Format an External Hard Drive or USB Flash Drive for Mac OS X

Jan 4, 2012 - 42 Comments

Format a hard drive for Mac compatibility If you want to insure full Mac compatibility of a new external hard drive or flash disk, you’ll want to format the drive to the Mac OS Extended filesystem. This is particularly necessary for purchases of generic PC drives, which almost always come preformatted to be Windows compatible rather than for Mac OS X.

Yes, connecting an external hard drive or USB flash key to a Mac will generally read and work fine as is because the Mac can easily read other filesystem formats, including Windows MSDOS, FAT, FAT32, ExFat, and NTFS formats, but unless you intend on using the drive between a Windows and Mac machine, formatting it to be entirely Mac compatible filesystem is highly recommended, and necessary for Time Machine and to make disks bootable.

If you have never formatted a drive before on the Mac, don’t worry, it’s super easy and we’ll walk you through the entire process.

How to Format an External Drive for Mac Compatibility

This is a simple procedure and is achieved the same way for all drive types and through all connections, be they USB, Firewire, or Thunderbolt. Formatting a drive will erase all data and partitions on the disk:

  1. Connect the hard drive or USB key to the Mac
  2. Launch Disk Utility, located in Applications > Utilities
  3. Locate the drive name from the left hand side of Disk Utility and click on it
  4. Click on the “Erase” tab across the top
  5. Format a USB Flash Drive for use in Mac OS X

  6. Next to “Format:” click the contextual menu and select “Mac OS Extended (Journaled)”
  7. Format to Mac Filesystem

  8. Name the drive if you want, the name can be changed at any point
  9. Click the “Erase” button and confirm again on the next pop-up window

Format a USB Drive for use on a Mac

That’s all there is to it, the drive will now format and erase everything on it.

Smaller external hard drives, SSD’s, and USB flash keys format quickly, while a larger hard drive may take a while longer. When completed, the drive will be formatted to the Mac OS X compatible HFS+ filesystem.

The videos below demonstrate the complete process of formatting an external hard drive for full Mac OS X compatibility, this uses the new Disk Utility in modern versions of OS X:

Similarly, you can perform the same type of process in OS X for making a USB flash drive compatible with Mac OS using the Disk Utility in OS X, as you can see, it’s a quick procedure that is done in short order on any Mac:

Should you intend to make an OS X installer drive (for OS X Mavericks, OS X El Capitan, OS X Yosemite, etc) or create any other bootable Mac OS X volume from a drive, or use a new drive as a fully compatible Time Machine backup drive, you will also need to complete this process.

The process of formatting a drive to be compatible with Windows PC and Mac OS X requires a different format choice, but is otherwise quite similar.

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Posted by: Paul Horowitz in Mac OS X, Tips & Tricks


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  1. Andy Robinson says:

    Note that Windows can not read/write HFS+ so if you have any Systems running Windows or friends who you might borrow a USB stick or external HDD they will not be able to access these media if formatted to HFS+ (except if they install software like MacDrive which enables to read/write HFS+ media from Windows).

  2. Fernando says:

    I did this with a WD 1TB, but it took me 600 MB of space!!!!

  3. Emaven says:

    What if that USB drive has U3 software on it. I read that you can ruin the USB drive if you don’t do it in a special way.

  4. […] you only intend on using the drive on a Mac it’s recommended to format for Mac OS X use only using the journaled file system. Just be aware that the Mac-only formats are typically not readable […]

  5. Joe says:

    thanks man. Works great :)

  6. Sam says:

    Help – new mac user. If I want to read files, videos etc on a mac, that I loaded onto my hard drive through a pc, how can this be done?

    Appreciate your hep in advance

    • chung says:

      If you’re intent is to only read files loaded from a pc from a mac, the standard windows NTFS format should suffice. As the article mentioned, this is one of the common formats in external hard drives.

      If you want the ability to read and write in both windows and mac, format to the MS-DOS (DAT) format.

  7. Lina Alvarez says:

    Oh my gosh. Thank you. Thank you. Thank you. I have been fighting with a Click Free external drive (just plug in and it’s done!) for over a week. I have contacted customer service. I have reinstalled NTSF whatever. error. error. error. I was going to mail it back this morning. I just did what you said and it is now backing up. Keeping my fingers crossed but SO relieved! Can check this off my list and move on.

