Here's how to format USB on Mac

Nowadays, when you buy a USB drive, you can use it right out of the box with your Mac. However, unless it’s been designed for use with a Mac, it won’t be formatted using macOS’ preferred file system (either Mac OS Extended or APFS, depending on which version of macOS you’re running).

That’s because most in the world run Windows, and Windows uses a different file system, usually one known as Fat32. Drives formatted as Fat32 can be read from and written to by macOS, but it’s not optimal, and you’re more likely to run into problems than if you use macOS’ native format. So, if you’ve bought a USB drive that’s formatted as Fat32 or any other format other than Mac OS Extended (also known as HFS+) or APFS, here’s how to format USB for Mac. It’s exactly the same procedure if you need to reformat a flash drive on a Mac.

How to format a USB drive on a Mac

Here are the steps for formatting flash drives on Mac:

1. Plug the drive into a USB socket (if you have a recent MacBook or MacBook Pro that only has USB-C connectors, you’ll need a USB-C to USB-A adaptor).

2. Open a new Finder window and click on the drive. Make sure it has no files on it that you need. The process of reformatting it will wipe all the data from it.

3. Once you’ve copied any files you need from the USB drive to your Mac, go to Applications > Utilities and double-click on Disk Utility.

4. Click on the USB drive in the sidebar and then choose Erase from the toolbar at the top of the window.

5. In the window that drops down, type a name for the formatted drive in the box next to Name.

6. Choose a format from the dropdown menu.

7. If you have previously stored sensitive data on the drive, click the Security Options tab. 

8. Choose a security level using the slider. The further to the right you move the slider, the more ‘passes’ the erase tool will make, and the more securely files will be deleted. However, it also increases the time it takes to format the drive quite considerably.

9. Click OK and then click Erase.

Tip

You don’t need to erase a whole drive to delete files securely. If you have confidential files or sensitive data you need to remove from your Mac completely, you should use CleanMyMac’s File Shredder. It’s specifically designed to securely delete sensitive data and will render it unrecoverable. You can download CleanMyMac X for free here.

Which format to choose?

If your Mac is running macOS High Sierra or later, you have two options for formatting thumb drive on Mac: APFS and Mac OS Extended. Which should you choose? The key point is that disks formatted as APFS won’t be recognized by Macs running versions of macOS older than High Sierra. So, if you think you might need to plug the USB drive into a Mac running an older version of macOS, format it as Mac OS Extended.

APFS is optimized for SSD (solid state drive) such as flash drives, so if you reformat a flash drive on a Mac, you should definitely choose APFS (unless you plan to use it with a pre-High Sierra Mac, of course). Even on hard drives, however, APFS is faster and more reliable than Mac OS Extended.

Finally, if you plan to use the USB drive as a destination for Time Machine backups, choose Mac OS Extended. Time Machine can’t currently back up to an APFS disk, and if you select one for use with Time Machine, it will offer to reformat it as Mac OS Extended. You can, however, backup an APFS formatted disk to a Mac OS Extended Time Machine drive.

How to format a USB drive to FAT32 on a Mac

The main reason for formatting a USB drive as Fat32 on a Mac is that you want to be able to use the drive on a Windows PC as well as a Mac — perhaps to transfer files between the two machines. You may also be preparing the drive for use as, say, a storage device for a media player or to record TV programs on a TV with a USB port.

The fact that Fat32 can be read from and written to on both Mac and Windows makes it very versatile. However, there is a significant limitation — individual files have a maximum size of 4GB. So, if you’re using the USB drive to store large video files, you may run into trouble. There is a solution, however, — exFAT. Unlike FAT32, exFAT doesn’t have a maximum file limit. Better still, it can be read from and written to on any Mac running Mac OS X Snow Leopard or later and on Windows.

To format a USB drive in FAT32 or exFAT:

1. Plug the USB drive into your Mac.
2. Go to Applications > Utilities and open Disk Utility.
3. Click on the USB drive in the sidebar in Disk Utility.
4. Click Erase in the Disk Utility toolbar.
5. Type in a name for the formatted disk.
6. Click on the Format menu and choose either MS-DOS (FAT32) or ExFAT.
7. Click Erase.

Your USB drive will now be erased and reformatted as either FAT32 or ExFAT, depending on the format you chose in step 6.

How to manage your drives easily

If you are looking for a quick and easy way to manage your drives, try using CleanMyMac’s Connected Devices tool. With its help, you can clean hidden junk from external drives and check files that take up the most space. It works for all drives, including USB drives, SSDs, SD cards, and external hard drives. All the drives will be at hand in the menu bar, so you can get to see the types of drives you have and manage them easily. It is absolutely free to download here.

Once downloaded, follow these steps to use the tool:

1. Click a little iMac icon from the menu bar. If it’s not there, open CleanMyMac X Settings > Menu and select Enable Menu.
2. Navigate to the Connected Devices tab.
3. Hover over Junk and click Clean Up to delete junk files. Alternatively, click Organize to see what takes up space on your drive.

Hopefully, now you know how to reformat USB on Mac and see how easy it is using Disk Utility. There are a couple of things you should keep in mind, however. The first is that when you format and disk, you will erase all the data currently on it. So, if you need that data, make sure you copy it onto another disk before you start. Secondly, there are several formats to choose from, each with advantages and disadvantages. Use the guide above to help you decide which is right for you.