Formatting on a Mac computer. How do I format my device using a Mac computer? WARNING: Formatting will erase all data on the device. Back up all your data before proceeding. Instructions below are for 10.11.x (El Capitan) and 10.12.x (Sierra). Formatting a memory card, flash drive or device using a PC.
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Hello and welcome to my User Tip.
I will explain to you just the basics how storage drives operate in regards to different operating systems, formatting and partitions, especially sharing data with Windows PC's which is the most common asked about issue.
For simplicity sake, I have stuck to the most current used formats and steps on Mac's and PC's that your likely to encounter and encouraged to use now.
Remember to always: 'Safely remove hardware' before physically disconnecting from a PC
and also to drag the drive to the Trash Can/Eject before physically disconnecting on the Mac.
Quick format methods
Whenever you changing the drive, there is the potential for the lost of data.
So make sure you have a copy of the data off the drive your attempting to change and physically disconnect all other non-essential drives so no mistakes occur.
#1 If you want to format a drive, USB Thumb drive etc., to only work with a recent Mac and to boot OS X with
Open Disk Utility and select the drive makers name and size on the far left, then Partition: Options: GUID partition table and Format: OS X Extended (Journaled) name it and click Apply.
#2 Format a drive, USB thumb drive etc., to work with Mac or a PC, on a PC. (most compatibility)
Take it to the oldest Windows PC your going to share data with, usually XP, right click on it's icon and select format:
exFAT - for large video/movie files use +4GB (pre-10.6.5 Mac's can't read this format, use FAT32)
FAT(32) - for most anything, small use (under 4GB sized files), thumb drives, most compatibility with connecting to TV's consoles and other devices
If your Windows XP machine doesn't have exFAT, there is a free download from Microsoft.
#3 Format a drive or USB thumb drive etc., to work with Mac or PC, on a Mac (most compatibility)
Take the drive to the oldest OS X version on the Mac(s), Open Disk Utility and select the drive makers name and size on the far left, then
Partition: Options: MBR partition table
Format: MSDOS (FAT32) - for under 4GB files and to work work with consoles, devices that need firmware etc., or
(Format: exFAT - for over 4GB sized files (Mac's pre OS X 10.6.5 won't have exFAT))
Note: Reports of issues that exFAT formatting on a Mac doesn't work well with Windows PC's, use the oldest Windows version instead.
#4 Format a drive or USB thumb drive etc., to work with only between recent Mac 10.6.5+ & Vista-Win 7, on a Mac
Open Disk Utility and select the drive makers name and size on the far left, then
Partition: Options: GUID partition table
Format: MSDOS (FAT32) for under 4GB sized files, or
Format: exFAT - for +4GB sized files (exFAT is proprietary, patent pending, may have to pay later)
Note: Reports of issues that exFAT formatting on a Mac doesn't work well with Windows PC's, use the oldest Windows version instead.
More in depth explanation
Partition Map or Table - is instructions written at the beginning of the drive that tell the hardware it's running from: what, how many, and where the partitions are on the drive. There is only one partition map on the drive. It can be MBR or GUID.
Partition - is a space on the drive that appears as another volume, but still resides on the same piece of physical hardware.
Formatting - is how a entire drive or partition is structured to hold data, one drive can be partitioned into many separate partitions each with their own formatting. The Partition Map holds all the information of what is what.
Changing the partition map/table scheme will erase all data on the entire drive, it's like burning a treasure map, no directions anymore.
Format For Mac And Pc External Hard Drive![]()
Changing the format of a single partition on a multi-partitioned drive only erases the data on the partition being formatted.
Questions
How do I format a entire external drive on a Windows PC?
Open the file manager and locate the drive (empty of data, or data you wish to delete) and right click on it and 'format' and choose a format, Windows will create the MBR or GUID automatically if there is none depending upon what version of Windows your using.
It's best to format on the oldest PC being used as the future versions of Windows (and Mac's) can read the older formats.
I have a drive from a Windows PC, the Mac can/not read or not write to it. What do I do?
It's likely formatted NTFS by Windows, it's best to take it back to the Windows machine, remove the data and reformat it FAT32 or exFAT, then place the data back on. (please read further on about the differences between FAT and exFAT)
Recent Mac's can read NTFS, but not write to it, so this might be enough to transfer data off, then reformat the drive. Check the data was transferred and is accurate before changing the drive format and thus erasing it.
There is third party software than can be installed enable read/write of the NTFS format on Mac's, you'll need to search online for it. It's hassle, you'll have to pay and have it updated like any other software. A neutral exFAT or FAT32 (MSDOS) format is better as either platform can read it without more software installed.
How do I format a entire external drive on a Mac?
Unmount and disconnect all other drives to prevent a mistake. Open Disk Utility in the Applications/Utilities folder and select the drive on the far left with a makers name and size, then click Partition tab: Options: (for a establishing a specific partition map scheme), partitions, and Format (for selecting a specific format for the drive/partitions)
How do I format a drive for booting with a Mac?