  8. sorriso says:

    OMG THANK YOU SO MUCH – so easy an quick. everything works fine.

  9. Thasleem says:

    Thank You So much dude, now i am really happy :)

  10. Debbie says:

    I have external HD and want to use it with my mac. But I have several pictures on this HD. I want to be able to add folders and continue to put several of my pictures and files on it. WHat do I need to do?

  11. Timothy says:

    Thanks man. It worked perfectly

  12. […] both Mac and Windows, are not compatible for using as a Time Machine drive, and as they are not exclusively formatted for the Mac, will have other limitations which are not desirable for exclusive Mac OS X […]

  13. Deon says:

    i have a WD portable hard drive – 500 gb
    I want to format it for my mac, but when i plug it in the USB port , the mac does not read the drive and therefore i cannot format it
    please help

  14. Noreen says:

    I have an external hard drive that used to work with my mac. Now it is reasonable only on a mac but I can read and write in a windows pc. How can i make it read and write for both mac and windows

  15. April says:

    I have an external drive and tried going to disk utilities….Erase…Mac OS extended (journaled)….Erase I get an error that it is unable to format. Any suggestions? the external drive is brand new 1TB Tuxera NTSF external hard drive.

  16. Sayna says:

    Thank you so much !!! :]

  17. susan says:

    The comment at the end is confusing (see the last phase in quotes below)…Is that just an advertisement?…it goes to a Dell site. I want to follow the 7 step instructions to format a backup drive for my 10.4.4 Yosemite Time Machine system. Can I follow the 7 steps and achieve that? and just ignore this addition instruction in quotes? “Should you intend to make an OS X installer drive (for OS X Mavericks, OS X El Capitan, OS X Yosemite, etc) or create any other bootable Mac OS X volume from a drive, or use a new drive as a fully compatible Time Machine backup drive, you will also need to complete this process.”

  18. Jared says:

    Very well written!
    Thank you so much for your help

  19. Keith says:

    I purchased a WD my passport 1 TB external hard drive through What I didn’t realize was that it wasn’t one for mac. Is it okay to keep it and reformat it for mac or am I much better off returning it and buying another one specifically for mac?

  20. phoeniss says:

    i tried to do this and it failed. it would not give me details.

  21. Zoë says:

    The same problem – trying to reformat my flash drive and I keep getting failed response – first erased free space and it came up with an error/reason it couldn’t work – the second time it said “A disk with a mount point is required.” Then I hit plain old “erase” and it tells me it “couldn’t modify partition map.” Help?

  22. Negar says:

    Thanks :P

  23. Aiman says:

    so i just did everything what it says, and now my tv cant read my usb. what should i do?

  24. AudioHTIT says:

    The Disk Utility has changed, you might want to update the screen shots to reflect the new version, the Partition tab is noticeably different.

  25. Ankush Goel says:

    I want to use the pendrive and hard drive on both OS’s so which settings should I have to use ?

  26. Nigel says:

    Just bought a 4TB Segate Drive for my Mac to use with Time Machine . . . when I try to use disk utility . . .
    Connect the hard drive or USB key to the Mac
    Launch Disk Utility, located in Applications > Utilities
    Locate the drive name from the left hand side of Disk Utility and click on it
    Click on the “Erase” tab across the top . . .
    It Fails and says: Disk Erase Failed. Couldn’t Unmount Disk . . . . what can I try to reformat this disk?

    • Bob says:

      Try a different USB port and make sure the hard drive USB is plugged directly into the Mac and not through a USB hub. For whatever reason the Mac commonly struggles with USB hubs, I think because they are not powered. I get similar errors constantly when using USB hubs on Mac with external drives, but when plugged directly into Mac the hard drives work.

      Also make sure the external drive is not locked.

      • Wayne says:

        Having the identical problem connected directly to USB on the back of iMac. Since the Disk Utility changed I have not been able to reformat Seagate drives, Western Digital are fine. How do you tell if it is locked?

  27. Janet DeLand says:

    I have a new maxone external drive, and it is not recognized in the left-hand panel of the Disk Utility. It is connected by USB cable, plugged directly into mu iMac.

  28. Ray says:

    I have an Iomega Ext. drive with files from a Windows based PC that I want to keep. The storage is half full with over 567MB of storage left. Am I able to continue with the formatting without erasing the current files that are already on it?

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