The Two Ways to Format a Drive on Mac
You can format a drive on Mac using either Disk Utility (the built-in tool) or Terminal (the command-line interface). Disk Utility is the method most people use—it has a visual interface and takes about five minutes. Terminal is faster if you're comfortable with typed commands, but Disk Utility is safer because you can see exactly what you're doing before you commit.
Before you start, understand that formatting erases everything on the drive. There is no undo. If the drive contains files you need, back them up first or stop here. Once you format, recovery is possible but difficult and often requires professional help.
The drive must be connected to your Mac—either plugged in via USB, Thunderbolt, or already installed internally. Your Mac must be able to see it in Finder or Disk Utility for either method to work.
Key Takeaways
- Disk Utility is the safest method for most people because you can verify the drive and format type before erasing.
- You must back up any files on the drive before formatting, because the process erases everything permanently.
- Choose APFS for modern Macs (2017 and newer) or Mac OS Extended for older systems, unless you need the drive to work with Windows computers.
- The drive must appear in Disk Utility before you can format it; if it does not, check the cable connection or restart your Mac.
- Formatting takes a few minutes for most drives, and your Mac will not be usable during the process on the startup drive.
Formatting a Drive Using Disk Utility
Open Disk Utility by pressing Command + Space, typing "Disk Utility", and pressing Enter. The process opens with a list of all connected drives and volumes on the left side. Find the drive you want to format in this list. If you do not see it, the drive is not connected properly or your Mac cannot detect it—check the cable and try again.
Click the drive name once to select it. Look at the top of the window for the Erase button. Click it. A dialog box appears asking for a name, format, and scheme. The name is what the drive will be called in Finder—you can use any name you want. Do not leave it blank.
For the format, choose one of these: APFS if your Mac runs macOS 10.13 or newer (most modern Macs), or Mac OS Extended (Journaled) if your Mac is older. If you need the drive to work with Windows computers, choose ExFAT instead—both Mac and Windows can read and write to ExFAT drives. The scheme should be GUID Partition Map for most situations.
Review your choices. The name, format, and scheme are all correct. Click Erase. Disk Utility will format the drive. This takes a few seconds to a few minutes depending on the drive size. When it finishes, the drive appears in Finder with the name you chose, and it is ready to use.
Formatting a Drive Using Terminal
Terminal is faster if you know the exact drive identifier, but it is also easier to make a mistake. Open Terminal by pressing Command + Space, typing "Terminal", and pressing Enter. Type the command diskutil list and press Enter. This shows all drives connected to your Mac with their identifiers (like disk2 or disk3).
Find your drive in the list by size or name. Note its identifier—for example, disk2. Type this command, replacing disk2 with your actual identifier and MyDrive with the name you want:
diskutil secureErase freespace 0 -secureErase 0 APFS MyDrive disk2
Press Enter. Terminal will ask you to confirm by typing the drive name. Type it exactly as shown and press Enter. The drive formats. This method is more thorough because it also securely erases free space, but it takes longer—sometimes 10 to 30 minutes for larger drives. Do not unplug the drive or close Terminal while it is running.
When the command finishes, Terminal shows a message confirming the format. The drive is now ready to use.
What to Do If the Drive Does Not Appear in Disk Utility
If you connect a drive and it does not show up in Disk Utility, the problem is usually the cable, the port, or the drive itself. Try a different USB port on your Mac first—some ports are faster or more reliable than others. If you are using a USB hub, plug the drive directly into your Mac instead.
Restart your Mac. Sometimes a drive connected before startup does not appear until you restart. Shut down completely, wait 10 seconds, and turn it back on. When your Mac finishes starting, check Disk Utility again.
If the drive still does not appear, try a different cable if you have one. The cable may be damaged even if it looks fine. If you have access to another Mac, try the drive on that computer to determine whether the problem is your Mac or the drive itself.
If the drive appears in Disk Utility but shows as "unmounted" or "not mounted", click it once and look for a Mount button at the top of the window. Click it. The drive should then appear in Finder and be ready to format.
