How to Format USB or SSD on Mac

You have plugged a storage medium (USB drive, external disk, memory card) on your Mac, but you can’t save any file ? After a proper formatting, you can use it as you wish.

Nothing is more simple today than plugging a USB drive, an external disk or a memory card into a computer to retrieve files that are on it or to copy new ones. Except that exchanges between the macOS and Windows worlds are not always smooth, especially because of the file system used by default on both OS.

Thus, when you plug a USB drive from a PC into a Mac, it is not uncommon to have a bad surprise. The drive is displayed in macOS, you can see its content and copy it to the Mac. This is because macOS knows how to read the NTFS (New technology file system) file system, so dear to Windows. On the other hand, it does not know how to manage it in writing, to save files. Fortunately, there are file systems common to both OS such as FAT32 or ExFat that can be chosen at will when formatting the USB drive or any other storage medium such as a hard disk, SSD or memory card. To know how to proceed on a PC, read our practical sheet Formatting a disk, a USB key or a memory card with Windows.

Here is how to format your USB flash drive with macOS. The method is the same with an external disk or a memory card.

  • Insert the USB in one of the USB ports of your Mac. If necessary, recover the files stored on it by copying them to the Mac’s disk. They will be deleted from the flash drive during formatting. Next, launch the Disk Utility software that comes with the system. It can be found in the Applications folder, macOS Utilities.
  • In the window that appears, select your USB flash drive in the left pane. It will appear under External.
  • Click the Delete button at the top of the window. A dialog box appears.
  • If you wish, give your USB flash drive a name. Then pull down the Format menu and choose the desired format. If the key is intended only for the Mac world, choose Mac OS extended (journaled). Be careful, it will not be readable with a Windows PC. If, on the contrary, you want to use it between Windows and MacOS, choose MS-DOS (FAT) or ExFAT. Be careful, in these last cases, the writing times (the copy) from a Mac will be longer.
  • Finally, click on Delete. The formatting process begins. The USB is first "unmounted" from the system – it no longer appears on the Desktop or in a Finder window -, then reset according to the chosen format. The data it contains is deleted in the process. The key is then "reassembled" in the system to appear again in the Finder.
  • A summary of the operations performed is displayed. Click on OK.
  • Your USB drive is ready to use.

Nothing is more simple today than plugging a USB key, an external disk or a memory card into a computer to retrieve files from it or copy new ones.