I bought a 128GB stick to back up my MacBook Air (Time Machine). This way I don't need to re-format my external HDD I use for backing up files from my Windows machine. Since I won't be using the stick with my Windows machine I thought I might format it with a "better" file system than exFat. Would you recommend formatting it to HFS+?

  • You could have partitioned your old HDD and used it for two different file systems at the same time. You could install a HFS+ driver on your Windows machine to access the HFS+ partition from there too. HFS+ is required for TM.
    – Fiksdal
    Commented May 21, 2016 at 20:22

3 Answers 3


From Apple KB : Backup disks you can use with Time Machine

Formatting a backup disk for use with Time Machine

The most common format for a Time Machine backup disk is Mac OS Extended (Journaled) format.

Time Machine also supports Mac OS Extended (Case-sensitive, Journaled), Mac OS Extended (Case-sensitive, Journaled, Encrypted), and Xsan formats.
If your disk uses the Master Boot Record (MBR) partition type, some partitions might not be available for use with Time Machine.

In short, use a Journaled HFS+ partition on a GUID[GPT] formatted disk for best results.


For macOS Big Sur 11.0 and newer

Since macOS Big Sur, the best file systems to use for Time Machine backups are APFS and APFS Encrypted, as mentioned in the macOS User Guide:

APFS or APFS Encrypted disks are the preferred format for a Time Machine backup disk. If you select a new backup disk that’s not already formatted as an APFS disk, you get the option to erase and reformat it. If the disk is a Mac OS Extended format disk that contains an existing Time Machine backup, you aren’t asked to erase and reformat the disk.


If you want to use your USB stick for multiple operating systems (like Windows, Mac, Linux), then you should format your USB stick in the following way:

  • If your USB is <= 4 GB, then format with FAT
  • If your USB is <= 32 GB, then format with FAT32
  • If your USB is <= 64 GB, then format with exFAT

NTFS and APFS/HFS are only for Windows and macOS respectively, don't use this if you want to use it on multiple operating systems.

This mostly worked for me.

  • 1
    But Time Machine only works on HFS and APFS so you can't use a FAT based format
    – mmmmmm
    Commented Feb 10, 2022 at 10:07

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