Understanding the Root Cause
The confusion arises because the error message refers to the capacity of individual files rather than the total storage space available. Even though your 128GB flash drive has plenty of free gigabytes, the file system governing how data is organized on that drive imposes limits on single file sizes. The most common file systems used on external drives are FAT32, exFAT, and APFS (or Mac OS Extended).
FAT32 is an older standard that is widely compatible with Windows, macOS, Linux, and gaming consoles. However, its major drawback is a maximum single file size of 4GB minus one byte. If you attempt to copy a video file, disk image, or archive like .tar.bz2 that exceeds this threshold, macOS will block the operation immediately, displaying the specific error message you encountered. This is not a hardware failure but a software limitation inherent to the FAT32 specification.
In contrast, exFAT was designed specifically to overcome these limitations while maintaining broad compatibility across different operating systems. It supports virtually unlimited file sizes, making it ideal for transferring large media files between Macs and PCs. APFS is the modern default for internal Mac drives and offers excellent performance and encryption, though compatibility with non-Apple devices can sometimes be limited depending on the device's firmware.
Backing Up Your Data
Before proceeding with any formatting changes, it is critical to preserve your existing data. Reformatting a drive erases everything currently stored on it. You cannot simply change the format without wiping the partition table. Therefore, you must move all important files from the flash drive to another location, such as your Desktop, Documents folder, or an external hard drive.
- Connect the 128GB flash drive to your Mac.
- Open Finder and locate the drive in the sidebar under "Locations."
- Select all files and folders on the drive by pressing
Command + A. - Drag them to a safe location on your Mac’s internal storage.
- Verify that the transfer completed successfully by checking file sizes and opening a few samples.
Once you are certain that all data is safely backed up elsewhere, you can proceed with reformatting the drive. Do not skip this step; attempting to format without a backup will result in permanent data loss.
Reformatting to exFAT Using Disk Utility
The most straightforward way to resolve this issue on macOS is by using the built-in Disk Utility application. This tool allows you to erase and reconfigure the drive with a new file system. Follow these steps to convert your drive to exFAT:
- Open Spotlight search by pressing
Command + Spaceand type Disk Utility, then press Enter. - In the Disk Utility window, select your 128GB flash drive from the list of devices on the left. Ensure you select the physical drive itself, often listed at the top level, rather than just the volume underneath it.
- Click the Erase button in the toolbar. This action will prepare the drive for a new format.
- A dialog box will appear asking for details about the new format. Leave the name as default or give it a recognizable name.
- For the Format dropdown menu, select exFAT. This is the recommended choice for cross-platform compatibility with large files.
- If you see a Scheme option, ensure it is set to GUID Partition Map. This is generally the best practice for modern external drives, especially if you plan to use them with both Mac and PC.
- Click Erase to begin the process. Wait for the progress bar to complete and the drive to disappear and reappear in the sidebar.
This process typically takes only a few minutes. Once finished, your drive will be empty but ready to accept files larger than 4GB. You can now drag your .tar.bz2 file or other large media back onto the drive. The operation should complete without errors.
Alternative: Formatting as APFS
If you only intend to use the flash drive with Mac computers and never with Windows PCs or other devices, you might consider formatting as APFS instead of exFAT. APFS offers faster file copying speeds and better resilience against corruption. However, Windows machines cannot read APFS drives natively, and some older Android devices may also struggle to recognize them. For general-purpose large file transfers, exFAT remains the safest and most versatile option.
Troubleshooting Persistent Errors
If you still encounter issues after reformatting, check the following. First, ensure the drive is properly ejected before unplugging it. Second, verify that the drive is not write-protected; some physical switches on USB sticks can lock the drive. Third, try a different USB port or cable, as faulty connections can sometimes cause incomplete writes that mimic capacity errors. If the problem persists, the drive itself may have bad sectors, and replacing it might be necessary.
Frequently Asked Questions
Can I keep my data and just change the format?
No, changing the file system requires erasing the entire drive. There are third-party tools that claim to convert formats without data loss, but they carry a high risk of corruption. The only safe method is to back up your files, reformat, and restore them.
Why does my drive show as FAT32 even though it is 128GB?
Many manufacturers pre-format drives as FAT32 to ensure immediate plug-and-play compatibility with Windows, Linux, and car stereos. They do this despite the 4GB limit because user experience with universal compatibility often outweighs the needs of large file transfers for average users.
Is exFAT slower than FAT32?
Performance differences are negligible for typical flash drive usage. exFAT may have slightly higher overhead due to its more complex structure, but in practice, you will not notice a speed difference when copying large files compared to FAT32.
What if I need to use the drive on a Windows PC?
exFAT is fully supported by Windows Vista SP1 and later versions. If you format the drive as exFAT on your Mac, you can plug it into a Windows PC and copy files larger than 4GB without any issues.
How do I check the current format of my drive?
Select the drive in Disk Utility and look at the "Format" field in the main window's info panel. Alternatively, right-click the drive icon in Finder, select Get Info, and look for the "Where" or "Format" section in the details list.