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Fix OneDrive Files Damaged When Copied on Mac to External Drive
Question details
The user needs to prevent OneDrive files from becoming corrupted or incomplete when transferring them from a Mac to an external hard drive.
- Product
- Microsoft OneDrive
- Device & OS
- macOS
- Scenario
- Copying synchronized OneDrive data from a Mac local folder to an external backup drive.
- Observed behavior
- Copied files appear corrupted or fail verification, some online files report zero size, and sync discrepancies occur where locally deleted folders still appear on the OneDrive website.
Ensure your Mac has a stable internet connection so incomplete cloud files can be downloaded, and pause any active sync tasks to prevent conflicts during the backup process.
Download Files Locally Before Copying
Ensure files are fully downloaded to your Mac by disabling Files On-Demand or marking them for offline use before copying them to an external drive.
The most common reason for file corruption during a transfer is Microsoft's 'Files On-Demand' feature. When enabled, Mac Finder only stores placeholders for your files. Copying these placeholders directly to an external drive results in empty or damaged files.
Click the OneDrive cloud icon in your Mac's menu bar, click the gear icon (Help & Settings), and select 'Preferences'.
Navigate to the 'Sync and back up' or 'Preferences' tab, find the 'Files On-Demand' section, and choose to download all files locally. Alternatively, open Finder, right-click the specific OneDrive folder, and select 'Always keep on this device'.
Wait until the cloud icons next to your files change to solid green checkmarks, indicating that the files are now fully stored on your Mac's hard drive.
Select the fully downloaded files or folders, copy them, and paste them into your connected external drive.
Download Files Directly from the OneDrive Website
If the local OneDrive client is failing to sync properly, bypass the app and download the files directly from the web interface.
Reset the OneDrive Mac Client
Resolve deep synchronization issues and ghost files by completely resetting the OneDrive client on your Mac.
Experience Reliable File Management with WPS Office
If you are frustrated with Microsoft Office cloud sync issues and corrupted file transfers, consider switching to WPS Office. It provides a lightweight, highly compatible, and user-friendly alternative with seamless local and cloud file management.
- 1. Download the Installer: Visit the official WPS website and download the free WPS Office installer for macOS.
- 2. Install and Launch: Open the downloaded package, follow the on-screen instructions to install, and launch the application.
- 3. Manage Files Seamlessly: Open your existing Microsoft formats instantly and save your work securely to your local folders or external drives.
Frequently Asked Questions
Why do my OneDrive files show as zero bytes when copied to an external drive?
This happens when 'Files On-Demand' is active. The file on your Mac is just a cloud shortcut. If you copy the shortcut without downloading the actual file first, the resulting file on your external drive will be empty or corrupted.
How do I know if my OneDrive file is fully downloaded on a Mac?
Look at the status icon next to the file in Finder. A cloud icon with a downward arrow means it is online-only. A solid green circle with a checkmark means the file is downloaded locally and is safe to copy.
Why are deleted files still showing on the OneDrive website?
This indicates a synchronization error between your Mac's OneDrive client and the Microsoft servers. Resetting the OneDrive app or pausing and resuming the sync can force the client to update and match your local state.
