What It Means & How to Fix It in UE5

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🧠 Why You’re Seeing This Error

This error means Unreal’s build system couldn’t process your build request because the build configuration is invalid or unsupported.

It usually happens when:

• You try to build with a nonexistent configuration (like UltraDebugShipping)
• You have a typo in the configuration name (e.g., Debbug instead of Debug)
• A configuration is missing platform support
• You’re using a custom Target.cs or Build.cs that doesn’t handle certain configurations properly

In short: UnrealBuildTool doesn’t know what to do with the configuration you gave it.

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💥 Example Error Message

UnrealBuildTool Exception: Invalid build configuration: UltraDebug

Or:

ERROR: Invalid build configuration 'TestFlightRelease' for target 'MyGame'

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🛠️ What Usually Causes This

❌ You’re Trying to Build a Non-Standard Configuration

RunUAT BuildCookRun -configuration=SuperDebug // ❌ Not a real configuration

UE5 supports:
Debug, DebugGame, Development, Shipping, Test

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❌ You Made a Typo in the Configuration Name

-configuration=Dvelopmet // ❌ Misspelled "Development"

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❌ Your .Target.cs Doesn’t Support the Config You’re Using

If your custom target logic restricts configurations, the build might fail.

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❌ CI or Command-Line Scripts Are Passing the Wrong Flags

This is common in Jenkins, GitHub Actions, or BuildGraph setups where config names are auto-passed in.

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✅ How to Fix It – Step-by-Step

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✔️ 1. Stick to Supported Configurations

Use one of the official Unreal build configs:

• Debug
• DebugGame
• Development ✅ (most common)
• Shipping
• Test

Example:

RunUAT BuildCookRun -project="MyGame.uproject" -configuration=Development

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✔️ 2. Double-Check for Typos or Wrong Case

-development → ❌ won’t work (should be -configuration=Development)
-debuggame → ❌ invalid casing (should be DebugGame)

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✔️ 3. If Using Custom Targets, Add Fallback Logic

If you’re using a custom Target.cs, you can add logging to ensure it handles various configurations:

Log.TraceInformation($"Building with config: {Target.Configuration}");

if (!Enum.IsDefined(typeof(UnrealTargetConfiguration), Target.Configuration))
{
    throw new BuildException($"Unsupported configuration: {Target.Configuration}");
}

Or simplify with a switch or default block.

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✔️ 4. If You Need a Custom Config, Register It Properly (Advanced)

You can define new configs in DefaultEngine.ini and customize behavior, but Unreal tooling may not fully support it unless you extend the build system.

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✅ Summary: How to Fix “UnrealBuildTool Exception: Invalid Build Configuration” in UE5

Cause	Fix
Unsupported build configuration	Use one of Unreal’s official configurations (Debug, Shipping, etc.)
Typo in configuration flag	Check for misspellings or case issues
Custom target doesn’t support config	Add fallback logic or conditionals in .Target.cs
CI/build script misconfiguration	Correct the configuration string being passed to the build tool