Why can’t I encrypt my flash drive Mac?

There are a few reasons why you may be unable to encrypt your flash drive on a Mac. In this article, we’ll explore the most common issues and how to resolve them.

MacOS Version

The first thing to check is your version of MacOS. Full disk encryption for external drives is only supported in MacOS 10.7 Lion and newer. If you’re running an older version of MacOS, you won’t have the option to encrypt external drives.

To check your MacOS version, go to the Apple menu and choose About This Mac. You’ll see the macOS name and version number. If you’re running anything older than 10.7, you’ll need to update your OS to enable full disk encryption.

Format of the Flash Drive

The next thing to verify is the format of your flash drive. In order to encrypt a drive on a Mac, it must use the GUID Partition Table (GPT) format. This is a different format than Master Boot Record (MBR), which is the older format used by PCs.

You can check the format of your flash drive by opening Disk Utility. Select your flash drive in the sidebar, then check the Partition Map Scheme listed. If it says Master Boot Record instead of GUID Partition Map, your drive will need to be reformatted before it can be encrypted.

To reformat the drive, select the drive in Disk Utility and click Erase in the toolbar. Choose GUID Partition Map for the Scheme and Mac OS Extended (Journaled) for the format. This will reformat the drive into a Mac compatible format.

Flash Drive Capacity

There are also limits on the drive capacity when encrypting external drives on a Mac. Full disk encryption works only for drives between 128MB and 2TB in size. If your flash drive is outside this range, you won’t be able to fully encrypt it.

You can check the capacity by selecting the flash drive in Finder and looking at the size listed. If it’s less than 128MB or over 2TB, encryption won’t be an option unfortunately.

Password Setting Errors

If your flash drive meets the requirements for encryption, the next issue may be setting the password. Sometimes there are errors that occur which prevent setting a password properly.

First, make sure your password meets the requirements. It must be at least 8 characters long and contain capitals, lowercase, numbers, and symbols. If you’re still getting errors, try resetting the NVRAM on your Mac as that can clear out stuck settings.

To reset NVRAM, restart your Mac and hold down Command + Option + P + R. Keep holding the keys until you hear the startup chime again, then release. After resetting NVRAM, try setting the encryption password again.

Insufficient Permissions

You also need to have administrative privileges enabled to be able to encrypt a drive. Standard user accounts don’t have the permissions to turn on encryption.

To check your account permissions, open System Preferences then click Users & Groups. Select your user account and make sure you’re listed as an Admin user. If not, click the lock icon to make changes, then enable administrator permissions.

Now when you restart your Mac and attempt drive encryption, it should allow you to set a password without issue.

Corrupted Encryption Process

Sometimes the encryption process itself can become corrupted and fail to complete properly. This will prevent access to the drive afterward.

If this happens, you’ll need to remove and reformat the flash drive, then start over with the encryption process. Be sure to back up any data on the drive first.

To remove the corrupted encryption, open Disk Utility and select the flash drive. Click Erase and choose Mac OS Extended (Journaled) as the format. This will wipe the drive completely.

Then start the encryption process again from the beginning. Go slowly to be sure the encryption completes fully before ejecting the drive.

Using a Windows Encrypted Drive

If your flash drive was encrypted on a Windows PC, that encryption often won’t be recognized by Mac. Windows uses NTFS formatting and encryption by default, while Macs rely on FAT32 or exFAT for flash drives.

To use a Windows encrypted drive on your Mac, you’ll need to decrypt the drive first using a PC. Then format the drive using the Mac compatible format FAT32 or exFAT. At that point, you can encrypt the drive again using your Mac.

Damaged or Corrupt Flash Drive

Sometimes drive encryption failures are due to a damaged, worn out, or corrupt flash drive. As flash memory wears out over time, it becomes less reliable for reading and writing data.

Try testing your flash drive using Disk Utility. Select the drive, click First Aid, then Run. This will scan for and attempt to repair errors on the drive.

If the repair fails or the drive is severely damaged, it may need to be replaced. Encryption requires reliable media to work properly.

Using Third Party Encryption Tools

If the built-in Mac encryption isn’t working, you can try using a third party encryption tool instead.

Popular options include VeraCrypt, Cryptomator, and LaCie Private-Public. These tools may provide more options for encrypting flash drives, though the process is usually more involved.

Make sure to research the encryption tool first and understand how to use it properly. Follow all steps to encrypt and unlock the drive to avoid data loss.


While Macs make it easy to encrypt flash drives, sometimes issues come up that prevent it from working properly. By understanding the requirements and troubleshooting common problems, you should be able to resolve encryption failures.

The key steps are:

  • Update to MacOS 10.7 Lion or newer
  • Use GPT partition format on the flash drive
  • Stay within size limits of 128MB to 2TB
  • Use a strong 8 character minimum password
  • Ensure you have admin account permissions
  • Try resetting NVRAM if the password won’t set
  • Reformat corrupted drives and restart encryption
  • Decrypt Windows encrypted drives first before using on a Mac
  • Replace damaged or worn out flash drives
  • Use third party encryption tools if built-in options fail

Following this troubleshooting guide should help get your flash drive encrypted properly. Just take it slowly and systematically to isolate any issues. With some perseverance, you should be able to encrypt nearly any flash drive on your Mac.

MacOS Version Encryption Support
10.7 Lion and newer Full disk encryption supported
Older than 10.7 No full disk encryption
Partition Format Encryption Support
GUID Partition Table (GPT) Supported
Master Boot Record (MBR) Not supported
Drive Capacity Encryption Support
128MB to 2TB Supported
Less than 128MB Not supported
Over 2TB Not supported
Account Permission Encryption Access
Administrator Full access
Standard user No access
Encryption Tool Platform
Built-in Mac encryption Mac only
VeraCrypt Mac and Windows
Cryptomator Mac, Windows, Linux, mobile
LaCie Private-Public Mac and Windows

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