My MacBook is running Mac OS X Mavericks with FileVault HDD encryption. I use Time Machine to backup this drive to an unencrypted USB HDD.

Will this backup be encrypted? Or does Time Machine decrypt files from my internal HDD and save them in an unencrypted form on the USB HDD?

2 Answers 2


No - Time Machine will not preserve the encryption of the source disk since it reads the files in an unencrypted manner just like any other process once you log in to the Mac.

You would need to ensure that all Time Machine destinations are also encrypted to properly secure your data both on the main computer as well as have it encrypted on the Time Machine volumes. This is as easy as ticking a checkbox on the Time Machine preference pane in system preferences.

On macOS 10.12 Time Machine will throw a helpful notification if you do in fact select an unencrypted destination for encrypted OS.


Mavericks does encrypt backups. From Apple:

The best way to keep your backups secure is to encrypt your backup disk. Encryption is available for Time Capsule, disks attached to another Mac on your network, and disks partitioned with the GPT partition scheme and attached directly to your Mac.

If you want to change from unencrypted to encypted backups, you must remove your backup disk and then set it up again.

So, if you have an existing backup, you'll need to remove them from the backup disk you'd like to be encrypted. You should be able to see the encryption status of your backup on a per-volume basis in the Time Machine pref pane.

  • I’d love for this to become the accepted answer, now that we’re two major revisions of OS X past Mavericks.
    – jeffbyrnes
    Nov 6, 2015 at 15:10
  • @jeffbyrnes the asker doesn't have any activity after asking this question, so it doesn't seem likely.
    – Kellen
    Nov 6, 2015 at 15:27
  • Broken link, by the way. Jul 9, 2022 at 21:20
  • @BasilBourque Yeah, this answer is nearly 8 years old...
    – Kellen
    Jul 12, 2022 at 21:19

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