External drive not mounting on a Mac? Get your files off it first

1. Rule out the simple causes

• Try a different cable and a different port, and plug straight into the Mac instead of a hub or dock.
• Large spinning drives can need more power than a bus-powered port gives. Use the drive’s own power supply if it has one.
• Open Disk Utility, choose View > Show All Devices, and see whether the physical drive appears, even if its volume is greyed out.
• In Terminal, diskutil list shows every disk macOS can talk to. If the drive isn’t listed at all, the problem is the connection, the enclosure or the hardware, not the file system.

2. What not to do

• Don’t click Initialise or Erase when macOS offers to. That creates a new, empty file system on top of your data.
• Don’t run First Aid again and again. Repair tools write to the drive. On a drive that is physically failing, every repair attempt is more wear and more risk. Copy first, repair later.
• Don’t save anything onto the drive, including recovered files.

3. Copy your files off with Retrova

Retrova reads the drive itself instead of asking macOS to mount it. It understands APFS, NTFS, FAT12/16/32, exFAT, ext2/3/4, XFS and Btrfs, and finds the partitions on GPT and MBR disks. It opens the drive read-only: nothing is written, repaired or mounted.

1. Plug the drive in and open Retrova. On the home screen choose A drive won’t open. Retrova lists every drive and partition it can see, with the file system it detected and a health check where the drive reports one.
2. Pick the drive or partition. Reading a drive directly needs administrator rights, so Retrova asks for your password at this point and only uses it to read.
3. Browse and choose what you want back. You see the original folders and file names. Select whole folders or single files, and preview photos, videos, PDFs and text before copying.
4. Choose where the copies go. Always pick a different drive with enough free space. Retrova never saves onto the drive it’s rescuing, and it pauses by itself if the destination runs low on space.
5. Copy, then verify. Files are written as temporary parts and renamed only when complete, so a half-copied file never looks finished. Anything unreadable is logged and the copy carries on. When it’s done, run Verify to compare every copied file with the original, byte for byte.

4. If the drive clicks, grinds or keeps disconnecting

Then time matters more than anything. Use Retrova to copy the whole drive to an image first: it reads every block once, retries unreadable spots in small pieces, notes anything it couldn’t read, and can resume if the drive drops out. Then recover from the image file, which never gets tired. See recovering from a failing drive.

5. When Retrova can’t help

If the drive doesn’t appear in diskutil list on any computer, or makes repeated clicking or grinding noises, the hardware itself has failed. Stop powering it on and talk to a professional data recovery lab. Mac OS Extended (HFS+) volumes can’t be browsed yet, but Deep scan can still find photos, videos and documents on them.

Questions

Related guides

• Recover files from an APFS drive that macOS won’t mountFirst Aid failed and the volume stays greyed out? Read the APFS structures directly and copy everything off.
• How to check a copy is perfect: verify files byte for byteCopies fail silently. Check recovered files against the original by size, by spot check, or every byte, with checksums.
• Recover files from a failing hard drive: image it firstSlow, clicking or disconnecting? Read every block once into an image, retry the bad ones last, then recover from the image.