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How to restore USB flash drive back to full capacity on Mac? Help!

Hey everyone, I recently bought a genuine 256GB SanDisk USB drive. Initially, it showed the full capacity of 256GB even after reformatting to ExFAT. However, after using it to create a bootable drive, I was shocked to find that the capacity had mysteriously reduced to only 6GB. I tried using Disk Utility to erase the drive completely, but it still remained at 6GB. The partition icon is now greyed out and unusable. I'm stuck and unsure how to reformat the drive and regain its original capacity. It was quite an expensive USB drive, so any ideas or suggestions would be greatly appreciated. Thanks in advance for your assistance!

Best Answered by

iBoysoft author Jenny Zeng

Jenny Zeng

Answered on Wednesday, May 31, 2023

It seems that your USB drive's size reduced after making it a bootable drive and you are unable to reformat it to regain its full capacity. I suspect you're not formatting the drive correctly. The following is the correct way to do it.

How to restore a USB drive back to full capacity on Mac:

  1. Open Disk Utility.
  2. Click View > Show All Devices to reveal the physical drive.
  3. Select your USB drive that's not showing full capacity from the left side.
  4. Click the Erase button.
  5. Type a name for your drive.
  6. Choose a format for it. (Mac OS Extended or APFS if you only need to use it on your Mac.)
  7. Select GUID Partiiton Map as scheme.
  8. Click Erase.
  9. Wait for the erase process to complete.

After that, your USB drive should show its full capacity.


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