Unreal Engine Packaging Failed (Unknown Cook Failure)

How to fix it

Try these in order — the most common fix is first.

1. 1. Find the first error

   Copy steps
   1. Open Output Log > Show full log, or the UAT log in Saved/Logs
   2. Scroll up from ExitCode=25 and find the first 'Error:' or failed ensure
   Did this fix it? Yes No

2. 2. Fix references

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   1. Right-click Content folders > Fix Up Redirectors in Folder
   2. Resolve 'Failed to load' and 'Can't find file' warnings
   Did this fix it? Yes No

3. 3. Clean build artifacts

   1. Delete Saved/Cooked, Intermediate and DerivedDataCache entries for the project and package again
   Did this fix it? Yes No

4. 4. Check SDKs and memory

   Copy steps
   1. Confirm Visual Studio workloads and platform SDKs match your engine version
   2. Reduce very large textures and close other apps while cooking
   Did this fix it? Yes No

Symptoms

Package Project ends with 'Packaging failed', 'UATHelper: Packaging ... ExitCode=25 (Error_UnknownCookFailure)' or a cook crash.

Why it happens

• Broken or missing asset references
• Assets marked never-cook or engine content referenced
• Redirectors left from moved assets
• Out of memory on huge textures
• Toolchain or SDK mismatch

This guide also covers

• unreal engine packaging failed
• unknown cook failure unreal
• unreal engine packaging error exitcode 25

Other Unreal Engine errors

• Unreal Engine Fatal Error Crash
• Unreal Engine GPU Crashed or D3D Device Removed
• Unreal Engine Shaders Compiling Forever (Stuck at 45%)
• Unreal Engine Out of Video Memory Error
• Unreal Engine Project Won't Open After Upgrade
• Epic Games Launcher Stuck Installing Unreal Engine
• Unreal Engine Visual Studio C++ Build Errors
• Unreal Engine 5 Lumen and Nanite Low FPS