Every synced file does not have to live on the disk. Files On-Demand keeps the placeholders and downloads content when you open it, which frees gigabytes without breaking anything.
Enable **Files On-Demand** in OneDrive settings, dehydrate a folder with **attrib +U -P /s /d**, and pin the folders you need offline with **Always keep on this device**.
The folder looks the same in Explorer either way. The attribute tells you whether a file has local content: **Offline** means the data is on disk.
$root = "$env:USERPROFILE\OneDrive"
Get-ChildItem $root -Recurse -File -ErrorAction SilentlyContinue |
Measure-Object Length -Sum | Select-Object Count,@{n='GB';e={[math]::Round($_.Sum/1GB,1)}}
(Get-Item "$root\Documents").AttributesThe switch lives in the OneDrive settings under **Save space and download files as you use them**. Without it, the Free up space command removes the local copy permanently instead of leaving a placeholder.
:: OneDrive tray icon > Settings > Sync and backup > Advanced settings
:: or open the settings dialog directly:
%LOCALAPPDATA%\Microsoft\OneDrive\OneDrive.exe /settingsRight-click gives the documented route and shows the state icon afterwards. Use it once to see what a dehydrated folder looks like before you script it.
:: Explorer > right-click the folder > Free up space
Get-ChildItem "$env:USERPROFILE\OneDrive\Archive" -File |
Select-Object -First 3 Name,AttributesThe **+U** attribute marks files as online-only, **-P** clears the pinned flag. Run it in the folder you want to shrink, not at the OneDrive root, or everything including your working set goes remote.
cd "$env:USERPROFILE\OneDrive\Archive"
attrib +U -P /s /d
Get-PSDrive C | Select-Object Used,FreeAnything you open on a plane or during a meeting must be marked **Always keep on this device**. A pinned folder survives the next bulk dehydrate as long as you do not run attrib on it.
cd "$env:USERPROFILE\OneDrive\Work"
attrib -U +P /s /d
(Get-Item .\Project.docx).AttributesCheck the free space and confirm that OneDrive is not stuck processing the change. A paused sync plus dehydrated files is the combination that loses work.
Get-Volume C | Select-Object DriveLetter,@{n='FreeGB';e={[math]::Round($_.SizeRemaining/1GB,1)}}
Get-Process OneDrive | Select-Object Id,CPU,StartTimeFiles On-Demand is off or OneDrive is not running. Restart OneDrive and check the setting again; on exFAT the feature is unavailable.
They are pinned, open in an application, or inside an excluded folder such as an Outlook cache. Close the app and repeat with -P.
The machine is offline or the account needs re-authentication. The placeholder has no content until OneDrive can download it.
Read the numbers again after the sync finishes; the counter lags. If they still match, the files were never local to begin with.
Yes. The file exists as a placeholder and downloads on first access, as long as the account stays signed in.
Not through dehydrating. Delete a placeholder and the file goes to the OneDrive recycle bin like any other deletion.
Turn Files On-Demand off in OneDrive settings and choose Download all files, or pin the specific folders with attrib -U +P /s /d. Local space usage returns to what it was.
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