Excel for Mac freezes and reports "out of application memory" every time it launches — fix without reinstalling

TL;DR: If Excel for Mac hangs and your whole Mac reports *"Your system has run

out of application memory"* seconds after launching — with **no workbook even

open** — a single corrupted cache file is likely the cause. Deleting one file

fixes it. Reinstalling does not (the file survives reinstalls).

Symptoms

• Within a few seconds of opening Excel, memory use explodes (I measured ~2–3 GB/second, up to 10–14 GB) and the Mac becomes unresponsive / shows the "out of application memory" dialog.
• Happens on a cold launch, before opening any file.
• Survives a reboot and an ordinary reinstall of Excel.
• Easy to misattribute to low RAM, OneDrive sync, or a big spreadsheet — but none of those is the actual cause.

Environment where I saw it

• Excel for Mac 16.110 (build 16.110.26062818)
• macOS 26.5.2, Apple Silicon, 16 GB RAM
• Work/School (Microsoft 365) account

The cause

Excel keeps a local cache of your "Recent" documents list, synced from the

Microsoft 365 cloud, in this file:

~/Library/Containers/com.microsoft.Excel/Data/Library/Application Support/Microsoft/Office/16.0/MruServiceCache/<account>/Excel/Documents_<locale>

(<account> is a long GUID folder, e.g. ending in _ADAL for work accounts;

<locale> is something like en-US or en-CN.)

If Excel is killed while it is writing this file (an out-of-memory crash, a

force-quit, a power loss...), the file can be left truncated — the JSON ends

in the middle. On version 16.110, when Excel reads a truncated file back on the

next launch, instead of discarding it and re-downloading, it gets stuck

allocating memory without limit. That crashes it again — and because the bad file

is never repaired, every launch repeats the loop.

The fix (takes 30 seconds, loses nothing important)

1. Quit Excel (Force Quit if needed).
2. Delete the cache file. In Terminal:

   
      rm ~/Library/Containers/com.microsoft.Excel/Data/Library/Application\ Support/Microsoft/Office/16.0/MruServiceCache/*/Excel/Documents_*
   
   

   Or in Finder: press ⌘⇧G, paste ~/Library/Containers/com.microsoft.Excel/Data/Library/Application Support/Microsoft/Office/16.0/MruServiceCache/, open the account folder → Excel, and move the Documents_... file to Trash.
3. Launch Excel. It rebuilds a fresh, healthy "Recent" list from the cloud. Your actual spreadsheets are untouched — only the local Recent-files cache is reset.

If you have more than one account folder and aren't sure which is bad, deleting

the Documents_... file in all of them is safe.

Why reinstalling doesn't help

The corrupt file lives in your user data container, not in the Excel app

bundle. Dragging Excel to the Trash and reinstalling from the website leaves the

container in place, so the bad file — and the freeze — comes right back. (A full

uninstall that also clears ~/Library/Containers would work, but that's a

sledgehammer for a one-file problem.)

I reported this to Microsoft

I filed a detailed bug report with a minimal, data-free reproducer. The proper

fix is on Microsoft's side: Excel should discard an unreadable cache and refetch

(it already does this for totally-garbage input — only this one truncation shape

trips it), and it should write the file atomically so an interrupted write can't

corrupt it. Until a fixed build ships, the delete-one-file workaround above

resolves it.

Hope this saves someone the hours it took to track down. Happy to answer

questions below.