Choosing the Right Format for Your Situation
APFS is the current standard for Mac drives. It is faster, more reliable, and handles large files better than older formats. Use APFS unless you have a specific reason not to. Your Mac must run macOS 10.13 or newer to use APFS.
Mac OS Extended (Journaled) is the older Mac format. Use it only if your Mac runs an older version of macOS or if you need the drive to work with very old Macs. Modern Macs can read and write to Mac OS Extended drives, but the performance is slower than APFS.
ExFAT works on both Mac and Windows computers. Use ExFAT if you plan to move the drive between a Mac and a Windows PC, or if you need to share it with Windows users. ExFAT is slower than APFS and less reliable for very large files, but it is the only format that works seamlessly on both operating systems.
FAT32 is an older format that also works on Windows, but it cannot handle files larger than 4 GB. Do not use FAT32 unless you have an old device that requires it.
Formatting Your Mac's Startup Drive
If you want to format the drive your Mac boots from (the startup drive), the process is different because your Mac cannot erase the drive it is currently running on. You have two options: erase it using macOS Recovery, or connect it to another Mac and format it there.
To use macOS Recovery, restart your Mac and hold Command + R while it starts up. When the Recovery menu appears, click Disk Utility. You can now format your startup drive because your Mac is running from Recovery instead of the main drive. After formatting, you will need to reinstall macOS. This process takes 30 minutes to an hour depending on your internet speed.
The easier method is to connect your Mac's drive to another Mac using a Thunderbolt or USB cable in target disk mode. Restart your Mac while holding the T key. It appears as an external drive on the other Mac, and you can format it using Disk Utility normally. After formatting, reconnect it to your original Mac and reinstall macOS.
Troubleshooting Format Errors
If Disk Utility shows an error when you try to format, the drive may have a hardware problem or a file system issue. Try restarting your Mac and attempting the format again—sometimes a temporary glitch prevents the operation.
If the error persists, try formatting with a different format type. For example, if APFS fails, try Mac OS Extended instead. If that also fails, the drive likely has a hardware problem and may need replacement.
If you see an error about permissions, make sure you are logged in as an administrator on your Mac. Click the Apple menu, then System Settings (or System Preferences on older Macs), and check your user account. If you are not an administrator, you cannot format drives.
If the drive is very old or has been used heavily, it may have bad sectors that prevent formatting. In this case, the drive is failing and should be replaced. Do not continue trying to format it, as this can make the problem worse.
Frequently Asked Questions
Can I recover files after formatting a drive?
Yes, but only if you have not written new data to the drive since formatting. Recovery software can sometimes restore files from a formatted drive, but success is not may provide. The longer you wait and the more you use the drive after formatting, the lower the chance of recovery. If you need files from a drive, do not format it—take it to a data recovery service first.
What is the difference between erasing and formatting?
On a Mac, these terms mean the same thing. Erasing removes all data and prepares the drive for use. Formatting sets up the file system (APFS, Mac OS Extended, etc.) that the Mac uses to organize files. When you erase a drive in Disk Utility, you are also formatting it with the file system you choose.
How long does formatting take?
Most drives format in a few seconds to a few minutes. Very large drives (4 TB or more) may take 10 to 30 minutes, especially if you use Terminal's find erase option. Do not unplug the drive or restart your Mac while formatting is in progress.
Do I need to format a new external drive before using it?
Not always. Many new drives come pre-formatted and ready to use. However, if the drive came formatted for Windows (NTFS or FAT32), you may want to reformat it to APFS or ExFAT for better performance on Mac. Check what format it is in Disk Utility first.
What happens if I format the wrong drive?
The wrong drive is erased permanently. This is why you should always verify the drive name and size in Disk Utility before clicking Erase. If you realize you formatted the wrong drive when ready, do not use it or write anything to it—take it to a data recovery service right away. The longer you wait, the harder recovery becomes.