iPhone 15 not mounting external HDD in Files

Question

Level 1

4 points

iPhone 15 not mounting external HDD in Files

Hi, I’m having a very frustrating issue with my external HDD on my iPhone 15.

My HDD is 1 TB, mechanical, connected via a dock (USB-A from HDD → dock → USB-C to iPhone).
The HDD worked perfectly twice — iPhone mounted it, I could access and transfer files.
After disconnecting and reconnecting, iPhone recognizes the accessory (shows “connected”), but it doesn’t appear in Files anymore.
The HDD spins normally and works on other computers. No files are lost.
The HDD is formatted exFAT (currently), but I know iOS is picky about Apple-friendly formatting.
I’ve tried rebooting iPhone, different cables, turning Files app off and on — nothing works.

Has anyone experienced this exact problem? Is there a reliable way to make the iPhone consistently mount a mechanical HDD after it worked once?

Thanks for any guidance!

iPhone 15, iOS 26

Posted on Mar 7, 2026 10:41 PM

Answer 1

Top-ranking reply

Barryukuk Author

Level 1

4 points

Mar 8, 2026 7:31 PM in response to LotusPilot

Thanks, yep. I’ve just realised my iPhone wasn’t supplying enough power. Once I plugged the dock into the wall socket, it sped up straight away. I’d formatted it in exFAT before, so I reformatted it to APFS just to make sure everything runs smoothly

Answer 2

LotusPilot

Level 10

334,506 points

Mar 8, 2026 4:36 PM in response to Barryukuk

HDD drives are notoriously power hungry.

Unless your HDD is self-powered from its own power supply, or your USB hub powers the HDD via its USB connection, it may not reliably/consistent work with your iPhone - if it works at all. You iPhone alone may not be able to source sufficient power to reliably power-up the HDD via the USB hub.

Answer 3

LotusPilot

Level 10

334,506 points

Mar 9, 2026 3:28 AM in response to Barryukuk

I'm delighted that the problem has been identified and easily resolved by following the provided advice.

Be aware that while using a journalling file system may reduce the possibility of file corruption due to an incomplete write, changing the HDD format from exFAT to APFS will do nothing to reduce the power requirements to run the HDD.

If intending to use external storage options with your iPhone when away from line-power, you would be well advised to consider using solid state storage - such as a portable SSD or thumb-drive.

Answer 4

Tesserax

Level 10

162,294 points

Mar 9, 2026 10:54 AM in response to Barryukuk

Just so you are aware, APFS was designed specifically for SSDs, not HDDs as there are no performance enhancements using this format type for HDDs. On the other hand, ExFAT should work fine with either drive type.

iPhone 15 not mounting external HDD in Files

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