OneDrive takes up local hard drive space because, on default settings, it keeps a full copy of every synced file on your C: drive in addition to the cloud — so a 500 GB OneDrive can fill 500 GB of disk. The fix is Files On-Demand: right-click the OneDrive folder in File Explorer and choose Free up space to turn local copies into online-only placeholders. It reclaims the disk space instantly and never touches the cloud copy.
TL;DR
- By default OneDrive stores a local copy of every file, so cloud size equals disk usage.
- Files On-Demand lets files live in the cloud as ~0-byte placeholders until you open them.
- To reclaim space, right-click a OneDrive folder or file and choose Free up space.
- Free up space never deletes anything from the cloud; it only removes the local cached copy.
- Files marked Always keep on this device stay on disk; unpin them to let Windows evict them.
Why is OneDrive on my C: drive at all?
OneDrive is built into Windows as a sync client, not just a website, so it mirrors your cloud folder to a local folder on the C: drive. That local mirror is what lets you open files offline and have edits sync back automatically. The downside is that, with the default setting, every file is downloaded and cached locally, meaning your cloud storage and your disk usage are effectively the same number. If you store 300 GB in OneDrive, that is 300 GB of your hard drive gone until you change how files are stored.
How does Files On-Demand work?
Files On-Demand is the Windows feature, on by default, that lets OneDrive files exist in the cloud without occupying disk space until you need them. Every file has one of three states, shown as an icon in File Explorer:
| Status | Icon | Disk usage | Behavior |
|---|---|---|---|
| Online-only | Blue cloud | ~0 bytes | Streams from the cloud when opened |
| Locally available | Green checkmark (outline) | Full file cached | Cached after you opened it; can be evicted later |
| Always keep on this device | Solid green checkmark | Full file, pinned | Stays on disk, never evicted automatically |
When you open an online-only file, Windows downloads it on demand and it becomes locally available. Close it and Windows may evict it again later to reclaim space.
How do I free up space without breaking OneDrive?
Use the built-in Free up space command, which strips the local copy while leaving the cloud copy intact:
- Open File Explorer › OneDrive.
- Right-click a folder or file and choose Free up space.
- The status icons switch from green checkmarks to blue clouds.
- The disk space is reclaimed immediately, with the cloud copy untouched.
If Free up space is missing from the menu, Files On-Demand is turned off. Re-enable it:
- Click the OneDrive cloud icon in the system tray.
- Go to Settings (gear) › Settings › Sync and backup › Advanced settings.
- Toggle Files On-Demand to On.
- Right-click the folder again; the Free up space option now appears.
Is making files online-only safe?
Yes. Choosing Free up space is safe and fully reversible: it removes only the local cached copy, never the file in the cloud, and the file reappears on disk the moment you open it again. The one caveat is offline access, because an online-only file needs an internet connection to open. If you travel or work offline, right-click the files you will need and choose Always keep on this device first. Nothing is deleted in either direction; you are only choosing where each file is stored.
Why does OneDrive still take space after I free it up?
If disk usage stays high after running Free up space, the likely cause is pinned files. Anything marked Always keep on this device never evicts, so right-click those folders and either run Free up space (which overrides the pin on contents) or toggle Always keep on this device off. Also check the OneDrive Recycle Bin, since deleted cloud files still count against your cloud quota even though they no longer use disk. For the rest of a Windows cleanup, continue with deep cleaning Windows 11 and 10 without third-party utilities, then reclaim more with how to disable hibernation to save gigabytes of space and how to clear Delivery Optimization files. If you are unsure what else is large, what is the AppData folder and can I delete it clears up another common space hog, and the cross-platform catch-all storage space running out: how to check what's taking up space shows how to find the biggest files. The free up phone storage hub covers the mobile side when your phone fills up too.
Related: what actually fills up phone storage in 2026 · the apps people blame for full storage
FAQ
Does OneDrive store files on my computer or only in the cloud?
By default OneDrive stores a full local copy of every synced file on your C: drive as well as in the cloud, so disk usage matches your cloud size. Files On-Demand lets you change this so files stay online-only until opened.
Does "Free up space" delete my OneDrive files?
No. Free up space removes only the local cached copy and converts the file to an online-only placeholder. The cloud copy is untouched, and the file downloads again automatically when you open it.
How do I make OneDrive files online-only?
Right-click a OneDrive folder or file in File Explorer and choose Free up space. Its icon changes from a green checkmark to a blue cloud, and the disk space is reclaimed immediately while the cloud copy stays safe.
Why is OneDrive still using disk space after Free up space?
The usual reason is files pinned with Always keep on this device, which never evict. Right-click those folders to run Free up space or toggle the pin off. Also empty the OneDrive Recycle Bin to clear cloud quota.
Can I open online-only OneDrive files offline?
No. An online-only file needs an internet connection to download when you open it. If you need a file offline, right-click it and choose Always keep on this device before you go offline.
Once your PC is sorted, keep your phone just as lean with the privacy-first Cleanor app for iPhone, which finds large files and duplicate photos locally without uploading anything to the cloud.