Where apps hide your files

Office caches and UBF8T346G9.Office

Updated 2026-10-28 · 6 min read

Word, Excel and PowerPoint do not use one cache folder. Their data is split between a shared group container and one container per app, and only the add-in cache has official clearing steps. Here is what each folder holds and what can go.

The folders

~/Library/Group Containers/UBF8T346G9.Office
~/Library/Containers/com.microsoft.Word
~/Library/Containers/com.microsoft.Excel
~/Library/Containers/com.microsoft.Powerpoint
~/Library/Containers/com.microsoft.Outlook

UBF8T346G9 is Microsoft's Apple developer team identifier, and UBF8T346G9.Office is the group container all Office apps share. Each app also has its own sandbox container named after its bundle identifier, with the real files under Data/Library inside it.

Open any of them with ⇧⌘G in Finder. One trap, which Microsoft's own cache guide points out: when you browse ~/Library/Containers in Finder, the folders are shown by product name, such as Microsoft Excel, not com.microsoft.Excel. Go to Folder with the full path avoids the confusion.

What each one holds

These names were listed on a Mac running macOS Sequoia that held Microsoft 365 data from an earlier install (the Office apps themselves had since been removed):

Where	What it contains
UBF8T346G9.Office/FontCache	Font data shared by the Office apps
UBF8T346G9.Office/SolutionPackages	Packages Office downloads for its own features; about 164 MB here
UBF8T346G9.Office/Outlook	Outlook 15 Profiles, where legacy Outlook keeps its profile and mail data. Not a cache
UBF8T346G9.Office/User Content.localized	Your templates, themes, style sets and Normal.dotm. Not a cache
UBF8T346G9.Office/Licenses, MicrosoftRegistrationDB	Activation and registration. Not a cache
<app container>/Data/Library/Application Support/Microsoft/FontPreviewCache	Font preview images
<app container>/Data/Library/Application Support/Microsoft/GraphicsCache	Cached graphics (Word, PowerPoint)
<app container>/Data/Library/Application Support/Microsoft/Temp	Temporary working files (Word, Outlook)
<app container>/Data/Library/Preferences/AutoRecovery	AutoRecover copies of open documents (Word, PowerPoint)

Excel is the odd one out: its AutoRecover files (names starting ~ar and ending .xar) sit directly in its Application Support/Microsoft folder, next to its caches. On the checked Mac that folder also held several large folders named after workbooks that had been open. Treat anything there as possible recovery data until you have checked it.

The standard Data/Library/Caches folder inside each app container was empty on the checked Mac, which is why "clear the cache" guides send you elsewhere.

The cache Microsoft documents: Office add-ins

The only Office for Mac cache Microsoft publishes clearing steps for is the add-in cache. Its guide says to delete the contents of:

~/Library/Containers/com.Microsoft.OsfWebHost/Data/
~/Library/Containers/com.microsoft.Word/Data/Documents/wef

and the same wef folder in the Excel and PowerPoint containers. If the first folder does not exist, the guide lists alternatives, including Data/Library/Caches/ and Data/Library/Application Support/Microsoft/Office/16.0/Wef/ inside each app's container. Microsoft warns to clear the cache completely rather than deleting individual manifest files, which can stop all add-ins loading. For a single add-in in Word, Excel or PowerPoint, the add-in task pane's personality menu has Clear Web Cache.

How big it gets

Measure before you delete:

du -sh ~/Library/Group\ Containers/UBF8T346G9.Office
du -sh ~/Library/Containers/com.microsoft.Word ~/Library/Containers/com.microsoft.Excel
du -sh ~/Library/Containers/com.microsoft.Powerpoint ~/Library/Containers/com.microsoft.Outlook

On the checked Mac the totals were about 289 MB for the shared container, 39 MB for Word, 348 MB for Excel, 65 MB for PowerPoint and 1.5 GB for Outlook. Outlook is normally the big one because it keeps mail locally; that is not a cache, so do not clear it to save space.

Finding what is actually big

This command reads names and sizes and changes nothing:

find ~/Library/Containers/com.microsoft.Excel ~/Library/Containers/com.microsoft.Word -maxdepth 7 -size +50M

Change the apps to suit. A single big file usually tells you more than a folder total.

What can be cleared, carefully

Microsoft does not document the folders below, but their names and contents mark them as caches. Clear them only with every Office app closed (⌘Q each, including Outlook):

• FontPreviewCache and GraphicsCache contents.
• Temp contents, when no document is open.
• FontCache, in the shared container or an app's own container. Expect the next launch to be slower.

Use Finder and move items to the Trash rather than using rm. Move one folder at a time, relaunch the app, and put it back if something breaks. Leave the Trash unemptied for a day or two; until then the moved items are your undo.

What not to clear

• AutoRecovery folders and Excel's .xar files: unsaved work waits there until you reopen the app. Recover what you need first.
• User Content.localized: your templates and Normal.dotm.
• Licenses, MicrosoftRegistrationDB and the .plist files at the top of the group container: activation and settings.
• Outlook, in either location: mail and profiles.
• Whole container folders. Trashing com.microsoft.Word removes the app's settings and data at once and can force you to sign in again.

If Office is misbehaving

A common step for crashes at launch is to quit the apps and move the app's preferences file to the Desktop so it is recreated. For Word it is Data/Library/Preferences/com.microsoft.Word.plist inside the Word container. Try that before clearing caches, because it is easier to undo.

Why the files are invisible to search

Spotlight does not show results from Group Containers or app containers; on the checked Mac, mdfind returned nothing from either. Many Office cache files also have hex-style names with no extension.

Finding the folders again

With Full Disk Access, Everywhere can see inside group and app containers, so typing UBF8T346G9 lists every Microsoft group container at once and typing FontPreviewCache or wef jumps straight to those folders. Press ⌘↵ to reveal one in Finder before deciding what to move. It matches names, so it shows where space is hiding, not what the files contain.

Common questions

What is UBF8T346G9.Office on my Mac?

It is the group container shared by Word, Excel, PowerPoint and Outlook, in ~/Library/Group Containers. UBF8T346G9 is Microsoft's developer team identifier.

Where is the Office cache on a Mac?

Font and graphics caches sit in each app's container under Data/Library/Application Support/Microsoft, with more in the shared UBF8T346G9.Office folder. The add-in cache Microsoft documents is in com.Microsoft.OsfWebHost/Data and each app's Data/Documents/wef folder.

Is it safe to delete the Office cache?

Clear only cache folders, with every Office app closed, and move them to the Trash so you can undo. Leave AutoRecovery, Excel's .xar files, Outlook, Licenses and your templates alone.

Does clearing the cache fix Word crashes?

Sometimes, but moving Word's preferences file out so it is recreated is the more common first step. Move rather than delete, so you can restore it.