Microsoft reveals why Windows 11 keeps saying a file is in use after closing app

Microsoft's Azure CTO Mark Russinovich explained why Windows displays "file in use" errors even after closing applications, identifying three main causes: antivirus software scanning files in the background, remote processes holding file references on a network, and DLL files loaded into memory that don't appear as standard file handles. To diagnose and resolve these issues, users can employ Russinovich's Sysinternals tools—the command-line "Handle" utility or the graphical "Process Explorer"—which reveal which processes are locking files.