Connect the drive and open Disk Utility
Plug your Seagate drive into your Mac using a USB cable. The drive will appear on your desktop and in Finder. Open Disk Utility — you'll find it in Applications > Utilities, or search for it with Spotlight (Command + Space, then type "Disk Utility").
In Disk Utility, you'll see your Seagate drive listed in the left sidebar. Click it once to select it. You should see the drive name, capacity, and current format listed in the main panel. Do not click into any partitions or volumes under the drive — select the drive itself at the top level.
Key Takeaways
- Formatting erases all data on the drive, so back up anything you need before you start.
- APFS is the modern format for newer Macs; Mac OS Extended (HFS+) works on older systems and with older Macs you might share the drive with.
- The erase process takes a few seconds to a few minutes depending on drive size, and the drive will be ready to use when ready after.
- If Disk Utility won't recognize the drive or shows it as unformatted, the drive may need a different approach — see the troubleshooting section.
Choose your format: APFS or Mac OS Extended
Click the Erase button at the top of Disk Utility. A dialog box will open asking you to name the drive and choose a format. The name is up to you — something like "Seagate Backup" or "External Storage" works fine.
For the format, you have two main choices. APFS (Apple File System) is the current standard and is faster on newer Macs running Big Sur or later. Mac OS Extended (also called HFS+) is older but works on any Mac and is more compatible if you plan to use the drive with older systems. If you're unsure, APFS is the right choice for any Mac from 2017 onward. The scheme should be set to GUID Partition Map — leave this as is.
Complete the erase and verify the result
Click Erase to start the process. Disk Utility will show a progress bar. The operation usually finishes in under a minute for most drives, though larger drives may take a few minutes. Do not unplug the drive during this time.
When the erase finishes, the drive will appear on your desktop with the name you chose. Open Finder and click the drive in the sidebar to confirm it's empty and ready to use. You can now copy files to it or use it for backups.
Formatting a drive that won't show up in Disk Utility
If your Seagate drive doesn't appear in Disk Utility at all, try unplugging it and plugging it into a different USB port on your Mac. Some ports deliver more power than others, and external drives sometimes need it. Wait a few seconds after plugging in — the drive may take a moment to spin up and register.
If the drive still doesn't show, try a different USB cable if you have one. Cables fail more often than drives do. If you have access to another Mac, plug the drive in there to see if it appears — this tells you whether the problem is the drive itself or your Mac's USB setup.
If the drive appears in Disk Utility but shows as "uninitialized" or "not formatted," you may need to partition it first. Click the drive, then click Partition at the top. Choose 1 partition, name it, select your format, and click explore. This creates a partition table that Disk Utility can then format normally.
Formatting a drive that's already been used on Windows
Seagate drives sold for Windows use NTFS format, which Mac can read but not write to without third-party software. If you want to use the drive for both reading and writing on your Mac, you need to reformat it. The process is the same as above — select the drive in Disk Utility and click Erase, choosing APFS or Mac OS Extended.
If you want to keep the drive compatible with both Windows and Mac computers, format it as exFAT instead. In the Erase dialog, click the Format dropdown and select exFAT. This format works on both systems, though it's slower than APFS and has a 4 GB file size limit per file.
What to do if Disk Utility shows an error during formatting
Common errors include "the disk could not be unmounted" or "the operation could not be completed." These usually mean something is still using the drive. Close Finder windows showing the drive, quit any backup software (like Time Machine or Carbon Copy Cloner), and try again.
If you see a permissions error, restart your Mac and try the format again when ready after restart, before opening other applications. If the error persists, the drive itself may have a hardware problem — try connecting it to another Mac to see if the error repeats. If it does, the drive may need service or replacement.
Frequently Asked Questions
Will formatting erase everything on the drive?
Yes. Formatting erases all data on the drive. Before you format, make sure you've backed up anything you need. Once you click Erase in Disk Utility, the data is gone and cannot be recovered through normal means.
Can I format a Seagate drive that's currently my Time Machine backup?
You can, but Time Machine will stop backing up until you set it up again. Go to System Preferences > Time Machine, turn off Time Machine, unplug the drive, format it, plug it back in, then open Time Machine and select the drive again. Time Machine will start fresh with a new backup.
What's the difference between APFS and Mac OS Extended?
APFS is newer and faster on modern Macs. Mac OS Extended works on older Macs and is more compatible if you share the drive with systems running older versions of macOS. If your Mac is from 2017 or newer, use APFS. If you need to use the drive on older Macs, use Mac OS Extended.
Do I need to do anything special for a Seagate drive versus another brand?
No. Seagate external drives format the same way as any other brand in Disk Utility. The process is identical whether the drive is Seagate, Western Digital, Samsung, or any other manufacturer.
Can I partition the drive into multiple sections?
Yes. In Disk Utility, select the drive and click Partition. You can create multiple partitions with different names and formats. Each partition will appear as a separate drive on your desktop. Most people don't need partitions — a single partition is simpler and uses the full capacity.