Three icons, one contract
Every file in a synced OneDrive folder carries a status icon. A blue cloud means the file is online-only: the name and metadata live locally, the content does not, and the file uses no meaningful disk space. A green circle with a white checkmark means locally available — the content was downloaded on demand and stays until the space is needed elsewhere. A filled green circle means always keep on this device: you pinned the file or folder, and OneDrive treats it as permanently local.
The transitions are as often manual as automatic. Open a cloud-only file and it hydrates silently in the background, keeping its green checkmark. Right-click and Free up space reverses the trip — the content goes back to the cloud-only state while the file stays in place, openable and unchanged. Recent Windows builds can even keep only parts of large files local, but the practical effect is the same: the bulk sits in the cloud, and the disk holds what you are actually using.
- A blue cloud icon means online-only: no content on disk, no space used
- Opening or reading a cloud-only file downloads it — that is hydration
- Free up space sends a local file back to cloud-only without deleting anything
- Always keep on this device pins folders you need offline
- Scanners and backup tools that read file contents can hydrate whole libraries
- Storage Sense can free up files you have not opened for a while
The hydration trap
The status icons describe what OneDrive did on purpose; hydration also happens without you opening anything. Any tool that reads file contents — a full antivirus scan, a disk-usage analyzer, a backup program that copies data rather than metadata, a script that hashes entire folders — will pull online-only files down just to read them. Point a naive backup at a 300 GB library that mostly lives in the cloud, and you will watch 300 GB land on your disk before the first backup finishes.
The defenses are boring and effective. Pin only the folders you genuinely need offline; use backup software that understands placeholders; and keep full-content scans pointed at local data. Storage Sense completes the loop by freeing up files you have not opened for a while, quietly undoing accidental hydration. And if a cloud-only file refuses to open offline, that is not corruption — it is the contract working: without internet, there is no content to fetch.
Turning it on, and turning it off
Files on-Demand is switched on in OneDrive's own settings, in the sync section of the help-and-settings menu behind the tray icon — not in Windows Settings, where everyone looks first. If the toggle is missing, sign out of OneDrive and back in, or update the client: older installations and business tenants sometimes carry the feature switched off by policy.
Turning it off deserves a warning: OneDrive then treats your library as always-keep-on-this-device and starts pulling everything down, so check your free space first. Power users flip states from the command line with attrib — unpinning works with +U -P, which is handy for an entire folder tree. Otherwise the right-click menu already scales: Free up space on a folder applies to everything inside it.
Questions and Answers
Do OneDrive Files on-Demand files take up space on my hard drive?
Online-only files (blue cloud) use no meaningful space, while locally available and pinned files do — the status column shows which is which at a glance.
What happens if I turn off Files on-Demand?
OneDrive starts keeping the whole library on this device and downloads it, so make sure you have the disk room before flipping the switch.
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