I've experienced hard to ignore folders without synchronization.
I use oneDrive for source repository. When I build my projects, oneDrive client try to synchronize thousands of files. So I unchecked build and target folders in Settings, remove them in online site. But after building project, oneDrive client alerts Synchronization Problem with red exclamation mark.
I really hope oneDrive support .ignore file like .gitignore
Sounds like you're talking about the OneDrive sync client. Since this is a feature suggestion, can you add it on the onedrive uservoice page: https://onedrive.uservoice.com/forums/262982-onedrive
For anyone else finding this from a Google search, this is the issue that needs your votes: https://onedrive.uservoice.com/forums/913522-onedrive-on-windows/suggestions/18449926-reassess-the-possibility-to-ignore-or-exclude-sele
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For anyone else finding this from a Google search, this is the issue that needs your votes: https://onedrive.uservoice.com/forums/913522-onedrive-on-windows/suggestions/18449926-reassess-the-possibility-to-ignore-or-exclude-sele