Which drive format works with iPhone, Mac and Windows?

For a drive you use with iPhone, Mac and Windows, choose exFAT. For iPhone and Mac only, APFS is another option. Check the existing format first: you may not need to erase anything.

Diagram: one external drive, one data partition; exFAT for all three systems or APFS for Apple devices.

Check the format first

Mac: open Disk Utility, select the external volume and read its format in the information panel.
Windows: File Explorer → This PC → right-click the external drive → Properties → File system.
iPhone: Files → Browse → Locations → your drive. Try opening a file before choosing the drive in an app.

Sources: Microsoft.

Which formats work?

Format	iPhone / iPad	Mac	Windows
exFAT	Yes	Yes	Yes
APFS	Yes	Yes	No native support
HFS+	Yes	Yes	No native support
FAT32	Yes	Yes	Yes
NTFS	Not listed by Apple	Read only	Yes

This table describes built-in operating-system support, without extra drivers. Apple lists APFS (encrypted) and HFS+ as supported too. An encrypted volume must be unlocked before use. A format supported by the OS still needs testing with the app and your drive. FAT32 cannot hold a single file of 4 GiB or more. NTFS is not in Apple’s supported list for iPhone.

Apple requires a single data partition for an external drive connected to iPhone. An APFS volume and a partition are different things; for a newly prepared photo drive, keep the layout simple: one data partition and one volume.

Sources: Apple (iPhone), Apple (Mac), Microsoft, Seagate (NTFS / HFS+).

What format does a new drive use?

Capacity and the words “SSD” or “for Mac” do not tell you the format. These manufacturer examples apply to the listed models; check your own drive, especially if it has been used before.

Model	Factory format
Samsung Portable SSD	exFAT
Seagate Backup Plus Portable	exFAT
WD My Passport · WDBYVG / WDBPKJ	NTFS
WD My Passport USB-C · WDBRMD / WDBWML	exFAT
WD My Passport for Mac · WDBP6A	HFS+

Change the format on a Mac

Disk Utility → View → Show All Devices.
Select the external physical drive at the top of its hierarchy, then Erase. This erases all its volumes. Do not select the Mac’s internal drive.
Choose GUID Partition Map and exFAT, or APFS for Apple devices only. Give it a name such as USB DRIVE.
Confirm Erase, wait for completion and eject the drive. Reconnect it to iPhone and check it in Files.

Sources: Apple.

Diagram of the Erase dialog in Disk Utility.

Change the format on Windows

For a drive that already has one data partition: File Explorer → This PC → right-click the correct external drive → Format.
Choose exFAT, keep the default allocation size, check the drive again and start formatting.
Formatting a volume does not remove other partitions. If the disk has several, back up all of them and use Disk Management to prepare one data volume, or use the Mac steps above.
Safely eject the drive, connect it to iPhone and check it in Files.

Sources: Microsoft.

If iPhone cannot open the drive

Check Files first. If it cannot open the drive either, solve that connection or disk problem before retrying PicFrom.
Try a data-capable cable and a suitable adapter. A drive may need a powered USB hub; Lightning devices may need a Lightning to USB 3 Camera Adapter with power connected.
Check the format and partition layout on a computer. Do not erase a drive just because you see “Content Unavailable”: that message does not establish the cause.
Back up readable files before repair or repartitioning. If you start over, prepare one data partition. We observed this resolve one two-partition SSD case, but did not establish its exact cause.