How to Format a USB Drive on a Mac

What formatting a USB drive means and why you might need to do it

Formatting a USB drive erases everything on it and prepares it to work with your Mac. When you format, you're telling the drive how to organize files — think of it like deciding whether shelves in a cabinet will hold books spine-out or stacked flat. The drive itself doesn't change, but the way your Mac reads and writes to it does.

You might format a USB drive because you want to reuse an old one, because it's not showing up on your Mac properly, or because you're moving it between a Mac and a Windows computer and need a format both can read. Formatting also clears out any corrupted files that might be slowing the drive down.

Before you format, understand that formatting erases the entire drive. If there's anything on it you need, copy it to your Mac first — once you format, that data is gone.

Key Takeaways

Connect your USB drive to your Mac, then open Disk Utility from Applications > Utilities.
Select your USB drive in the left sidebar, click Erase, and choose a format: APFS or Mac OS Extended for Mac-only use, or ExFAT if you need to use the drive on Windows computers too.
Name your drive something you'll recognize, then click Erase to complete the process — this takes less than a minute.
If your drive doesn't appear in Disk Utility, try a different USB port or restart your Mac before trying again.

How to open Disk Utility and find your USB drive

Plug your USB drive into any USB port on your Mac. Wait a few seconds for the Mac to recognize it — you'll usually see it appear on your desktop as an icon.

Open Disk Utility by clicking the Finder icon in your dock, then clicking Applications in the sidebar. Double-click the Utilities folder, then double-click Disk Utility. The program opens in a new window showing all the drives connected to your Mac.

Look in the left sidebar for your USB drive — it will be listed below your main hard drive. USB drives usually have a name like "Kingston" or "SanDisk" or whatever brand they are, or they might just say "Untitled" if they've never been formatted. Click on it once to select it.

Choosing the right format for your needs

Once you've selected your USB drive, click the Erase button at the top of the Disk Utility window. A dialog box will appear asking you to name the drive and choose a format.

For a drive you'll use only with Macs, choose APFS (Apple File System) if your Mac runs macOS 10.13 or newer, or Mac OS Extended if it's older. APFS is faster and more reliable on modern Macs.

If you need to use the same USB drive on both a Mac and a Windows computer, choose ExFAT. Both operating systems can read and write to ExFAT drives without any extra software. This is the safest choice if you're not sure where the drive will be used.

Do not choose NTFS (Windows format) unless you have specific software installed on your Mac to write to NTFS drives — Macs can read NTFS but cannot write to it without extra tools.

Naming your drive and completing the format

In the same dialog box where you chose the format, you'll see a field labeled "Name". Type a name for your drive — something short and clear like "Backup" or "Work Files" or "Shared Drive". Avoid special characters like slashes or colons, which can cause problems.

Double-check that you've selected the correct drive in the sidebar — formatting erases the entire drive, and you want to make sure you're erasing the USB drive and not your main hard drive by accident. Look at the size shown in Disk Utility; your USB drive will be much smaller than your Mac's main drive.

Click the Erase button in the dialog box. Disk Utility will ask you to confirm. Click Erase again. The process usually takes less than a minute. When it's done, your USB drive will appear on your desktop with the new name you gave it, and it's ready to use.

What to do if your USB drive doesn't show up in Disk Utility

If you plug in your USB drive and it doesn't appear in Disk Utility or on your desktop, try these steps in order.

First, try a different USB port on your Mac. Some ports can be finicky, and moving the drive to another port often solves the problem. Wait a few seconds after plugging it in — sometimes the Mac takes a moment to recognize the drive.

If that doesn't work, unplug the drive, restart your Mac, and plug it back in after the Mac has fully restarted. A restart can clear out temporary issues that prevent the Mac from seeing the drive.

If the drive still doesn't appear, the drive itself may be damaged or failing. Try plugging it into a Windows computer or another Mac if you have access to one — if it doesn't show up there either, the drive may need to be replaced.

Fixing a drive that won't erase or shows an error

Occasionally a USB drive will appear in Disk Utility but won't erase, or it shows an error message when you try. This usually means the drive has a problem that Disk Utility can't fix automatically.

Try this: select the drive in Disk Utility, click the First Aid button at the top, and let it run. First Aid scans the drive for problems and fixes what it can. Once First Aid finishes, try erasing the drive again.

If First Aid doesn't help and the drive still won't erase, the drive may be physically damaged or may have firmware issues that require specialized tools. At that point, the drive is usually not worth repairing — USB drives are inexpensive enough that replacing it is the practical choice.

Frequently Asked Questions

Can I format a USB drive while files are still on it?

Yes, but formatting will erase those files. Copy anything you need to your Mac first, then format the drive. Once you click Erase, the files are gone and cannot be recovered through normal means.

What's the difference between APFS and Mac OS Extended?

APFS is newer and faster on modern Macs. Mac OS Extended is older but still works fine. If your Mac runs macOS 10.13 or newer, use APFS. If it's older, use Mac OS Extended. Both work only with Macs.

Will formatting a USB drive make it faster?

Formatting clears out clutter and corrupted files, which can help an old drive run better. But the drive's actual speed is determined by its hardware. A slow drive will still be slow after formatting, just with a clean slate.

Can I use ExFAT on a very old Mac?

ExFAT works on Macs running macOS 10.6.8 and newer, which covers almost all Macs still in use. If your Mac is older than that, use Mac OS Extended instead, though you won't be able to use the drive on Windows computers.

What happens if I unplug the drive while it's formatting?

Don't do this — unplugging during formatting can damage the drive or leave it in an unusable state. Let the format complete, which takes less than a minute. If you accidentally unplug it, plug it back in and try formatting again.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.