Files-On-Demand status on OneDrive for Mac is confusing

Question

Setting the scene: I'm on an M1 MacBook Pro, MacOS Sequoia 15.5, OneDrive for Mac v.26.017.0126.0002 (standalone)

Mystery #1:

Okay, so I've got a folder chock full of large files (all neatly placed in nested subfolders, of course). This one folder totals about 400 GB, in fact. For obvious reasons I had set that folder to be cloud-only by electing it and choosing 'Free Up Space' from the contextual menu. It took a while to unload all that data but eventually my finder window showed '900 GB available' instead of '500 GB available', which is what it has said previously. Great. 

Except that when I looked at the actual folder in ~/Library/CloudStorage and used Cmd-i to 'Get info' on that folder, the info window said that the folder size was… 400GB. The third party disk analysis tool Daisy Disk also reported that folder as being 400 GB in size.

Surely if the files have been released back to the cloud and only placeholder 'stubs' remain on the local file system, that folder should have a much smaller size. So what's up?

Mystery #2:

I want to make a cloned copy of my Mac for backup purposes and I want to include my OneDrive content in that backup (in case the Microsoft OneDrive servers explode, or get overrun by fire ants, or something). I know that there's no point backing up the placeholder stubs — they've got no real data in them (or do they? See Mystery #1) so I select that big old 400GB folder and select 'Always keep on this device'. The menubar icon shows activity, and I can see the individual files downloading if I click that menubar icon. About 20 hours later (because 400 GB) OneDrive finally reports 'Your files are synced'. And the Finder, sure enough, tells me that I now only have 500GB available, not 900 GB.

HOWEVER, that folder, and each folder and file inside that folder, has both a 'downloaded locally' checkmark icon (dark grey) AND a 'in the cloud'/'do you want to download this?' icon (cloud with a downward arrow in it). Cmd-i (Get info) on one of the subfolders reports a theoretical size for that subfolder of ~230 GB but with only 11.4 MB on disk. Surely, at this stage, size on disk should match the full size of the folder, not a fraction of it, right? I mean, OneDrive did just supposedly spend 20 hours downloading all the data.

But if I click on the cloud-with arrow icon then OneDrive seems to redownload the file or folder-and-contents. At least I assume that that's what it's doing; this time the OneDrive menubar icon does NOT show activity, nor do any files show as being processed/downloaded if I open up that menubar window. But the cloud-with-arrow icon turns into one of those 'time-remaining' icons that looks like a pie chart being filled up and, whatever the process is, it seems to take about as long as I would expect the download to take (a few minutes to download a GB or so on my connection).

So far I've only done this with small folders, as an experiment, because if I'm right about what's going on then that 230 GB folder will be showing that pie chart icon for a LOOOONG time. 

So WTF is going on? If 'Always keep on this device' hasn't actually downloaded the full-fat versions of my files then what the heck was OneDrive doing all through the night and the whole of today? Pretending to download it just to mess with me?

Do I actually have to download all this data twice?

Can somebody either explain how and why this is the way that OneDrive is supposed to work (I can't believe that it is), or tell me what I'm doing wrong, or suggest a solution? Or even just confirm to me that I've not gone crazy?

Answer 1

Hello Rick Lecoat,

Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data. 

Thank you for posting your question in the Microsoft Q&A forum!

I understand that you are confusing with Files-On-Demand status on OneDrive for Mac. I truly understand how you feel. Let me assist you go through this situation.

What you’re actually seeing (the core model)

On modern macOS (Monterey 12.1 > Sequoia 15.x), OneDrive no longer controls files directly. Apple does.

OneDrive is forced to use Apple’s File Provider system, which fundamentally changes what “downloaded” means.

There are three distinct states now — Finder icons blur them together:

1. Placeholder only
   • Logical file exists
   • Advertises full size (e.g. 230 GB)
   • Uses almost no disk
2. Offline‑eligible
   • Marked as allowed to be local
   • Still may not contain real data
3. Hydrated
   • Real file data exists on disk
   • Disk usage matches file size

Finder gives you icons for (1) and (2), but only (3) is real data.

Mystery #1 — why “Free up space” still shows 400 GB

When you used Free Up Space:

• OneDrive deleted the local file data
• macOS kept sparse placeholder files

Sparse files:

• Report their logical size (400 GB)
• Allocate disk blocks only when read

So:

• Finder “Size” = logical size (lies)
• Finder “Size on disk” = actual blocks (truth)
• Available space jumping from 500 GB > 900 GB proves the data is gone

Disk tools (including DaisyDisk) often misinterpret sparse files and show phantom usage. This is a macOS limitation, not hidden data.

Mystery #2 — what “Always keep on this device” actually did

When you set the folder to Always keep on this device:

What you thought: “Download everything.”

What actually happened:

• OneDrive told macOS: these files are allowed to be local
• macOS created offline‑eligible placeholders
• OneDrive synced metadata and file structure
• Actual file contents were not guaranteed to download

That’s why:

• You saw 20 hours of “sync”
• Your free space dropped (some files did hydrate)
• But folders still show checkmark and download icon
• And “230 GB” folders only had ~11 MB on disk

This state is officially described as “unopened offline cloud files”.

I hope this will help with your situation. Please feel free to reach back if you have further update or more questions.

Best Regards,

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