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Office keeps an offline cache per document, and OneNote never forgets a notebook

Word, Excel and PowerPoint cache every file you open from the cloud, and OneNote stores whole notebooks. Where both are and what clearing costs.

5 min read

Office on a Mac is a cloud client that works offline, and the way it manages that is to keep a local copy of everything you touch. That is a good design and it has a storage consequence nobody mentions.

The places to look

du -sh ~/Library/Group\ Containers/UBF8T346G9.Office \
  ~/Library/Containers/com.microsoft.* \
  ~/Library/Application\ Support/Microsoft 2>/dev/null | sort -h | tail

What each part holds

  • The Office document cache. Local copies of files opened from OneDrive or SharePoint, kept so they open instantly and work offline.
  • AutoRecovery. Snapshots of unsaved work, one per document, which is exactly what you want until the folder is full of files from documents that closed cleanly years ago.
  • OneNote notebooks. Complete local copies of every notebook you have opened, including images and attachments.
  • Per app containers. Each Office application has its own, holding preferences and smaller caches.

Clearing it safely

Office has its own control for this. In the Microsoft Upload Center or, on current versions, in an app's preferences under file locations, there is an option to empty the document cache. Use it rather than deleting folders, because a cached file with unsaved changes is a file you would rather not lose.

For OneNote, closing a notebook removes its local copy. The notebook stays in your account and reopens when you need it, which is the same trade as an online only file in a sync folder.

AutoRecovery is worth a look

du -sh ~/Library/Containers/com.microsoft.*/Data/Library/Application\ Support/Microsoft/Office/*AutoRecovery* 2>/dev/null

Files there belong to documents that were not closed properly. Anything older than a few weeks is from a session you have long since finished, and it is safe to remove once you have confirmed the real document is where you expect it.

Common questions

Where is the Office cache on a Mac?

In the shared group container at ~/Library/Group Containers/UBF8T346G9.Office, with per application containers under ~/Library/Containers. It holds local copies of cloud documents so they open instantly and work offline.

How do I clear the Microsoft Office cache?

Use Office's own option to empty the document cache rather than deleting folders, so files with unsaved changes are not lost. Check that everything has finished uploading first.

Why is OneNote using so much space on my Mac?

Because it keeps a complete local copy of every notebook you have opened, including images and attachments. Closing a notebook removes the local copy and it reopens from your account when needed.

Can I delete Office AutoRecovery files?

Yes, once you have confirmed the real documents are saved where you expect. Those files belong to sessions that did not close properly, and old ones serve no purpose.

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