We Explain: Why Your Flash Drive is Not Readable on a Mac and What You Can Do About It

We Explain: Why Your Flash Drive is Not Readable on a Mac and What You Can Do About It
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A Guide to Jump-Starting Your Flash Drives on Mac

Flash drives are one of the most used on the go data solutions and are used in combination with a variety of computers and operating systems. It may occur that a flash drive becomes unreadable on a Mac computer, which is a worst-case scenario for many. There are a variety of reasons why your drive is not readable anymore. We will take a look at a few of the most common…

Why Does My Mac Refuse My USB Stick?

There are a many reasons why a thumb drive would not be recognized by the Mac computer. Although it might scare you at first, most of the possible explanations will not result in you losing all of your saved data. These include the following:

  • The most likely reason is that the flash drive is not formatted in a Mac supported format. The OS X operating system can read HSF, HSF + and Fat32 file formats. Windows’ NTFS and Linux’s EXT file formats are by default not supported, which could cause your thumb drive not to show up.
  • The USB Drive has become corrupted by not properly ejecting it. When a flash drive is not properly un-mounted it can become corrupted. This will cause the flash drive to become unreadable by the Mac computer.
  • The OS X operating system is unable to mount the drive. This is an error within the operating system, which will require a manual mount.
  • Although highly unlikely but there is always the possibility that the USB port itself is broken on your Mac computer.

Whatever the reason it cannot be read, there are fixes available that will help you save your data and restore your drive to a working state.

Getting Your USB Drive Back Into Shape and Working on Your Mac

Formatting the Thumb Drive on Mac

The above mentioned issues will all have you worrying a bit but can be either avoided or fixed. Here are the corresponding instructions on how to properly recover your thumb drive:

  • You need to format your drive in a OS X supported format. This can be done through the disk utility of your Mac, but will make you lose your data. Therefore it is essential to first empty the drive of all its data on a supported Linux or Windows machine. In Disk Utility select the drive on the left and select ‘Erase’ in the right panel. Select the disc format you want for you drive and select Erase.
  • When your thumb drive is corrupted you can try to fix it by going to Disk Utility, selecting the drive on the left and browsing to the ‘First Aid’ tab. Here you can select the ‘Repair Disk’ option to see if it can be saved. If not you can either try on a different computer (or Windows/Linux) or format it. A corrupt disc is always the worst-case scenario.
  • You can try to mount the thumb drive manually by opening the Disk Utility tool. Again, select the USB thumb drive, which should be recognized but not mounted. Select ‘Mount’ in the top bar after which the thumb drive should be ready to use.

All the above mentioned solutions should in theory get your USB drive up and running again. In my experience these drives can behave rather unpredictably and simple rebooting your computer can make a difference as well. If your USB Stick is usually working without issues, there is no real reason to think you will lose your data, as there is probably a relatively simple solution. Whatever the problem is, good luck!

Note. Have you occurred a USB stick issue on your Mac and find a different solution to the problem, feel free to post in the comment section!


  • Author’s own experience and knowledge.
  • All Screenshots by the Author.