iPhone Camera unsupported file system APFS after iOS 18 upgrade

Now Apple has written it into the support document

About Apple ProRes on iPhone - Apple Support

Record ProRes files to an external storage device

With iPhone 15 Pro models and iPhone 16 Pro models, you can connect an external storage device with USB-C to store or record your ProRes files directly on an external storage device. Here are a few things to keep in mind:

• Your external storage device must be formatted with exFAT. Password-encrypted drives aren't supported.
• Use a USB 3 cable with speed of at least 10 Gbits per second.
• Your external storage device must write at speeds of at least 220 MB per second for 4K60 ProRes and at least 440MB per second for 4K120 ProRes. If you attach a slower external storage device, you might get a Slow Recording Speed message.
• Use the Files app to format your external storage device and manage your ProRes files. You must re-format your external storage device before beginning each 4K120 ProRes recording session to ensure optimal performance.
• To record to your iPhone, disconnect the external storage device.

I've been trying this out for a few days and think I sorted it. Will share my process below:

• I formatted the external SSD on my macbook to be ExFAT and it wouldn't show on my iPhone 16 Pro.
• Reformatted it to be APFS and my iPhone 16 Pro would read it but not allow for filming in ProRes as it stated it needed to be formatted into ExFAT in order to record to external SSD (as mentioned by others below).
• I went into my files app on my phone and erased and formatted the SSD, through my phone, and changed it to ExFAT.
• This seemed to work as the drive was formatted on the iPhone and not via connecting to a macbook. This worked for me and now is allowing me to film in ProRes and showing up in the files section on my phone.

Hope that helps some people and saves them the headache I had!

Note that if you are shooting ProRes video to an external drive, it must be formatted in exFAT:

* Your external storage device must be formatted with exFAT. Password-encrypted drives aren't supported.

About Apple ProRes on iPhone - Apple Support

When my external Cosair mp600 1TB SSD is formatted to APFS my iPhone 15pro displays the message "ProRes Not Supported - ProRes 4k and 1080P at 60 fps are only supported when recording to external storage devices." When I format to exFat I have no problem. Very frustrating. When formatted to APFS I can transfer photos to it from my iPhone photo library though. Strange.

Same issue here. Bought a new Kingston PCIe NVMEe SSD. Formatted for APFS. Works great on my iMac but when I try to record direct to the Kingston SSD from my iPhone 16 Pro Max I am unable to and I get that exact error. "Unsupported File System. External storage devices must be formatted exFAT to supported external recording."

I can however move videos recorded on my iPhone to that SSD. So I can use the APFS ssd to offload files only.

Also, I have a GLYPH SSD that is formatted for Mac OS extended and that allows me to record video directly to it. It is not exFAT.

If you continuously see this issue, let Apple know here:

Feedback - iPhone - Apple

or contact Support directly:

Contact - Official Apple Support

Im running into the same issue, I can't view the files, and neither can I record into my ssd directly.

and it seems like this is the only post on the internet regarding this issue?

I could reformat my ssd to exfat but it's gonna take a loooong time to backup and transferring back the data, has anyone resolved this issue?