How to format an external drive on a Mac

2 min read · 5 steps · Updated 2 October 2026

A new drive, or one used with Windows before, often needs formatting before a Mac can write to it. The right format depends on where you will use the drive.

The pictures are diagrams of the keys to press.

Step by step

1. Copy off anything you need

   Erasing removes every file on the drive, and it cannot be undone.

   Done

2. Open Disk Utility

   Press Command + Space, type Disk Utility and press Return.

   Done

3. Show all devices and select the drive

   Choose View, Show All Devices. In the sidebar, click the top entry for the external drive, the one with the maker's name, not the volume indented beneath it.

   Done

4. Click Erase and choose a format

   APFS is best for a drive used only with Macs. ExFAT works on both Mac and Windows and with most TVs and cameras. Mac OS Extended (Journaled) suits older Macs. Leave Scheme on GUID Partition Map.

   Done

5. Name the drive and click Erase

   It takes from a few seconds to a few minutes. Click Done.

   Done

Good to know

Check twice that you selected the external drive and not the Mac's internal disk.

Always eject a drive before unplugging it: click the eject icon next to its name in Finder. This matters most with ExFAT, which is easier to corrupt.

macOS can read drives formatted as NTFS, the usual Windows format, but cannot write to them.

For Time Machine backups, let Time Machine format the drive itself: how to back up a Mac with Time Machine.

In short: Disk Utility, View, Show All Devices, select the drive, Erase, choose format.