Can I completely disable Cortana on Windows 10?
Source : Super User [windows-10].)
The easiest way to disable certain privacy aspects of Cortana is to use a third-party tool such as O&O Software’s free ShutUp10.
Part of Cortana, though, is Windows Search, so there would still be an occasional Cortana process such as file indexing. However, there should no longer be any use of the internet by Cortana.
You can remove Cortana completely, if you wish, but that also removes Windows Search (though that might not be an issue if you use a third-party tool such as DocFetcher or Mythicsoft’s Agent Ransack, which provide increased search functionality). That said, after a Windows 10 update, expect that Cortana would be reinstalled. Apparently, the only way now to permanently avoid Cortana is to use another OS, such as Linux.