A drive formatted on Windows is often read-only on a Mac; a drive formatted on a Mac often doesn't show up on Windows at all. The fix is choosing a format both understand.
Which format to choose
| Format | Mac | Windows | Use it when |
|---|---|---|---|
| exFAT | Read and write | Read and write | The drive moves between Mac and Windows — the usual choice |
| FAT32 (MS-DOS FAT) | Read and write | Read and write | Old devices (cameras, car radios, TVs) need it; no file can be larger than 4 GB |
| NTFS | Read only (by default) | Read and write | The drive stays mainly on Windows |
| APFS, Mac OS Extended | Read and write | Not without extra software | The drive stays on Macs (and for Time Machine) |
For a drive you carry between a Mac and a Windows PC, exFAT is the answer: both read and write it, and there's no 4 GB limit.
Format the drive as exFAT on a Mac
Formatting erases everything on the drive. Copy what you need first.
- Open Disk Utility (Applications ▸ Utilities).
- Choose View ▸ Show All Devices and select the drive itself (the top entry for that drive, not a volume under it).
- Click Erase, enter a name, choose ExFAT as the format and GUID Partition Map as the scheme, and click Erase.
Or format it on Windows
In File Explorer, open This PC, right-click the drive, choose Format…, set the file system to exFAT and click Start. (Windows' Format dialog doesn't offer FAT32 for drives over 32 GB.)
Good to know
- Always eject before unplugging (on a Mac: the eject button next to the drive in Finder; on Windows: Safely Remove Hardware). exFAT has no journal, so a drive pulled out mid-write is more likely to end up with errors — and macOS may then mount it read-only. Disk Utility's First Aid can usually repair it.
- Files over 4 GB won't copy to a FAT32 drive. If a large video or disk image fails to copy to a USB stick, check whether it's FAT32 and reformat it as exFAT.
- Keeping NTFS? If the drive is full of data and has to stay NTFS, an NTFS driver for Mac, such as our own CrossDriver NTFS for Mac, adds write support. See also Why is my external drive read-only on Mac?
See every drive's format at a glance
In CrossDriver Files, a free file manager for Mac that works like Windows File Explorer, every drive under This Mac shows its format — APFS, HFS+, exFAT, FAT, NTFS — and "Read-only" right in the navigation pane, and Home shows capacity bars and free space. You know before you start copying whether a drive will work on the other computer.
