/Utilities/MyUtil.h, include it like this:

#include "Utilities/MyUtil.h" // ✅ Don't include the "Classes" folder

You typically don’t include the module name in the path — just the folder structure after Public/.

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✔️ 3. Only Include Headers From Public Folders

Unreal modules expose headers via the Public/ folder. If you’re trying to include from a Private/ folder of another module, you’ll get this error.

✅ Allowed:

MyModule/Public/MyHeader.h

❌ Not allowed (from outside the module):

MyModule/Private/MyInternalHeader.h

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✔️ 4. Rebuild and Regenerate Project Files

After fixing includes and dependencies:

• Delete Intermediate/ and Binaries/ folders (optional)
• Right-click your .uproject → Generate Visual Studio project files
• Recompile the project

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✅ Summary: How to Fix “Cannot Open Include File: ‘ModuleName.h’” in UE5

Cause	Fix
Missing module dependency	Add the module to PublicDependencyModuleNames in .Build.cs
Incorrect include path	Match the folder structure under the module’s Public/ folder
File is in a private folder	Move the file to Public/ if you need it in another module
Wrong or non-existent file name	Double-check spelling, casing, and path