There is a hidden registry setting in Windows 10, which when enabled shows the explorer.exe Process ID (PID) in File Explorer title bar, and tells if a folder window is running under the shell process, or as a separate process.
Show Process ID in File Explorer
Start Regedit.exe and go to:
Create a DWORD 32-bit value named ShowPidInTitle
Set the data for ShowPidInTitle to 1
Exit the Registry Editor. Logoff and login back or do a clean restart of the Explorer shell.
Shell process vs separate process
If the folder windows are run under the default Explorer shell, the PID of Explorer shell is displayed – indicated as “shell process: [PID]”
If you’ve enabled Launch folder windows in a separate process option in Folder Options settings, launching folders would create additional explorer.exe instance(s) with a different PID, of course. This also happens if you run explorer.exe [folderpath] directly from Run dialog. In Task Manager the additional instances of explorer.exe appear as shown below, with “/factory” parameter.
In those cases, the title bar would contain the words “separate process: [PID]”.
Not sure how this feature (in Windows 10 Anniversary Update v1607) would help end-users, but thought I’d write about it anyway.
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Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and has a vast experience in Windows — delivering support for Microsoft's consumer products. He has been a Microsoft MVP (2003-2012) who contributes to various Windows support forums.