Same steps as above, choose GUID as the Partition map under Options, and OS X Extended journaled (HFS+) as the format for the partition your going to be installing OS X into. Windows needs MacDrive to access this Apple HFS+ drive format.
There is no choice for MSDOS format on the PC, or FAT32 on the Mac, what do I choose?
FAT32, if it just says FAT, it usually means FAT32 (as FAT16 is on the way out.). MSDOS is what Apple calls FAT32.
I formatted the external drive exFAT or FAT32 (MSDOS) on my Mac and took it to a PC and it asks me to format!
Don't format it (unless your willing to erase all the data on it)
Format Flash Drive For Mac And Pc
Take the drive back to the Mac and copy off the data (if you don't have a copy on the Mac already) and try formatting it again, this time making sure to select the Option: MBR then chose the format. (exFAT or MSDOS) and click apply.
If it still doesn't work, format the drive on the PC.
OS X appears to be using too big of a block size. It's technically correct, but Windows doesn't like it when the block size is larger than 1024 KB. Formatting on Windows creates the disk/flash drive with a smaller block size that both system like. Unfortunately, OS X doesn't give you an option to pick a block size. It just uses a default in relation to the size of the drive being formatted.
I went to format a Bootcamp / second partition on my boot drive and it's restricting my size, I know I have more free space available
Your partitions are stacked like so before creating the second partition.
EFI (hidden)
OS X - say 100GB
10.7+ Recovery HD (if on 10.7+, hidden)
Your partitions are stacked like so after creating the second partition.
Formatting Passport For Mac And Pc
EFI (hidden)
OS X - 50GB
Bootcamp / Second Partition - 50GB
10.7+ Recovery HD (if on 10.7+, hidden)
When you try to create a Bootcamp / Second partition it's started from the bottom free space remaining on the OS X Partition and works it's way up until it hits data written on the drive from OS X. If that partition size is too small to install Windows, then Bootcamp will say it can't continue.
Hard drives write data on a drive from the top down where it can find space. When files are deleted it leaves holes and thus the data on the drive isn't all nice and compact all the time to provide all the free space at the bottom of the drive to create the second partition.
To fix this requires cloning one's OS X partition to a external drive, hold option boot from it to check it out, erase the OS X partition in Disk Utility (booted on the clone) onto the internal drive OS X partition, then reverse clone the external OS X partition back onto the internal OS X partition.
This will effectively write all the data of the OS X partition starting from the top of the partition and working downward, so when you boot off the internal OS X partition you will be able to format your second partition with more of your remaining free space available.
Read more about clone/reverse clone here:
Mac Formatting Tool
Can I have more partitions on my boot/external drive?
With OS X, your allowed to create one more partition using Bootcamp on the boot drive. It's formatted FAT32(MSDOS) which if you go and install Windows 7 via their install methods will change that format to NTFS. (have to change the format as Windows only installs into NTFS)
You can create/delete one more partition using Disk Utility or Bootcamp on the boot drive and then use Disk Utility to change to another format for that partition, but DU won't format NTFS. You really only get one more partition on the boot drive, if it's used up for Bootcamp that's it.
You can use Disk Utility to change the format of the Bootcamp partition to GUID and OS X Extended Journaled and install OS X there, or clone it from the first partition even.
Technically it's possible to have up to 16 partitions on a external drive, but the OS X internal boot drive is mostly limited to one extra.
Use a blank external drive, Disk Utility and experiment applying Partition Map schemes, creating partitions and formatting those partitions.
Creating/deleting a partition on a booted system can be risky, always have a copy of your personal user data files off the machine before proceeding.
Bootcamp or Disk Utility hangs or won't format
If you have a problem formatting your second partition in Disk Utility or Bootcamp, quit Bootcamp, hold c and boot from the 10.6 disks, or hold command r keys and boot (wired or built-in keyboard required) into RecoveryHD and use Disk Utiltiy to Repair the drive twice.
Then reboot normally use Disk Utility >Erase Free Space > Zero first on the OS X partition, let it work, takes a while and then try creating your Bootcamp or Disk Utility partition again.
If you have a problem formatting your external drive, or any partition on that drive, don't care about the data there, then use Disk Utility >Erase > Zero either that whole drive, or the partition (be careful what you choose!) then try formatting again. Zero Erase the entire partition or drive removes all data on it.
Also there is a issue with BootCamp that there is files where it needs to go on hard drives.
What's the difference in Disk Utility between the entire drive/media, and partitions?
The entire media will have the size and the makers name on the left, the partitions on it are indented underneath.
When one selects their entire drive media, they are affecting change to all partitions on the drive, hidden included.
Note: In 10.7+ selecting the entire drive likely is only possible via a external boot drive/disk/USB (or via Firewire Target Disk Mode w/another Mac)
Note: 10.6 doesn't have a Recovery Partition like 10.7+ has, if it was it would be the last partition on the media.
