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External Drive Read-Only
I plugged my USB drive into the MacBook, opened it in Finder, and tried to save a file. "The volume is read only." Tried dragging a file onto the drive. Same error. Checked properties. Nothing. The drive had been working on my Windows desktop five minutes earlier.
I Googled "Mac external drive read only" and got approximately forty forum posts from people who had the same reaction I did: "Is my drive broken?"
It's not broken. It's formatted as NTFS. And macOS has been throwing shade at NTFS since 2007.
What's Happening
NTFS is the default file system on Windows. macOS can read NTFS drives. It cannot write to them. Apple has had read-only NTFS support for nearly two decades and has never added write support. No error message explains this. Finder just silently refuses to let you save, copy, or create anything. It treats your drive like a museum exhibit: look but don't touch.
Windows users format drives as NTFS because that's what Windows defaults to. Mac users format drives as APFS because that's what Mac defaults to. Neither platform fully supports the other's format. This is the tech equivalent of two countries refusing to use the same electrical outlet. Both could fix it. Neither will.
The Solutions
| Approach | Cost | Downside | Best For |
|---|---|---|---|
| Reformat to exFAT | Free | Erases everything on the drive | Drives you use on both platforms |
| Paragon NTFS for Mac | ~$20 | Paid software, runs in the background | Keeping NTFS without erasing |
| Tuxera NTFS | ~$15 | Same tradeoff as Paragon | Alternative to Paragon |
| Keep a separate drive | Free | You now carry two drives | When you can't erase the drive |
How to Reformat to exFAT
Back up everything on the drive first. Reformatting erases it. All of it. Gone.
Cmd + Space, type Disk Utility, press Enter- Select the external drive in the sidebar (the physical device, not the volume underneath it)
- Click Erase
- Name it whatever you want
- Set Format to exFAT
- Set Scheme to GUID Partition Map
- Click Erase
exFAT works on Mac, Windows, and Linux. No file size limits (unlike FAT32's hilarious 4GB cap in 2025). No third-party software. It's the Switzerland of file systems.
How to Tell What Format a Drive Is
Select the drive in Finder, press Cmd + I (Get Info). Look for "Format" in the General section. If it says NTFS, that's your problem.
Windows Comparison
| Concept | Windows | Mac |
|---|---|---|
| Default format | NTFS | APFS |
| NTFS support | Full read/write | Read only |
| exFAT support | Full read/write | Full read/write |
| APFS support | None (without third-party tools) | Full read/write |
| Format a drive | Right-click > Format | Disk Utility > Erase |
Both platforms refuse to fully support each other's file system. Apple won't write NTFS. Windows won't read APFS. It's petty. exFAT is the peace treaty. Format your shared drives as exFAT and move on with your life.