Keep the folder tree but not the bytes: what each icon means, how to dehydrate a large directory in one command, and how to pin what must work offline.
Right-click a folder and pick **Free up space** to turn files into cloud placeholders. `attrib +U -P /s` does the same for a whole tree, and **Always keep on this device** pins the files you need offline.
Files On-Demand is a property of the sync engine. Without it every file is a real file and no placeholder can exist.
reg query HKCU\Software\Microsoft\OneDrive /v FilesOnDemandEnabledA cloud means online only, a green tick means downloaded and pinned, two blue arrows mean syncing. Opening a cloud file downloads it and turns the icon into a tick, which is how the folder grows again without a warning.
The context menu action dehydrates everything inside and leaves the names and the structure in place. The files stay in the cloud, only the local copy disappears.
Right-click > Free up spaceThe attribute tool changes the pin state for a whole directory without opening it. U means unpinned, P means pinned, and s makes it recursive.
attrib +U -P /sThe reverse command downloads everything below the current directory and keeps it. Do this before a flight or a trip, not on the train.
attrib -U +P /sMeasure the folder after the sync engine has finished, not while it is still releasing blocks. Explorer shows size on disk next to size, and the gap between them is what you gained.
Get-ChildItem $env:USERPROFILE\OneDrive -Recurse -File | Measure-Object Length -SumThe location is not NTFS or not local. A FAT32 stick or a mapped network folder cannot hold placeholders.
OneDrive crashed. Restart it from the tray, and use OneDrive.exe /reset if the error comes back.
Pending uploads keep the local copy alive. Wait for the sync to finish, then dehydrate again.
Storage Sense with the OneDrive rule can dehydrate pinned files. Turn that rule off in Storage settings.
Normal reads work. Backup tools that copy the raw stream can upload the placeholder instead of the content.
Yes. The placeholder is the file, and it goes to the OneDrive recycle bin.
attrib -U +P /s inside the folder downloads every file again. Turning the feature off in OneDrive settings keeps the local copies and stops new placeholders from being created.
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