This graphic shows a 10.6 internal drive with the secondary partition and the hidden EFI partition made visible, you won't see this normally.
So, you just bought an external hard drive or a portable SSD and wanted to use it on your Mac. But somehow, macOS doesn’t allow you to write data to the drive.
That’s all because it’s been initialized with Windows NT File System (NTFS), which is primarily for PCs. Apple Mac machines support a different file system.
In this post, I’m going to show you how to format your external drive for a Mac compatible file system i.e. Mac OS Extended (Journaled). Just follow this easy step-by-step guide and you’re all set.
Important note: If you have useful files stored on the external drive, be sure to copy or transfer them to another safe place prior to formatting. The operation will erase all data and your files will be gone for good. You could use a recovery program like Data Rescue to retrieve them, but the odds of recovery vary.
Pro tip: If your external drive has a large volume, like mine – a 2TB Seagate Expansion. I highly recommend you also create multiple partitions. I’ll also show you how to do that below.
Most External Hard Drives Are Initiated with NTFS
During the last several years, I’ve used several removable drives, including a 500GB WD My Passport, 32GB Lexar flash drive, and a few others.
Three weeks ago, I bought a brand new 2TB Seagate Expansion to backup my MacBook Pro before I updated to the latest macOS, 10.13 High Sierra (also see those High Sierra issues I encountered).
When I connected the Seagate to my Mac, the drive icon showed up like this.
When I opened it, the default content was all there. Since I wanted to use it on Mac, I clicked the blue logo with the text “Start_Here-Mac”.
It brought me to a webpage on Seagate’s site, where it clearly indicated the drive was initially set up to work with a Windows PC. If I wanted to use it with Mac OS or Time Machine backup (which is my intent), I’ll need to format the drive for my Mac.
I then right-clicked the external drive icon on Mac desktop > Get Info. It showed this format:
Format: Windows NT File System (NTFS)
What is NTFS? I’m not going to explain here; you can read more on Wikipedia. The problem is that on macOS, you can’t work with files saved on an NTFS drive unless you use a paid app Paragon NTFS for Mac.
How to Format an External Drive to Work with Mac (from NTFS to Mac OS Extended)?
Note: The tutorial and screenshots below are based on macOS Sierra 10.12.5. They might be different if your Mac has a different version.
Step 1: Open Disk Utility.
The quickest way to do this is a simple Spotlight search (click the search icon on the upper right corner), or go to Applications > Utilities > Disk Utility.
Step 2: Highlight your external drive and click “Erase”.
Make sure your drive is connected. It should show up on the left panel under “External”. Select that disk and click the “Erase” button, the one highlighted in red in the screenshot below.
Step 3: Select “Mac OS Extended (Journaled)” in Format.
A new window will pop up asking which file system you’d like to format the external drive to. By default, it’s the Windows NT File System (NTFS). Select the one shown below.
Pro tip: If you want to use the external drive for both Mac and PC, you can also select “ExFAT”. Learn more about the differences between these file systems from this thread.
By the way, you can also rename your external drive.
Step 4: Wait until the erasing process is complete.
For me, it took less than a minute to format my 2TB Seagate Expansion.
You can also check to see if the format was successful. Right-click on the icon for your external drive on Mac desktop, then select “Get Info”. Under “Format”, you should see text like this:
Congratulations! Now your external drive has been formatted to be fully compatible with Apple MacOS, and you can edit, read, and write files to it as you want.
How to Partition an External Hard Drive on Mac
If you want to create multiple partitions on your external hard drive (in fact, you should for better file organization), here’s a step-by-step guide:
Step 1: Highlight your drive and click “Partition” in Disk Utility.
Open the Disk Utility app and highlight your external hard drive. Make sure you select the disk icon right under “External”. If you select the one below it, the Partition option will be greyed out and become unclickable.
Step 2: Add partitions and allocate volume for each one.
After clicking “Partition”, you’ll see this window. Located on the left is a big blue circle with the name of your external drive together with its volume size. What you need to do next is click the add “+” button to increase the number of partitions on your external disk. Then allocate the desired volume to each partition. You can do that by clicking the small white circle and dragging it around.
After that, you can rename each partition and define a file system for it.
Step 3: Confirm your operation.
Once you hit “Apply”, a new window pops up asking for your confirmation. Take a few seconds to read the text description to make sure it reflects what you intend to do, then click the “Partition” button to continue.
Step 4: Wait until it says “Operation successful.”
To check whether the operation is really successful, go to your Mac desktop. You should see multiple disk icons show up. I chose to create two partitions on my Seagate Expansion — one for backup, the other for personal use. You can find more info in this post: How to Backup Mac to an External Hard Drive.
That wraps up this tutorial article. I hope you find it helpful. As always, let me know if you have any issues during the formatting or partitioning process.
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