u4.exe is the executable file for Unreal Engine 4 (UE4), a popular game engine developed by Epic Games. It's used to run and test UE4 projects.
Prevention
If your error is related to a business utility or a specific driver package named "U4," the file may have been corrupted during a Windows Update or an improper shutdown. Uninstall the program associated with the error. Restart your computer to clear out cached file paths. u4.exe does not exist