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How to Recover an XLSX File Corrupted by Microsoft 365 for iOS and iCloud
Question details
The user needs to recover an Excel file stored in iCloud Drive that became corrupted and reduced to 66 KB after being accessed with the Microsoft 365 app on an iPhone or iPad.
- Product
- Microsoft 365 for iOS, iCloud Drive, Excel
- Device & OS
- iOS
- Scenario
- Opening and editing an iCloud-stored XLSX document using the Microsoft 365 mobile app on an Apple device.
- Observed behavior
- The file size unexpectedly reduces to approximately 66 KB, and the document can no longer be opened on Mac, Windows, or iOS, displaying an invalid format or extension error.
Immediately stop making edits to the corrupted 66 KB file and do not overwrite it, as preserving its current state increases your chances of retrieving an intact earlier version.
Restore a Previous Version from iCloud or Mac
Use Apple's built-in file history features to retrieve an uncorrupted version of your workbook before the Microsoft 365 app modified it.
Since the mobile app uploaded an incomplete 66 KB file, the easiest way to recover your data is to revert to a previously saved version through iCloud or your Mac's version history.
If you have a Mac synced with iCloud Drive, open a blank document in Excel or Numbers, go to 'File' > 'Revert To' > 'Browse All Versions', and locate the iCloud file to see if an older version is cached.
Log into iCloud.com on a web browser. Click the App Launcher icon, select 'Data Recovery', and look under 'Restore Files' to see if an intact version of your XLSX file is available to download.
On iCloud.com or in the iOS Files app, navigate to the 'Recently Deleted' folder. Sometimes iCloud creates a conflict copy and deletes the original, which might still be sitting in this folder.
Recover the File Using Time Machine Backups
If you sync iCloud Drive to a Mac with Time Machine enabled, you can restore the file from a local backup captured before the corruption occurred.
Use Dedicated Excel Recovery Software
If no backups or previous versions exist, use a dedicated data recovery tool to extract any remaining readable data from the 66 KB file.
Avoid Mobile Sync Errors with WPS Office
Experiencing frustrating file corruption and 66 KB sync bugs in Microsoft 365 for iOS? Switch to WPS Office, a highly compatible, free alternative that seamlessly handles your XLSX files across mobile and desktop without destructive cloud sync issues.
Frequently Asked Questions
Why does my Excel file size change to 66 KB on my iPhone?
This is caused by a known bug in the Microsoft 365 app for iOS when handling files stored in iCloud Drive. The app incorrectly resaves the workbook and uploads an incomplete, truncated version, resulting in a corrupted 66 KB file.
Can I repair the 66 KB corrupted file directly without a backup?
It is highly unlikely. Because the file is severely truncated, the actual data for your worksheets is physically missing from the 66 KB file. Your best option is to restore a previous version from iCloud history or Mac backups.
How can I prevent iCloud Excel file corruption in the future?
To prevent this, ensure both your iOS and the Microsoft 365 app are updated to their latest versions. Additionally, avoid editing critical Excel files directly from iCloud Drive on mobile devices; instead, copy them to local storage first or maintain separate, manual backups.
