External drive read-only on Mac, or write-protected on Windows? NTFS, exFAT and the fixes
You can open the drive and see your files, but you can't copy anything onto it, delete anything, or rename a folder. Usually the drive is fine. It's the format, a lock switch, or a safety flag.
Why it happens
| What you see | Likely cause | Fix |
|---|---|---|
| Mac: Get Info says "You can only read", Format is NTFS | macOS reads NTFS, the Windows format, but doesn't write it. | Copy the files off, erase as exFAT, copy them back. Or keep NTFS and copy files on from a Windows PC. |
| Mac: the drive opens, copying fails with a permissions error, Format is APFS or Mac OS Extended | File ownership from another Mac. | Cmd+I, click the padlock, tick "Ignore ownership on this volume". |
| Mac: a drive that used to work is now read-only, Disk Utility shows errors | macOS mounted it read-only to protect a damaged file system. | Back up what you can, then run First Aid in Disk Utility. |
| Windows: "The disk is write-protected" on an SD card | The little lock slider on the card or adapter is pushed down, or it moved as you pushed it in. | Slide it up towards the contacts and reinsert gently. A worn adapter whose slider won't stay put is worth replacing. |
| Windows: "write-protected" on a USB stick or drive | A read-only flag on the disk, or a policy set by work software. | Clear the flag with diskpart (below). On a work laptop, ask IT: blocking USB writes is often deliberate. |
| Read-only everywhere, even after clearing the flag, or files come back after you delete them | Flash memory at the end of its life. Many sticks and cards lock themselves read-only on purpose so you can still rescue the data. | Copy everything off and replace it. Formatting won't bring it back. |
Move an NTFS drive to exFAT without losing files
- Copy everything on the drive to the Mac or another drive, and check the copy opens.
- Open Disk Utility, choose View, Show All Devices, and select the drive itself (the top line, not the volume under it).
- Click Erase. Format: ExFAT. Scheme: GUID Partition Map. Erasing deletes everything on it, which is why step 1 comes first.
- Copy the files back. The drive now works for writing on both Mac and Windows, and on most TVs and consoles.
Prefer to keep NTFS, for example because a Windows backup program needs it? Commercial NTFS drivers for macOS add write support. Old tips that turn on Apple's hidden NTFS writing through Terminal are best avoided: it was never finished and can corrupt the drive.
Which format should a drive use?
| Format | Windows | Mac | Biggest single file | Good for |
|---|---|---|---|---|
| exFAT | Read and write | Read and write | No practical limit | Sticks and drives that move between computers |
| NTFS | Read and write | Read only | No practical limit | Drives that live on Windows, Windows backups |
| APFS / Mac OS Extended | Not readable without extra software | Read and write | No practical limit | Time Machine and Mac-only drives |
| FAT32 | Read and write | Read and write | 4 GB minus 1 byte | Very old devices, some car stereos |
Clear a read-only flag on Windows
Open Command Prompt as administrator and type these one at a time. Check the size column carefully so you pick the USB drive, not your main disk.
diskpart
list disk
select disk 2
attributes disk clear readonly
exitIf diskpart reports the flag is cleared but writing still fails, the drive itself has locked up. Copy your files off while it still reads.
Related
Write-protected on every computer? · Windows says a Mac drive needs formatting · FAT32 vs exFAT vs NTFS, device by device · Mac won't eject an external drive · USB stick or external drive not showing up · File too large for the destination file system (FAT32) · SD card not showing up · Back up phone photos to an external drive · What is a file system? (Wirebook)
Questions
Why is my external hard drive read-only on my Mac?
Almost always because it's formatted NTFS, the Windows format. macOS can read NTFS but not write it. Copy the files off and reformat it as exFAT, or add a commercial NTFS driver.
Can I make an NTFS drive writable on a Mac for free?
Not reliably. The hidden built-in option is unfinished and can corrupt files. The safe free route is reformatting to exFAT after copying the data off.
Will formatting to exFAT delete my files?
Yes. Erasing a drive in any format deletes what's on it, so copy everything off first and check the copy before you erase.
How do I remove write protection from a USB stick?
Check for a lock switch first, then clear the read-only flag with diskpart (attributes disk clear readonly). If it's still read-only after that, the stick has likely worn out and locked itself to protect your data.
Is exFAT or NTFS better for an external drive?
exFAT if it moves between Windows and Mac or plugs into a TV. NTFS if it only ever lives on Windows, since it copes better with a sudden unplug.
Published .