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Unable to read an exFAT USB key

My Mac mini M1 (OS Monterey) would, for some reason, not recognise exFat USB data key. It does not show in Finder, neither in Disk Utility. But I can read and write to it on my separate MacBook Pro (late 2015, OS Monterey). Is there anything specific that I should know as I shuffle plenty of data/files between Mac and windows. Thanks in advance.

Posted on Nov 7, 2021 5:47 PM

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Question marked as Top-ranking reply

Posted on Nov 8, 2021 1:33 AM

It seems 128 kB Allocation Unit Size should be used if exFAT is used on a Mac.


https://joshuatj.com/2015/05/13/how-to-format-your-hard-drive-hdd-for-mac-os-x-compatibility-with-the-correct-exfat-allocation-unit-size/


https://www.partitionwizard.com/partitionmagic/allocation-unit-size-exfat.html


I have used exFAT formatted with Windows 10 default formatting options. The only problem was that a 128 GB flash drive formatted as exFAT (GUID) on Big Sur was seen only AFAIR 100 MB on Windows 10 while exFAT (Master Boot Record) showed all capacity.


And currently Monterey 12.0.1 is reported to have problems with some vendor's USB drives. And M1 Macs are reported to have problems with NTFS drives.

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Question marked as Top-ranking reply

Nov 8, 2021 1:33 AM in response to Janez Premoze

It seems 128 kB Allocation Unit Size should be used if exFAT is used on a Mac.


https://joshuatj.com/2015/05/13/how-to-format-your-hard-drive-hdd-for-mac-os-x-compatibility-with-the-correct-exfat-allocation-unit-size/


https://www.partitionwizard.com/partitionmagic/allocation-unit-size-exfat.html


I have used exFAT formatted with Windows 10 default formatting options. The only problem was that a 128 GB flash drive formatted as exFAT (GUID) on Big Sur was seen only AFAIR 100 MB on Windows 10 while exFAT (Master Boot Record) showed all capacity.


And currently Monterey 12.0.1 is reported to have problems with some vendor's USB drives. And M1 Macs are reported to have problems with NTFS drives.

Unable to read an exFAT USB key

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