How to format a USB-Stick – exFAT

Quit possible that you own a USB-Stick (or USB-Hard-Drive) that is 4GB or larger (8GB seems to be standard now,right?).

If you’re not a nerd you probably just used it out of the box. By default all USB-Sticks are formatted as FAT (MS-DOS default) so they work on Windows, Mac and Linux. Yet you might know that there are different types of disk formats. There is also NTFS, (Windows default / does not work on Mac) and there is HFS+ which is the default for Mac OS X.

FAT is by far the oldest file system and has some weaknesses:

  • you can’t put any files larger than 4GB on a FAT disk
  • disks size is limitted to 2TB
  • you can easily lose your data (see footnote)

So maybe you would like to change the file system on your stick to something more modern. But what? Here what I do:

If you use your USB-stick only on Macs you will want to reformat it to HFS+ which allows (virtually) unlimited file sizes, longer file names and some Mac specific things. And it is also much saver in terms of data loss (see footnote).

If you use your stick also on Windows machines running XP SP2, Vista SP1 or Windows 7 you can use the very new file system exFAT. Unfortunately exFAT is only supported on Mac OS 10.6.5 and later. exFAT is very similar to FAT but allows larger file sizes and larger disks (and some other stuff).

So you wonder how to reformat a disk? Quite easy:
In your Applications folder there is a Folder “Utilities” and here you find a App called “Disk Utility”. Open it and you see something like this:

To reformat a disk select it and click the erase tab. Here you can set the disk name and the file system. If you’re ready click “Erase”. That’s it. But make sure you’re not deleting important data. Backup, backup and backup!

Footnote for the technical smart-ass: Why is FAT less secure than others? In short words: HFS+ and NTFS keep track of the changes you make and can recover if an error occurs. FAT and exFAT cannot. If you’re interested in this I can recommend the wikipedia articles. If you’re really interested have a look at the book “Modern Operating Systems” by Andrew S. Tanenbaum

  1. Small correction, Macs can read NTFS, and works with older OS X versions. (that is, you can’t write to NTFS from Mac) Thanks for the article.

    • Luke
    • November 8th, 2011

    Having issues formatting my external 3TB USB drive to exFAT. Mac OS is refusing to format it. I then did a format to exFAT on a Windows 7 computer and my Mac won’t read it!

    Mac OS 10.6.7

    • Luke
    • November 8th, 2011

    Ah wait. I dropped the allocation size down to 1024 and it can be read on my Mac now. Anyone know about limitations with this?

    Great article by the way.

    • That’s very interesting. I don’t have any drives larger than 500MB so I have never experienced problems formatting it on the Mac. Microsoft recommends different cluster sizes depending on the drive size
      According to them one should choose 128kb cluster size for volumes larger than 32GB. So if Apple only supports 1kb cluster size this is really a limitation.
      There is not much known about the internals of exFAT but I can imagine that 1kb cluster size is too little to address a 3TB drive.

      I also found this discussion where people found the same cluster size limitation as you:

      So maybe using exFAT can only be recommended for smaller drives like USB sticks or SD-Cards…
      However I hope Apple will further improve their exFAT implementation.

    • Luke
    • November 10th, 2011

    Cool thanks for the Apple discussion link.

    Hopefully Apple will improve exFAT soon.

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    • Mo
    • November 26th, 2016

    My MacBook Pro will not allow WD 2TB external hard drive to format to EXFAT!
    Any suggestions?

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