Open a BitLocker drive on a Mac

Plug a BitLocker drive into a Mac and Finder offers to erase it. Here is why, and how to read the drive instead.

What BitLocker is

BitLocker is the encryption built into Windows. When it is turned on, everything written to the drive is scrambled, and the contents cannot be read without the password. Windows uses it on its own drive, and on USB drives and memory cards, where it is called BitLocker To Go.

It is the same encryption in both cases. If the drive is lost, whoever finds it cannot read anything on it.

What happens when you plug one into a Mac

Finder says the disk is unreadable and offers to initialise or erase it. It does not ask for a password, and nothing on screen suggests the drive is locked rather than broken.

The drive is not damaged. macOS has its own encryption, FileVault, and does not understand BitLocker at all. It reads the beginning of the drive, finds a layout it does not recognise, and treats the disk as unformatted, so the only thing it can offer is to erase it.

How Lukotta opens it

Linux has been able to read BitLocker for years, and that is what Lukotta uses. It starts a small Linux system in the background, hands it the drive, and unlocks it there with the password you type. The unlocked drive goes back to Finder, where it appears under Locations alongside your other disks.

The drive is not converted or copied. It stays a BitLocker drive, still encrypted, and Windows still reads it.

Opening the drive

1. Plug in the drive. Lukotta lists it and shows it as locked.
2. Click it and type the password you use on Windows.
3. The drive appears in Finder under Locations.

If you do not have the password

When the drive was encrypted, Windows generated a recovery key and asked where to keep it. It opens the drive in place of the password. It is 48 digits, in eight groups of six:

123456-789012-345678-901234-567890-123456-789012-345678

It may be saved in a Microsoft account, in a text file, or printed on paper. Paste it where the password would go.

Without the password or the key, the drive cannot be opened by any program, on any computer.

Drives that will not open on a Mac

Some Windows PCs never ask for a password. They keep the key in a chip on the motherboard, called a TPM, and unlock the drive automatically when that machine starts.

A drive set up that way only works in the PC it came from, because the key never leaves it. No Mac can open it, and neither can another PC. If a recovery key was saved when the drive was encrypted, that will still open it.

Copying files onto the drive

BitLocker drives open for reading and writing, so a Mac can add files to a Windows backup rather than only take them off.

Lukotta can also open the drive read-only, which is worth doing when you are recovering files from a drive that has been playing up. Nothing can be written to it then.