External drives · Drive formats

Why is my external drive read-only on my Mac?

Short answer: Usually it's NTFS (read-only on a Mac), macOS mounted it read-only after finding errors (run First Aid), a permissions setting in Get Info, or a lock switch. Storage Studio needs a writable drive.

The most common reasons:

  • It's NTFS — macOS reads Windows NTFS drives but can't write to them. Erase it as APFS (after backing up) to use it.
  • macOS found file-system errors and mounted it read-only to protect your data — run First Aid in Disk Utility.
  • Permissions — in Finder, choose Get Info on the drive and check the Sharing & Permissions section.
  • A physical lock switch on some SD cards and older drives.

Storage Studio needs to write to the drive, so a read-only drive can't be set up or used for moves; the speed test will also fail on it.

Last reviewed

Related questions

Also available as Markdown and JSON.