External drives · Mounting and drive problems
What does "Disk Not Ejected Properly" mean on a Mac?
Short answer: macOS lost the drive while it was still in use — usually because it was unplugged without ejecting, or a cable, hub or power problem dropped the connection. Eject first; if it happens on its own, connect directly with another cable and run First Aid.
It means macOS lost contact with a drive while the drive was still in use — it was unplugged, lost power or dropped its connection before macOS had finished with it. The warning is a reminder, not a diagnosis: usually nothing was damaged, but anything being written at that moment may be incomplete.
Common causes:
- Pulling the cable without ejecting first.
- A loose cable, a hub or dock that resets, or a hub that cuts power when the Mac sleeps.
- A bus-powered drive that isn't getting enough power.
- The drive itself going to sleep or overheating.
If it happens once after an unplug, eject properly next time. If it happens on its own, connect the drive directly to the Mac with a different cable, then run First Aid in Disk Utility. See why the drive keeps disconnecting.