Note, for hard drive model specific issues, see this tip:
For data recover issues, see this tip:
Mac OS 10.13, released September 25, 2017 has introduced a new file system, APFS:
discusses using Disk Utility for the new file system.
Note: when an SSD, or other solid state media (such as a USB stick or SD card) is used to install Mac OS 10.13 High Sierra or Mac OS 10.14 Mojave, it automatically chooses APFS. The side effect of this is that any older system than High Sierra, can't read the drive directly, unless it used shared via a networking protocol such as FTP. Mounting it via USB while booted off an older system renders the drive invisible. There is a way at least to bypass this automatic formatting in High Sierra:
/Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO
A command which is issued in the Terminal. Not for the faint at heart, but worth a try if you have a spare drive to test it on.
Partitioning lets you specify the format of a drive when partitioning.
If you have an Intel Mac, you can see the end of this tip about several methods of partitioning.
For backup solutions, see this tip:
These common formatting options exist for hard drives and flash drives, which you may see, and are usable in the manner suggested:
1. ExFAT for non-Mac bootable but Mac OS X 10.6.5 or later read/write hard drives that can boot XP SP 2 or higher. For more on upgrading to 10.6.5 or later, see this tip.
2. FAT32 for non-Mac bootable, but any Mac OS read/writable 4 GB and under drives you can use with any version of Windows to boot Windows.
3. NTFS for non-Mac bootable, but any Mac OS read-only without third party software larger hard drives you can use with any version of Windows to boot Windows. Tuxera NTFS, Google's Macfuse, and Paragon Software NTFS-Mac are three options for making it writable by Macs.
Some versions of Mac OS X offer NTFS support if you want to fiddle with superuser command line routines. If you are comfortable with such routines, and have a backup in case something goes wrong, I did find these routines, which I have not tested:
4. HFS+/GUID to boot Intel Macs, but not boot Windows, and not be readable by PowerPC Macs (pre-2006 601, 603, 604, G3, G4, G5). Macdrive needed to read from Windows without a network. Note: Western Digital has noted some of their hard drives can't boot Intel Macs no matter what the formatting:
http://wdc.custhelp.com/app/answers/detail/a_id/1787/ GUID Macs support no erase partitioning, which still is only recommended with backing up.
See the end of this tip for methods of partitioning.
5. HFS+/Apple Partition Map /Journaled to boot PowerPC Macs with Mac OS X 10.2.3 or later if the Mac is older than the operating system, but not Windows. Macdrive needed to read from Windows without a network.
6. HFS+/Apple Partition Map/not Journaled to boot any PowerPC Mac with Mac OS 8.1 or later if the Mac is older than the operating system, but not Windows. Macdrive needed to read from Windows without a network.
Note: for 5 & 6, there is limited support for above 128GB partitions on this article:
Also Mac OS 9 formatting is needed for older boot of Mac OS 9, as is described here if formatting from Mac OS X on a Mac that can boot Mac OS 9:
External drives may not be affected depending on how the bridge for the external drive was programmed.
7. HFS Standard to boot Mac OS 8.0 or earlier Macs. Macdrive needed to read from Windows without a network.
You are only likely to run into 1 through 4 today.
Very rarely will 5 - 7 appear.
Notes: 4k Hard drives have been supported since Mac OS X 10.4 according to: http://knowledge.seagate.com/articles/en_US/FAQ/221411en?language=en_US
SATA bus speeds that are higher than your computer's built in SATA bus may require a jumper to downstep to your computer's speed. A firmware update
addresses the issue for some MacBook Pros:
Only the 17" MacBook Pro, and Unibody model MacBooks support the 12.5mm height drives. The rest require 9.5mm height drives.
For CDs and DVDs, you are likely to run into
1. The wrong thickness, size or shape.
2. Joliet and UDF which is supported by (defunct as of 2012) Software Architect's ReadDVD (available for 10.4 and 10.5 PowerPC and Intel) in situations where the Mac operating system can't handle it directly. Unknown if it works with 10.6 Intel or later.
There is also Taffysoft's UDF Media Reader, which is available for 10.4 & 10.5 PowerPC, and 10.7 Intel and later, and has been tested on 10.9 in this forum. It is unknown if it works with 10.6 and together with VLC can read Video_TS files for playback.
4 Formatted specifically for Mac files, which can't be read by Windows.
Make sure you understand the data utilities you use and how they format or partition the discs in question to ensure your drive or disc is able to be used in the environment you desire. Many of the Windows formatting solutions here work better when Windows is installed on a Mac.
5 To date, no Mac has been built with Bluray support built-in. See this tip if you wish to use Bluray.
6 Standard movie DVDs can open with Apple's DVD Player. Extras that are playable on a computer as an application either need InterActual's DVD Player, or to run Windows as is stated in item 3 above. http://www.videolan.org/ has a VLC video player that also can read some movie DVDs Apple's software can not.
For both if the PRAM battery is over 4 years old, external devices and optical discs may start failing to work even before the system clock doesn't work properly anymore. Not all Macs have a PRAM battery, some have a PRAM capacitor. Check with Apple support which your Mac has.
Apple's articles on partitioning that can help you with formatting hard drives according to some of the formats above, depending on the version of Disk Utility, or installed operating system that came with Disk Utility: