How to Fix “Unable to Expand ZIP File” Errors on macOS When Downloading from SharePoint or OneDrive
Downloading large collections of files from SharePoint or OneDrive often results in a single ZIP archive. While convenient in theory, many macOS users encounter the dreaded error message:
“Unable to expand .zip (Error 79 – Inappropriate file type or format)”
This happens when macOS’s built-in Archive Utility struggles with certain ZIP structures. The issue is common with archives generated by SharePoint or OneDrive because they often contain deeply nested folders, very long filenames, or special characters that don’t always play well with macOS.
The good news is there are multiple ways to work around this issue. Below we’ll explore the most effective solutions, along with additional considerations to prevent future headaches.
Why This Error Happens
Several factors can trigger macOS to reject a ZIP file:
- Complex folder structures: Deeply nested directories beyond what Archive Utility can handle.
- Long filenames: SharePoint sometimes exports files with names exceeding macOS’s limits.
- Special characters: Unsupported symbols in file or folder names.
- File size limits: Extremely large ZIPs may not decompress properly.
Practical Solutions
1. Use a Third-Party Extraction Tool
The simplest fix is to bypass Archive Utility and install a more capable decompression tool:
- The Unarchiver (Mac App Store – free)
- Keka (open source)
These tools are more robust at handling OneDrive/SharePoint-generated archives. Simply install one, right-click your ZIP, and choose Open With → The Unarchiver/Keka.
2. Extract via Terminal
If you prefer not to install extra software, macOS includes the unzip command. It’s often more tolerant than Archive Utility.
Open Terminal and run:
unzip ~/Downloads/YourFile.zip -d ~/Downloads/extracted
This will create a new folder named extracted with the contents inside.
3. Re-Download in Smaller Parts
When downloading from SharePoint or OneDrive, you can often select only specific folders or batches of files. Instead of grabbing the entire directory in one massive ZIP, try downloading smaller chunks. This reduces the complexity of the archive and improves your chances of success.
4. Use the OneDrive Desktop App
A better long-term solution is to avoid ZIP files altogether:
- Install the OneDrive sync client for macOS.
- Sign in with your Microsoft account.
- Sync the SharePoint folder directly to Finder.
This way, the files appear on your Mac just like a local folder, without needing to unzip anything.
5. Ask the File Provider for Alternatives
Sometimes the issue lies in how the archive was created. If possible, ask the file provider to:
- Compress the files using 7-Zip or a standard Windows ZIP tool (these often generate more compatible archives).
- Share the folder via direct OneDrive link instead of forcing a ZIP download.
Additional Considerations
- Check Disk Space: Large extractions can fail simply because there isn’t enough storage available. Make sure you have free space greater than twice the size of the ZIP.
- Use External Tools for Very Large Data: If the archive is multiple gigabytes, tools like BetterZip (paid) can help manage the process.
- Watch Out for Sync Conflicts: If you’re collaborating on SharePoint or OneDrive, syncing via the OneDrive client reduces the risk of file mismatches or corrupted downloads.
- Verify File Integrity: Sometimes the download itself is incomplete. Re-downloading the ZIP may solve the problem before you attempt extraction again.
Finally
The “Unable to Expand ZIP” error on macOS is frustrating but solvable. The fastest fixes are using The Unarchiver or Keka, or running unzip in Terminal. For a long-term strategy, syncing with the OneDrive desktop app is the best way to avoid corrupt or incompatible ZIP files altogether.
By understanding the causes and applying one of these solutions, you can reliably access large archives from SharePoint or OneDrive without losing time to extraction errors.
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