Caution: macOS Sonoma May Not Support ExFAT

Posted on November 4, 2023 by Larry Jordan

UPDATE Jan. 4, 2024. On macOS Sonoma 14.2.1, I can format and access ExFAT-formatted SSDs and thumb drives. Hopefully, this means Apple has fixed this problem.

Mary Peterson sent me the following caution:

“Had a couple exFAT formatted drives (in case I had to share with PC client). But Sonoma is unable to mount those drives. Lots of discussion in Apple Community forums on the issue. Ended up using EaseUS software which could see into the drives and let me copy them. Some files were corrupted but was able to copy all my video clips and more. Am now making sure drives are formatted APFS. And I bought lots of cheapish external drives so I can keep 3 copies of critical files! I should have known better…”

In researching this, it appears that there are issues with ExFAT in Sonoma. Here’s a link to Apple Discussions on this topic.

Apple’s Sonoma Release Notes state:

“The implementations of the exfat and msdos file systems on macOS have changed; these file systems are now provided by services running in user-space instead of by kernel extensions. If the application has explicit checks or support for either the ExFAT or MS-DOS file systems, validate the applications with those file systems and report any issues.”

In other words, there were issues, but these may now be fixed. Maybe.

If you have critical data stored on ExFAT drives, BE SURE to copy it to a non-ExFAT volume before upgrading. It is better to be safe than sorry.

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23 Responses to Caution: macOS Sonoma May Not Support ExFAT

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Mark Roseman says:

November 18, 2023 at 2:50 pm

On Sonoma rsync and cp are both not working properly with ex-fat. Rsync gives all copied files today’s date and does not retain the original file date. This has affected the wonderful copy app dropsync. At the moment, it can be used only with external drives in apple native formats.
Larry Jordan says:

November 18, 2023 at 7:19 pm

Mark:

Good to know. Thanks,

Larry
Patrick M Blackard says:

December 4, 2023 at 11:49 am

I’ve been using MacDrive on Windows machines for 15 years. I can keep my files in Mac formats (including APFS) and use them on either machine. In that time editing has been on Windows Avid, Mac Final Cut, Mac Premiere, and now Windows Premiere. Field transfer is on an M1 MacBook Pro. When I send camera footage to clients, they mostly want Mac formatted files.
Larry Jordan says:

December 4, 2023 at 11:52 am

Thanks!

Larry
Rick Lee says:

December 4, 2023 at 3:37 pm

ExFAT drives seem to work fine in Sonoma (I’m using 14.1) if you format it with Allocation Unit Size to 128K. To do that in Windows, use Disk Manager, Format, and set the Allocation Unit Size to 128K (don’t use Default, it’s 1024K in Windows).

Cheers.
chris says:

December 11, 2023 at 3:54 am

Thanks buddy. That has solved the problem for me. I’m not sure what Allocation Unit Size defaulted to when I formatted it originally in Monterey, but doing it in Windows, with 128K, has worked. Thank you for posting.
chris says:

December 13, 2023 at 12:30 pm

Further to this.. It works. but it is painfully slow for me. approx 10 times slower with the same external SSD – Samsung T5. Was approx 1GB/s, now 0.1GB/s. This is for a small number of large files.
Although it does work.
chris says:

December 13, 2023 at 12:40 pm

I formatted again in Sonoma as exFat and it’s fine now.
Larry Jordan says:

December 13, 2023 at 12:55 pm

Chris:

Thanks for the update.

Larry
Ed says:

April 13, 2024 at 5:39 am

So in summary if I partition an external drive to exFat for the Windows files i should be able to read and write to the exFat files from a MacBookPro [2021 M1].